Assoc. Prof. Katarzyna Pietrzak, Ph.D., Dr. Habil., Eng.

Department of Mechanics of Materials (ZMM)
Division of Advanced Composite Materials (PZMK)
position: professor IPPT
telephone: (+48) 22 826 12 81 ext.: 456
room: 144
e-mail: kpietrzak

Recent publications
1.Chmielewski M., Pietrzak K., Teodorczyk M., Nosewicz S., Jarząbek D., Zybała R., Bazarnik P., Lewandowska M., Strojny-Nędza A., Effect of metallic coating on the properties of copper-silicon carbide composites, APPLIED SURFACE SCIENCE, ISSN: 0169-4332, DOI: 10.1016/j.apsusc.2016.12.130, Vol.421, pp.159-169, 2017
Chmielewski M., Pietrzak K., Teodorczyk M., Nosewicz S., Jarząbek D., Zybała R., Bazarnik P., Lewandowska M., Strojny-Nędza A., Effect of metallic coating on the properties of copper-silicon carbide composites, APPLIED SURFACE SCIENCE, ISSN: 0169-4332, DOI: 10.1016/j.apsusc.2016.12.130, Vol.421, pp.159-169, 2017

Abstract:
In the presented paper a coating of SiC particles with a metallic layer were used to prepare copper matrix composite materials. The role of the layer was to protect the silicon carbide from decomposition and dissolution of silicon in the copper matrix during the sintering process. The SiC particles were covered by chromium, tungsten and titanium using Plasma Vapour Deposition method. After powder mixing of components, the final densification process via Spark Plasma Sintering (SPS) method at temperature 950C was provided. The almost fully dense materials were obtained (> 97.5%). The microstructure of obtained composites was studied using scanning electron microscopy as well as transmission electron microscopy. The microstructural analysis of composites confirmed that regardless of the type of deposited material, there is no evidence for decomposition process of silicon carbide in copper. In order to measure the strength of the interface between ceramic particles and the metal matrix, the micro tensile tests have been performed. Furthermore, thermal diffusivity was measured with the use of the laser pulse technique. In the context of performed studies, the tungsten coating seems to be the most promising solution for heat sink application. Compared to pure composites without metallic layer, Cu-SiC with W coating indicate the higher tensile strength and thermal diffusitivy, irrespective of an amount of SiC reinforcement. The improvement of the composite properties is related to advantageous condition of Cu-SiC interface characterized by well homogenity and low porosity, as well as individual properties of the tungsten coating material.

Keywords:
metal matrix composites, silicon carbide, metallic layers deposition, thermal conductovity, interface strength

2.Nosewicz S., Rojek J., Chmielewski M., Pietrzak K., Discrete element modeling and experimental investigation of hot pressing of intermetallic NiAl powder, ADVANCED POWDER TECHNOLOGY, ISSN: 0921-8831, DOI: 10.1016/j.apt.2017.04.012, Vol.28, pp.1745-1759, 2017
Nosewicz S., Rojek J., Chmielewski M., Pietrzak K., Discrete element modeling and experimental investigation of hot pressing of intermetallic NiAl powder, ADVANCED POWDER TECHNOLOGY, ISSN: 0921-8831, DOI: 10.1016/j.apt.2017.04.012, Vol.28, pp.1745-1759, 2017

Abstract:
This paper presents the numerical and experimental analysis of hot pressing of NiAl powder with an emphasis on the best possible representation of its main stages: initial powder compaction and pressure-assisted sintering. The numerical study has been performed within the discrete element framework. In the paper, an original viscoelastic model of hot pressing has been used. In order to ensure that the applied values of material parameters in numerical simulations are appropriate, the reference literature has been reviewed. It produced the relations and equations to estimate the values of all required sintering material parameters of the considered viscoelastic model. Numerical simulations have employed the geometrical model of the initial dense specimen generated by a special algorithm which uses the real grain distribution of powder. The numerical model has been calibrated and validated through simulations of the real process of hot pressing of intermetallic NiAl material. The kinetics of compaction, sintering and cooling stage indicated by the evolution of density, shrinkage and densification rate have been studied. The comparison of numerical and experimental results has shown a good performance of the developed numerical model.

Keywords:
Powder metallurgy; Hot pressing; Sintering; Simulation; Discrete element method; Nickel aluminide

3.Nosewicz S., Rojek J., Chmielewski M., Pietrzak K., Lumelskyj D., Application of the Hertz formulation in the discrete element model of pressure-assisted sintering, GRANULAR MATTER, ISSN: 1434-5021, DOI: 10.1007/s10035-016-0699-9, Vol.19, No.1, pp.16-1-8, 2017
Nosewicz S., Rojek J., Chmielewski M., Pietrzak K., Lumelskyj D., Application of the Hertz formulation in the discrete element model of pressure-assisted sintering, GRANULAR MATTER, ISSN: 1434-5021, DOI: 10.1007/s10035-016-0699-9, Vol.19, No.1, pp.16-1-8, 2017

Abstract:
This paper presents the numerical modelling of initial powder compaction and pressure-assisted sintering performed by original viscoelastic discrete element model. The research is focused on the influence of the type of the model representing an elastic part of interparticle force. Two elastic contact models—linear and nonlinear Hertz model—have been implemented and used to analyse interaction of NiAl powder particles during compaction and sintering process. Numerical models have been validated using own experimental results. Microscopic effects (particle penetration) and macroscopic changes (relative density) have been compared. It has been shown that although both models represent properly macroscopic behaviour of the material at the sintering process, the Hertz model produces the results closer to the real experimental ones during the initial compaction stage. Evaluation of macroscopic quantities enables implementation of the discrete element model in the framework of the multiscale modelling framework which is currently developed for sintering processes.

Keywords:
Powder metallurgy, Sintering, Initial compaction, Elasticity, Discrete element method

4.Chmielewski M., Pietrzak K., Strojny-Nędza A., Jarząbek D., Nosewicz S., Investigations of interface properties in copper-silicon carbide composites, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0200, Vol.62, No.2B, pp.1315-1318, 2017
Chmielewski M., Pietrzak K., Strojny-Nędza A., Jarząbek D., Nosewicz S., Investigations of interface properties in copper-silicon carbide composites, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0200, Vol.62, No.2B, pp.1315-1318, 2017

Abstract:
This paper analyses the technological aspects of the interface formation in the copper-silicon carbide composite and its effect on the material’s microstructure and properties. Cu-SiC composites with two different volume content of ceramic reinforcement were fabricated by hot pressing (HP) and spark plasma sintering (SPS) technique. In order to protect SiC surface from its decomposition, the powder was coated with a thin tungsten layer using plasma vapour deposition (PVD) method. Microstructural analyses provided by scanning electron microscopy revealed the significant differences at metal-ceramic interface. Adhesion force and fracture strength of the interface between SiC particles and copper matrix were measured. Thermal conductivity of composites was determined using laser flash method. The obtained results are discussed with reference to changes in the area of metal-ceramic boundary.

Keywords:
copper matrix composites, silicon carbide, interface, thermal conductivity, adhesion

5.Strojny-Nędza A., Pietrzak K., Teodorczyk M., Basista M., Węglewski W., Chmielewski M., Influence of Material Ccating on the heat Transfer in a layered Cu-SiC-Cu Systems, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0199, Vol.62, No.2B, pp.1311-1314, 2017
Strojny-Nędza A., Pietrzak K., Teodorczyk M., Basista M., Węglewski W., Chmielewski M., Influence of Material Ccating on the heat Transfer in a layered Cu-SiC-Cu Systems, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.1515/amm-2017-0199, Vol.62, No.2B, pp.1311-1314, 2017

Abstract:
This paper describes the process of obtaining Cu-SiC-Cu systems by way of spark plasma sintering. A monocrystalline form of silicon carbide (6H-SiC type) was applied in the experiment. Additionally, silicon carbide samples were covered with a layer of tungsten and molybdenum using chemical vapour deposition (CVD) technique. Microstructural examinations and thermal properties measurements were performed. A special attention was put to the metal-ceramic interface. During annealing at a high temperature, copper reacts with silicon carbide. To prevent the decomposition of silicon carbide two types of coating (tungsten and molybdenum) were applied. The effect of covering SiC with the aforementioned elements on the composite’s thermal conductivity was analyzed. Results were compared with the numerical modelling of heat transfer in Cu-SiC-Cu systems. Certain possible reasons behind differences in measurements and modelling results were discussed.

Keywords:
copper matrix composites, silicon carbide, interface, thermal conductivity, modelling

6.Chmielewski M., Pietrzak K., Strojny-Nędza A., Kaszyca K., Zybala R., Bazarnik P., Lewandowska M., Nosewicz S., Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique, SCIENCE OF SINTERING, ISSN: 0350-820X, DOI: 10.2298/SOS1701011C, Vol.49, pp.11-22, 2017
Chmielewski M., Pietrzak K., Strojny-Nędza A., Kaszyca K., Zybala R., Bazarnik P., Lewandowska M., Nosewicz S., Microstructure and thermal properties of Cu-SiC composite materials depending on the sintering technique, SCIENCE OF SINTERING, ISSN: 0350-820X, DOI: 10.2298/SOS1701011C, Vol.49, pp.11-22, 2017

Abstract:
The presented paper investigates the relationship between the microstructure and thermal properties of copper–silicon carbide composites obtained through hot pressing (HP) and spark plasma sintering (SPS) techniques. The microstructural analysis showed a better densification in the case of composites sintered in the SPS process. TEM investigations revealed the presence of silicon in the area of metallic matrix in the region close to metal ceramic boundary. It is the product of silicon dissolving process in copper occurring at an
elevated temperature. The Cu-SiC interface is significantly defected in composites obtained through the hot pressing method, which has a major influence on the thermal conductivity of materials.

Keywords:
Metal matrix composites; Silicon carbide; Interface; Spark plasma sintering; Thermal conductivity.

7.Wejrzanowski T., Grybczuk M., Chmielewski M., Pietrzak K., Kurzydłowski K.J., Strojny-Nędza A., Thermal conductivity of metal-graphene composites, MATERIALS AND DESIGN, ISSN: 0261-3069, DOI: 10.1016/j.matdes.2016.03.069, Vol.99, pp.163-173, 2016
Wejrzanowski T., Grybczuk M., Chmielewski M., Pietrzak K., Kurzydłowski K.J., Strojny-Nędza A., Thermal conductivity of metal-graphene composites, MATERIALS AND DESIGN, ISSN: 0261-3069, DOI: 10.1016/j.matdes.2016.03.069, Vol.99, pp.163-173, 2016

Abstract:
In this paper the results of numerical simulations and experimental studies are presented which describe potential and limitation of applications of single-layer (SLG) and multi-layer (MLG) graphene for thermal conductivity enhancement (TCE) of copper. A series of composite structures were studied which are representative of most widely used systems. The influence of structural parameters on the macroscopic thermal conductivity was analyzed, both experimentally and by numerical simulations. Analytical and Finite Element Method modeling were carried out to investigate a wide range of phenomena, including the effect of copper-MLG interface, copper grain size, volume fraction, thickness and orientation of MLG platelets as well as spatial distribution of MLG defined by percolation factor. Both modeling and the experimental results show that the volume fraction of MLG regions, their size, orientation and spatial distribution may significantly affect the thermal conductivity of metal matrix composites. TCE can be obtained for the laminate-like structure or particulate composites with highly aligned MLG regions. The thermal conductivity of such composites is strongly anisotropic and enhanced in the direction perpendicular to the layers. The results obtained in this study predict that SLG will have a negative effect on the thermal conductivity of copper matrix composites.

Keywords:
Thermal conductivity, Composites, Graphene, Finite element method

8.Chmielewski M., Pietrzak K., Basista M., Węglewski W., Rhenium doped chromium–alumina composites for high-temperature applications, International Journal of Refractory Metals and Hard Materials, ISSN: 0263-4368, DOI: 10.1016/j.ijrmhm.2015.07.012, Vol.54, pp.196-202, 2016
Chmielewski M., Pietrzak K., Basista M., Węglewski W., Rhenium doped chromium–alumina composites for high-temperature applications, International Journal of Refractory Metals and Hard Materials, ISSN: 0263-4368, DOI: 10.1016/j.ijrmhm.2015.07.012, Vol.54, pp.196-202, 2016

Abstract:
Dense chromium–alumina composites doped with rhenium have been developed by the hot pressing method (bulk composite) and plasma spraying (composite coating). The obtained materials show superior mechanical properties, insensitivity to chemically aggressive environment, good resistance to frictional wear and oxidation at elevated temperature. These enhanced properties make the Cr/Re/Al2O3 composites interesting structural materials for energy and transport applications operating in demanding service conditions, e.g. fluidal boilers in power plants or valve seats in combustion engines.

Keywords:
Metal–ceramic composites, Powder technology, Mechanical properties, Coatings

9.Zybała R., Schmidt M., Kaszyca K., Ciupiński Ł., Kruszewski M.J., Pietrzak K., Method and Apparatus for Determining Operational Parameters of Thermoelectric Modules, Journal of Electronic Materials, ISSN: 0361-5235, DOI: 10.1007/s11664-016-4712-1, Vol.45, No.10, pp.5223-5231, 2016
Zybała R., Schmidt M., Kaszyca K., Ciupiński Ł., Kruszewski M.J., Pietrzak K., Method and Apparatus for Determining Operational Parameters of Thermoelectric Modules, Journal of Electronic Materials, ISSN: 0361-5235, DOI: 10.1007/s11664-016-4712-1, Vol.45, No.10, pp.5223-5231, 2016

Abstract:
The main aim of this work was to construct and test an apparatus for characterization of high temperature thermoelectric modules to be used in thermoelectric generator (TEGs) applications. The idea of this apparatus is based on very precise measurements of heat fluxes passing through the thermoelectric (TE) module, at both its hot and cold sides. The electrical properties of the module, under different temperature and load conditions, were used to estimate efficiency of energy conversion based on electrical and thermal energy conservation analysis. The temperature of the cold side, Tc, was stabilized by a precise circulating thermostat (≤0.1°C) in a temperature range from 5°C to 90°C. The amount of heat absorbed by a coolant flowing through the heat sink was measured by the calibrated and certified heat flow meter with an accuracy better than 1%. The temperature of the hot side, Th, was forced to assumed temperature (Tmax = 450°C) by an electric heater with known power (Ph = 0–600 W) with ample thermal insulation. The electrical power was used in calculations. The TE module, heaters and cooling plate were placed in an adiabatic vacuum chamber. The load characteristics of the module were evaluated using an electronically controlled current source as a load. The apparatus may be used to determine the essential parameters of TE modules (open circuit voltage, Uoc, short circuit current, Isc, internal electrical resistance, Rint, thermal resistance, Rth, power density, and efficiency, η, as a function of Tc and Th). Several commercially available TE modules based on Bi2Te3 and Sb2Te3 alloys were tested. The measurements confirmed that the constructed apparatus was highly accurate, stable and yielded reproducible results; therefore, it is a reliable tool for the development of thermoelectric generators.

Keywords:
energy conversion efficiency, power generation, thermoelectric modules, performance characterization, heat recovery, renewable energy

10.Pietrzak K., Sobczak N., Chmielewski M., Homa M., Gazda A., Zybała R., Strojny-Nędza A., Effects of Carbon Allotropic Forms on Microstructure and Thermal Properties of Cu-C Composites Produced by SPS, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-015-1851-0, Vol.25, No.8, pp.3077-3083, 2016
Pietrzak K., Sobczak N., Chmielewski M., Homa M., Gazda A., Zybała R., Strojny-Nędza A., Effects of Carbon Allotropic Forms on Microstructure and Thermal Properties of Cu-C Composites Produced by SPS, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-015-1851-0, Vol.25, No.8, pp.3077-3083, 2016

Abstract:
Combination of extreme service conditions and complex thermomechanical loadings, e.g., in electronics or power industry, requires using advanced materials with unique properties. Dissipation of heat generated during the operation of high-power electronic elements is crucial from the point of view of their efficiency. Good cooling conditions can be guaranteed, for instance, with materials of very high thermal conductivity and low thermal expansion coefficient, and by designing the heat dissipation system in an accurate manner. Conventional materials such as silver, copper, or their alloys, often fail to meet such severe requirements. This paper discusses the results of investigations connected with Cu-C (multiwall carbon nanotubes (MWNTs), graphene nanopowder (GNP), or thermally reduced graphene oxide (RGO)) composites, produced using the spark plasma sintering technique. The obtained composites are characterized by uniform distribution of a carbon phase and high relative density. Compared with pure copper, developed materials are characterized by similar thermal conductivity and much lower values of thermal expansion coefficient. The most promising materials to use as heat dissipation elements seems to be copper-based composites reinforced by carbon nanotubes (CNTs) and GNP.

Keywords:
copper matrix composites, graphene, spark plasma sintering, thermal properties

11.Strojny-Nędza A., Pietrzak K., Węglewski W., The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM), Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-016-2204-3, Vol.25, No.8, pp.3173-3184, 2016
Strojny-Nędza A., Pietrzak K., Węglewski W., The Influence of Al2O3 Powder Morphology on the Properties of Cu-Al2O3 Composites Designed for Functionally Graded Materials (FGM), Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-016-2204-3, Vol.25, No.8, pp.3173-3184, 2016

Abstract:
In order to meet the requirements of an increased efficiency applying to modern devices and in more general terms science and technology, it is necessary to develop new materials. Combining various types of materials (such as metals and ceramics) and developing composite materials seem to be suitable solutions. One of the most interesting materials includes Cu-Al2O3 composite and gradient materials (FGMs). Due to their potential properties, copper-alumina composites could be used in aerospace industry as rocket thrusters and components in aircraft engines. The main challenge posed by copper matrix composites reinforced by aluminum oxide particles is obtaining the uniform structure with no residual porosity (existing within the area of the ceramic phase). In the present paper, Cu-Al2O3 composites (also in a gradient form) with 1, 3, and 5 vol.% of aluminum oxide were fabricated by the hot pressing and spark plasma sintering methods. Two forms of aluminum oxide (αAl2O3 powder and electrocorundum) were used as a reinforcement. Microstructural investigations revealed that near fully dense materials with low porosity and a clear interface between the metal matrix and ceramics were obtained in the case of the SPS method. In this paper, the properties (mechanical, thermal, and tribological) of composite materials were also collected and compared. Technological tests were preceded by finite element method analyses of thermal stresses generated in the gradient structure, and additionally, the role of porosity in the formation process of composite properties was modeled. Based on the said modeling, technological conditions for obtaining FGMs were proposed.

Keywords:
functionally gradient material, shot pressing, metal matrix composites, microstructure, spark plasma sintering, thermal conductivity

12.Chmielewski M., Pietrzak K., Metal-ceramic functionally graded materials – manufacturing, characterization, application, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.1515/bpasts-2016-0017, Vol.64, No.1, pp.151-160, 2016
Chmielewski M., Pietrzak K., Metal-ceramic functionally graded materials – manufacturing, characterization, application, BULLETIN OF THE POLISH ACADEMY OF SCIENCES: TECHNICAL SCIENCES, ISSN: 0239-7528, DOI: 10.1515/bpasts-2016-0017, Vol.64, No.1, pp.151-160, 2016

Abstract:
Functionally graded materials (FGMs) belong to a new, continuously developing group of materials, finding application in various branches of industry. The idea of freely designing their construction profile, restricted only by the available manufacturing techniques, enables obtaining materials with composition and structure gradients having unprecedented properties. In this paper, selected results of works carried out by the authors and relating to the application of the developed metal-ceramic composites were presented in order to manufacture functionally graded materials for target purposes. Gradient structures with various construction profiles that can play different roles were produced on the basis on the following material pairs: Cr-Al2O3, NiAl-Al2O3 and Cu-AlN. Manufacturing conditions, microstructure characteristics and selected properties, crucial from the point of view of future applications, were presented.

Keywords:
metal-ceramic functionally graded materials, manufacturing, characterization, application

13.Jurczak K., Rojek J., Nosewicz S., Lumelskyy D., Bochenek K., Chmielewski M., Pietrzak K., Modelowanie wstępnego prasowania proszków metodą elementów dyskretnych, HUTNIK - WIADOMOŚCI HUTNICZE, ISSN: 1230-3534, DOI: 10.15199/24.2016.1.1, Vol.83, No.1, pp.3-7, 2016
Jurczak K., Rojek J., Nosewicz S., Lumelskyy D., Bochenek K., Chmielewski M., Pietrzak K., Modelowanie wstępnego prasowania proszków metodą elementów dyskretnych, HUTNIK - WIADOMOŚCI HUTNICZE, ISSN: 1230-3534, DOI: 10.15199/24.2016.1.1, Vol.83, No.1, pp.3-7, 2016

Abstract:
W niniejszym artykule zaprezentowano wyniki modelowania zagęszczania proszku stanowiącego wstępny etap procesu prasowania na gorąco. Modelowanie numeryczne zrealizowano metodą elementów dyskretnych z wykorzystaniem kulistych cząstek. Analizę skoncentrowano na badaniu mechanizmów zagęszczania proszku przy ciśnieniu do 50 MPa oraz poszukiwaniu modeli odpowiednich przy zastosowanych warunkach realizacji procesu. Symulacje numeryczne wykonano wykorzystując dwa modele oddziaływania cząstek proszku: sprężysty model Hertza-Mindlina-Deresiewicza oraz plastyczny model Storåkersa. Wyniki numeryczne zostały porównane z wynikami laboratoryjnymi prasowania proszku NiAl. Otrzymano dużą zgodność wyników eksperymentalnych i numerycznych.

This paper presents the results of discrete element simulation of powder compaction which is the initial stage in the hot pressing process. Numerical simulation has been performed by discrete element method with using spherical particles. The research has been focused on densification mechanisms under pressure 50 MPa and models appropriate for these conditions. Numerical simulations have been carried out for two contact models: elastic Hertz-Mindlin-Deresiewicz and plastic - Storåkers. Numerical results and results from laboratory test of the uniaxial pressing of NiAl powder have been compared. The obtained results of numerical simulation and laboratory tests showing a good agreement.

Keywords:
metoda elementów dyskretnych, prasowanie proszków, materiały intermetaliczne, discrete element method, powder compaction, intermetallics

14.Rojek J., Nosewicz S., Jurczak K., Chmielewski M., Bochenek K., Pietrzak K., Discrete element simulation of powder compaction in cold uniaxial pressing with low pressure, Computational Particle Mechanics, ISSN: 2196-4378, DOI: 10.1007/s40571-015-0093-0, Vol.3, pp.513-524, 2016
Rojek J., Nosewicz S., Jurczak K., Chmielewski M., Bochenek K., Pietrzak K., Discrete element simulation of powder compaction in cold uniaxial pressing with low pressure, Computational Particle Mechanics, ISSN: 2196-4378, DOI: 10.1007/s40571-015-0093-0, Vol.3, pp.513-524, 2016

Abstract:
This paper presents numerical studies of powder compaction in cold uniaxial pressing. The powder compaction in this work is considered as an initial stage of a hot pressing process so it is realized with relatively low pressure (up to 50 MPa). Hence the attention has been focused on the densification mechanisms at this range of pressure and models suitable for these conditions. The discrete element method employing spherical particles has been used in the numerical studies. Numerical simulations have been performed for two different contact models—the elastic Hertz–Mindlin–Deresiewicz model and the plastic Storåkers model. Numerical results have been compared with the results of laboratory tests of the die compaction of the NiAl powder. Comparisons have shown that the discrete element method is capable to represent properly the densification mechanisms by the particle rearrangement and particle deformation.

Keywords:
Discrete element method, Simulation, Powder compaction, Cold uniaxial pressing

15.Strojny-Nędza A., Pietrzak K., Węglewski W., The Influence of Electrocorundum Granulation on the Properties of Sintered Cu/Electrocorundum Composites, SCIENCE OF SINTERING, ISSN: 0350-820X, DOI: 10.2298/SOS1503249S, Vol.47, pp.249-258, 2015
Strojny-Nędza A., Pietrzak K., Węglewski W., The Influence of Electrocorundum Granulation on the Properties of Sintered Cu/Electrocorundum Composites, SCIENCE OF SINTERING, ISSN: 0350-820X, DOI: 10.2298/SOS1503249S, Vol.47, pp.249-258, 2015

Abstract:
Copper/alumina composites are extensively used in automotive and aerospace industry for products that are subjected to severe thermal and mechanical loadings, such as rocket thrusters and components of aircraft engines. These materials are well-known for their good frictional wear resistance, good resistance to thermal fatigue, high thermal conductivity and high specific heat. In this paper, the sintering process of copper/electrocorundum composites reinforced by electrocorundum particles with diameters of 3 or 180 μm and 1, 3, 5 vol.% content is presented. The effects of different particle sizes of the ceramic reinforcement on the microstructure, physical, mechanical, tribological and thermal properties of the fabricated composites are discussed.

Keywords:
copper/alumina composites, sintering, modeling of thermal properties, microstructure, mechanical properties

16.Chmielewski M., Nosewicz S., Rojek J., Pietrzak K., Mackiewicz S., Romelczyk B., A study of densification and microstructure evolution during hot pressing of NiAl/Al2O3 composite, Advanced Composite Materials, ISSN: 0924-3046, DOI: 10.1080/09243046.2013.879408, Vol.24, No.1, pp.57-66, 2015
Chmielewski M., Nosewicz S., Rojek J., Pietrzak K., Mackiewicz S., Romelczyk B., A study of densification and microstructure evolution during hot pressing of NiAl/Al2O3 composite, Advanced Composite Materials, ISSN: 0924-3046, DOI: 10.1080/09243046.2013.879408, Vol.24, No.1, pp.57-66, 2015

Abstract:
Evolution of the density and the microstructure during hot pressing of NiAl/Al2O3 composite has been investigated in the present paper. In particular, the effect of the process parameters, viz. compacting pressure, sintering temperature and sintering time, on the evolution of the density of the intermetallic–ceramic composite has been studied. Evolution of the density has been related to microstructure changing. Porosity, pore structures and grains rearrangement have been analysed in microscopic observations.

Keywords:
hot pressing, sintering, intermetallic–ceramic composite, density evolution, microstructure

17.Rojek J., Nosewicz S., Pietrzak K., Chmielewski M., Evaluation of macroscopic stresses in discrete element models of sintering processes, COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.15, No.1, pp.219-255, 2015
Rojek J., Nosewicz S., Pietrzak K., Chmielewski M., Evaluation of macroscopic stresses in discrete element models of sintering processes, COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.15, No.1, pp.219-255, 2015

Abstract:
This paper presents investigation of macroscopic stresses in powder metallurgy process modelled with the discrete element method. The discrete element model belongs to the class of micromechanical models. In the DEM model the material is represented by an assembly of particles interacting by contact forces and the method is formulated in terms of forces and displacements. In order to evaluate macroscopic stresses a special upscaling procedure is necessary. The paper presents basic formulation of the discrete element method with special attention for the contact interaction models for powder compaction and sintering. A method to evaluate macroscopic stresses based on the two level averaging is presented. The discrete element model of sintering is verified using own experimental results. Macroscopic stresses are calculated for the whole process including loading, heating, sintering, cooling and unloading. It has been found out that the macroscopic stresses are consistent with changing process parameters. The procedure is suitable for multiscale modelling of sintering.

Keywords:
sintering, modeling, discrete element method, macroscopic stresses

18.Węglewski W., Basista M., Manescu A., Chmielewski M., Pietrzak K., Schubert Th., Effect of grain size on thermal residual stresses and damage in sintered chromium–alumina composites: Measurement and modeling, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2014.06.027, Vol.67, pp.119-124, 2014
Węglewski W., Basista M., Manescu A., Chmielewski M., Pietrzak K., Schubert Th., Effect of grain size on thermal residual stresses and damage in sintered chromium–alumina composites: Measurement and modeling, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2014.06.027, Vol.67, pp.119-124, 2014

Abstract:
In this paper we present the results of experimental measurements and numerical modeling of the effect of particle size on the residual thermal stresses arising in sintered metal–matrix composites after cooling down from the fabrication temperature. On example of novel Cr(Re)/Al2O3 composites processed by (i) spark plasma sintering and (ii) hot pressing the residual thermal stresses are measured by neutron diffraction technique and determined by a FEM model based on micro-CT scans of the material microstructure. Then numerical model of microcracking induced by residual stresses is applied to predict the effective Young modulus of the damaged composite. Comparison of the numerical results with the measured data of the residual stresses and Young’s modulus is presented and fairly good agreement is noted.

Keywords:
Metal–matrix composites (MMC), Residual/internal stress, Finite element analysis (FEA), Sintering

19.Nosewicz S., Rojek J., Mackiewicz S., Chmielewski M., Pietrzak K., Romelczyk B., The influence of hot pressing conditions on mechanical properties of nickel aluminide/alumina composite, Journal of Composite Materials, ISSN: 0021-9983, DOI: 10.1177/0021998313511652, Vol.48, No.29, pp.3577-3589, 2014
Nosewicz S., Rojek J., Mackiewicz S., Chmielewski M., Pietrzak K., Romelczyk B., The influence of hot pressing conditions on mechanical properties of nickel aluminide/alumina composite, Journal of Composite Materials, ISSN: 0021-9983, DOI: 10.1177/0021998313511652, Vol.48, No.29, pp.3577-3589, 2014

Abstract:
The influence of hot pressing conditions on mechanical properties of nickel aluminide/alumina composite has been investigated in the present paper. In particular, effect of the process parameters, viz. compacting pressure, sintering temperature and sintering time on the evolution of density, elastic constants and tensile strength properties of the intermetallic-ceramic composite has been studied. Elastic constants, the Young's modulus and Poisson's ratio, have been evaluated using an ultrasonic testing method, and the tensile strength has been determined by a Brazilian-type splitting test. Microscopic observations of microstructure evolution complemented the experimental procedure. Experimental results have been confronted with theoretical models showing a good agreement between the data compared.

Keywords:
Hot pressing, sintering, intermetallic-ceramic composite, elastic properties, Brazilian test, tensile strength, ultrasonic method

20.Chmielewski M., Pietrzak K., Strojny-Nędza A., Dubiel B., Czyrska-Filemonowicz A., Effect of rhenium addition on the strengthening of chromium-alumina composite materials, INTERNATIONAL JOURNAL OF MATERIALS RESEARCH, ISSN: 1862-5282, DOI: 10.3139/146.111002, Vol.105, No.2, pp.200-207, 2014
Chmielewski M., Pietrzak K., Strojny-Nędza A., Dubiel B., Czyrska-Filemonowicz A., Effect of rhenium addition on the strengthening of chromium-alumina composite materials, INTERNATIONAL JOURNAL OF MATERIALS RESEARCH, ISSN: 1862-5282, DOI: 10.3139/146.111002, Vol.105, No.2, pp.200-207, 2014

Abstract:
Chromium–alumina composites are well known for their good mechanical properties in comparison to pure ceramics or metals. These composites are characterized by high hardness and high mechanical strength. The aim of the present work was to improve the properties of chromium–alumina composites even more and expand the range of their possible applications by addition of rhenium. To achieve this goal, chromium–alumina composites containing 2 and 5 vol.% of rhenium were produced via powder metallurgy. The microstructural characterization of the processed material was performed using light microscopy, scanning and transmission electron microscopy as well as X-ray diffraction analysis. Measurement of selected properties such as Young's modulus, bend strength and hardness revealed an advantageous influence of rhenium additions. The results are discussed in terms of the influence of rhenium volume content on the microstructure and on the physical and mechanical properties of the chromium–alumina composites. The solid solution is only partially formed. The properties strongly depend on the amount and distribution of both aluminium oxide and rhenium content.

21.Chmielewski M., Nosewicz S., Pietrzak K., Rojek J., Strojny-Nędza A., Mackiewicz S., Dutkiewicz J., Sintering Behavior and Mechanical Properties of NiAl, Al2O3, and NiAl-Al2O3 Composites, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-014-1189-z, Vol.23, No.11, pp.3875-3886, 2014
Chmielewski M., Nosewicz S., Pietrzak K., Rojek J., Strojny-Nędza A., Mackiewicz S., Dutkiewicz J., Sintering Behavior and Mechanical Properties of NiAl, Al2O3, and NiAl-Al2O3 Composites, Journal of Materials Engineering and Performance, ISSN: 1059-9495, DOI: 10.1007/s11665-014-1189-z, Vol.23, No.11, pp.3875-3886, 2014

Abstract:
It is commonly known that the properties of sintered materials are strongly related to technological conditions of the densification process. This paper shows the sintering behavior of a NiAl-Al2O3 composite, and its individual components sintered separately. Each kind of material was processed via the powder metallurgy route (hot pressing). The progress of sintering at different stages of the process was tested. Changes in the microstructure were examined using scanning and transmission electron microscopy. Metal-ceramics interface was clean and no additional phases were detected. Correlation between the microstructure, density, and mechanical properties of the sintered materials was analyzed. The values of elastic constants of NiAl/Al2O3 were close to intermetallic ones due to the volume content of the NiAl phase particularly at low densities, where small alumina particles had no impact on the composite’s stiffness. The influence of the external pressure of 30 MPa seemed crucial for obtaining satisfactory stiffness for three kinds of the studied materials which were characterized by a high dense microstructure with a low number of isolated spherical pores.

Keywords:
ceramics, composites, electron, intermetallic, metallic matrix, microscopy, powder metallurgy, sintering, structural

22.Jach K., Pietrzak K., Wajler A., Strojny-Nędza A., Fabrication of an alumina-copper composite using a ceramic preform, Powder Metallurgy and Metal Ceramics, ISSN: 1068-1302, DOI: 10.1007/s11106-014-9577-3, Vol.52, No.11-12, pp.680-685, 2014
Jach K., Pietrzak K., Wajler A., Strojny-Nędza A., Fabrication of an alumina-copper composite using a ceramic preform, Powder Metallurgy and Metal Ceramics, ISSN: 1068-1302, DOI: 10.1007/s11106-014-9577-3, Vol.52, No.11-12, pp.680-685, 2014

Abstract:
In this work alumina preforms with an open porosity of 85 and 90% were produced by the replication method. The obtained preforms were used for the fabrication of Cu–Al2O3 composites. We analyzed the effect of applying pressure during a hot-pressing process on the microstructure and mechanical and thermal properties of the obtained materials. It was found that application of higher pressure (10 MPa) during sintering led to the destruction of the ceramic preforms. It facilitated filling of the remaining pores with copper, which resulted in a more homogeneous material with better mechanical and thermal properties.

Keywords:
Cu–Al2O3 composites, hot-pressing process, ceramic reforms, microstructure, mechanical properties

23.Nosewicz S., Rojek J., Pietrzak K., Chmielewski M., Viscoelastic discrete element model of powder sintering, POWDER TECHNOLOGY, ISSN: 0032-5910, DOI: 10.1016/j.powtec.2013.05.020, Vol.246, pp.157-168, 2013
Nosewicz S., Rojek J., Pietrzak K., Chmielewski M., Viscoelastic discrete element model of powder sintering, POWDER TECHNOLOGY, ISSN: 0032-5910, DOI: 10.1016/j.powtec.2013.05.020, Vol.246, pp.157-168, 2013

Abstract:
This paper presents an original viscoelastic model of powder sintering developed within the discrete element framework. The viscous model used by other authors has been enriched by adding a spring connected in series to the viscous rheological element. In this way elastic and viscous effects in the particle interaction during sintering are treated using the Maxwell viscoelasticity. The new numerical model has been verified through simulation of simple problems of free sintering and sintering under pressure. Sintering processes have been treated as isothermic. In order to accelerate the analysis an algorithmic mass scaling has been used allowing to use larger time steps in the explicit time integration scheme. The results obtained using the new model are consistent with the standard viscous model. At the same time, a much better efficiency of the new model in comparison to the standard viscous one has been found because the critical time steps required by the viscoelastic model are much larger than those required by the viscous model. The new model has been applied to the simulation of real process of sintering of NiAl powder. The kinetics of sintering indicated by the evolution of density has been studied. The comparison of numerical and experimental results has shown a good performance of the developed numerical model.

Keywords:
Powder sintering, Simulation, Discrete element method, Viscoelastic model

24.Jach K., Pietrzak K., Wajler A., Sidorowicz A., Brykała U., Application of ceramic preforms to the manufacturing of ceramic - metal composites, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/amm-2013-0188, Vol.58, No.4, pp.1425-1428, 2013
Jach K., Pietrzak K., Wajler A., Sidorowicz A., Brykała U., Application of ceramic preforms to the manufacturing of ceramic - metal composites, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/amm-2013-0188, Vol.58, No.4, pp.1425-1428, 2013

Abstract:
This paper presents new solution to manufacturing Cu-Al2O3 composites with a dispersed reinforcement phase. It consists in substituting commonly used commercial alumina powder with crushed ceramic foam. Very low strength of thin-walled Al2O3 porous foams results in both their easy destruction and isolation of fragments <200 μm. The addition of the ceramic phase is 3-10 vol.%. The sintering process is performed for 30 min in a hot-press at 1050°C and 30 MPa. The aim of the presented paper is to study the effect of the volume content of the ceramic phase on the microstructure and selected physical and thermal properties of copper - alumina composites.

Keywords:
ceramic preform, composite, copper, sintering

25.Basista M., Pietrzak K., Węglewski W., Chmielewski M., Kompozyty spiekane Cr-Al2O3 z dodatkiem renu. Wytwarzanie, właściwości, modelowanie, zastosowania, RUDY I METALE NIEŻELAZNE, ISSN: 0035-9696, Vol.R58, No.10, pp.556-563, 2013
Basista M., Pietrzak K., Węglewski W., Chmielewski M., Kompozyty spiekane Cr-Al2O3 z dodatkiem renu. Wytwarzanie, właściwości, modelowanie, zastosowania, RUDY I METALE NIEŻELAZNE, ISSN: 0035-9696, Vol.R58, No.10, pp.556-563, 2013

Abstract:
Celem pracy było zbadanie wpływu dodatku renu na właściwości termomechaniczne i użytkowe kompozytów Cr-Al2O3 wytwarzanych metodą spiekania pod ciśnieniem w prasie HP oraz metodą Spark Plasma Sintering (SPS). Uzyskano kompozyty o gęstości przekraczającej 98% gęstości teoretycznej. Właściwości mechaniczne (m.in. moduł Younga, wytrzymałość na zginanie, twardość, odporność na pękanie, granica plastycznośći) oraz odporność na utlenianie wytworzonych materiałów są obiecujące. Zbudowano model numeryczny do obliczeń wielkości naprężeń resztkowych obecnych w materiałach faz kompozytu po procesie spiekania oraz modułów sprężystości. Wykorzystano w tym celu obrazy rzeczywistej mikrostruktury kompozytu otrzymane z tomografii komputerowej. Uzyskano dobrą zgodność wyników modelu z wynikami pomiarów naprężeń metodą XRD. Przedstawiono ponadto porównanie wyników obliczeń numerycznych i pomiarów modułu Younga przy zastosowaniu różnych metod

Keywords:
kompozyty MMC, metalurgia proszków, modelowanie MES, mikrotomografia komputerowa, naprężenia resztkowe

26.Rojek J., Nosewicz S., Pietrzak K., Chmielewski M., Simulation of Powder Sintering Using a Discrete Element Model, ACTA MECHANICA ET AUTOMATICA, ISSN: 1898-4088, DOI: 10.2478/ama-2013-0030, Vol.7, pp.175-179, 2013
Rojek J., Nosewicz S., Pietrzak K., Chmielewski M., Simulation of Powder Sintering Using a Discrete Element Model, ACTA MECHANICA ET AUTOMATICA, ISSN: 1898-4088, DOI: 10.2478/ama-2013-0030, Vol.7, pp.175-179, 2013

Abstract:
This paper presents numerical simulation of powder sintering. The numerical model introduced in this work employs the discrete element method which assumes that material can be modelled by a large assembly of discrete elements (particles) of spherical shape interacting among one another. Modelling of sintering requires introduction of the cohesive interaction among particles representing interparticle sintering forces. Numerical studies of sintering have been combined with experimental studies which provided data for calibration and validation of the model. In the laboratory tests evolution of microstructure and density during sintering have been studied. Comparison of numerical and experimental results shows a good performance of the numerical model developed

Keywords:
Powder Sintering, Simulation, Discrete Element Method

27.Węglewski W., Basista M., Chmielewski M., Pietrzak K., Modeling of thermally induced damage in the processing of Cr–Al2O3 composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2011.07.016, Vol.43B, No.2, pp.255-264, 2012
Węglewski W., Basista M., Chmielewski M., Pietrzak K., Modeling of thermally induced damage in the processing of Cr–Al2O3 composites, COMPOSITES PART B-ENGINEERING, ISSN: 1359-8368, DOI: 10.1016/j.compositesb.2011.07.016, Vol.43B, No.2, pp.255-264, 2012

Abstract:
Thermal stresses induced during the cooling of Cr–Al2O3 (MMC) processed by sintering are modeled numerically using the FEA. The composite microstructure is modeled as (i) random distribution of ceramic particles (voxels) in the metal matrix, and (ii) using micro-CT scans of the real microstructure transformed into a FE mesh. Numerical simulations of the thermal residual stresses are compared with the test data measured by X-ray diffraction. A simple numerical model is then proposed to predict the overall elastic properties of the composite with account of the porosity and damage induced by the thermal stresses. Comparison of the model predictions with the measured data for Young’s modulus is presented.

Keywords:
Metal-matrix composites (MMCs), Residual/internal stress, Finite element analysis (FEA), Sintering

28.Nosewicz Sz., Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Modelowanie procesu spiekania materiałów dwufazowych metodą elementów dyskretnych, RUDY I METALE NIEŻELAZNE, ISSN: 0035-9696, Vol.57, No.9, pp.599-603, 2012
Nosewicz Sz., Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Modelowanie procesu spiekania materiałów dwufazowych metodą elementów dyskretnych, RUDY I METALE NIEŻELAZNE, ISSN: 0035-9696, Vol.57, No.9, pp.599-603, 2012

Abstract:
W niniejszym artykule zostały przedstawione nowe wyniki modelowania procesu spiekania metodą elementów dyskretnych. W sformułowaniu teoretycznym dla części sprężystej zastosowano model kontaktu Hertza w celu lepszego odwzorowania oddziaływania elementów kulistych w trakcie prasowania. Sformułowanie i implementację modelu rozszerzono na przypadek spiekania materiałów dwufazowych. Na podstawie badań literaturowych wyznaczono parametry materiałowe procesu, które zostały następnie zweryfikowane za pomocą wyników eksperymentalnych. Wyniki numeryczne ewolucji gęstości próbki porównano z wynikami doświadczalnymi otrzymując dużą zgodność.

Keywords:
materiały dwufazowe, metalurgia proszków, spiekanie, metoda elementów dyskretnych

29.Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Nosewicz S., Discrete Element Simulation of Powder Sintering, COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.11, No.1, pp.68-73, 2011
Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Nosewicz S., Discrete Element Simulation of Powder Sintering, COMPUTER METHODS IN MATERIALS SCIENCE / INFORMATYKA W TECHNOLOGII MATERIAŁÓW, ISSN: 1641-8581, Vol.11, No.1, pp.68-73, 2011

Abstract:
This paper presents numerical modelling of powder sintering. The numerical model introduced in this work employs the discrete element method which assumes that material can be modelled by a large assembly of discrete elements (particles) of spherical shape interacting among one another. Modelling of sintering requires introduction of the cohesive interaction among particles representing inter-particle sintering forces. Numerical studies of sintering have been supplemented with experimental studies which provided data for calibration and validation of the model. In the laboratory tests evolution of microstructure and density during sintering have been studied. Comparison of numerical and experimental results shows a good performance of the numerical model developed.

Keywords:
powder sintering, powder metallurgy, simulation, discrete element method

30.Węglewski W., Chmielewski M., Kaliński D., Pietrzak K., Basista M., Thermal residual stresses generated during processing of Cr/Al2O3 composites and their influence on macroscopic elastic properties, Advances in Science and Technology, ISSN: 1662-0356, DOI: 10.4028/www.scientific.net/AST.65.27, Vol.65, pp.27-32, 2010
Węglewski W., Chmielewski M., Kaliński D., Pietrzak K., Basista M., Thermal residual stresses generated during processing of Cr/Al2O3 composites and their influence on macroscopic elastic properties, Advances in Science and Technology, ISSN: 1662-0356, DOI: 10.4028/www.scientific.net/AST.65.27, Vol.65, pp.27-32, 2010

Abstract:
This work is focused on the modeling of thermal stresses induced during the fabrication of the metal/ceramic composites. On example of Cr-Al2O3 composite processed by powder metallurgy, thermal stresses after fabrication are determined by FEM model for different contents of metal and ceramic phases. Numerical model of microcracking induced by thermal stresses is then proposed and applied to compute the overall elastic properties of the damaged composite. Comparison of the model predictions with the measur ed data for Young's modulus is presented.

Keywords:
Cr-Al2O3 composite, mechanical properties, thermal stress modeling, microcracking, Young’s modulus modeling

31.Chmielewski M., Pietrzak K., Kaliński D., Strojny A., Processing and thermal properties of Cu-AlN composites, Advances in Science and Technology, ISSN: 1662-0356, DOI: 10.4028/www.scientific.net/AST.65.100, Vol.65, pp.100-105, 2010
Chmielewski M., Pietrzak K., Kaliński D., Strojny A., Processing and thermal properties of Cu-AlN composites, Advances in Science and Technology, ISSN: 1662-0356, DOI: 10.4028/www.scientific.net/AST.65.100, Vol.65, pp.100-105, 2010

Abstract:
Heat transfer by conduction is involved in the use of heat sinks dissipitating heat from electronic devices. Effective transfer of heat requires using materials of high thermal conductivity. In addition, it requires appropriate values of thermal expansion, matched to the semiconductor materials, high purity of materials used and good contact between bonded elements across which heat transfer occurs. The conventional materials are not able to fulfil still raising and complex requirements. The solutions of this problem could be using the composites materials, where the combinations of different properties is possible to use. This study presents the technological tests and the analysis of correlation between processing parameters and the properties of copperaluminium nitride composites. Composite materials were obtained by mixing in planetary ball mill and then densified using the sintering under pressure or hot pressing method. The microstructure of obtained composite materials using optical microscopy and scanning electron microscopy were analyzed. Coefficient of thermal expansion (CTE) and thermal conductivity (TC) were investigated depending on the process conditions

Keywords:
Composite Material, Hot-Pressing, Sintering, Thermal Conductivity (TC), Thermal Diffusivity, Thermal Expansion Coefficient


Conference papers
1.Pietrzak K., Kaliński D., Chmielewski M., Chmielewski T., Włosiński W., Choręgiewicz K., Processing of intermetallics with Al2O3 or steel joints obtained by friction welding technique, ECerS XII, 12th Conference of the European Ceramic Society, 2011-06-19/06-23, Stockholm (SE), pp.1-4, 2011
Pietrzak K., Kaliński D., Chmielewski M., Chmielewski T., Włosiński W., Choręgiewicz K., Processing of intermetallics with Al2O3 or steel joints obtained by friction welding technique, ECerS XII, 12th Conference of the European Ceramic Society, 2011-06-19/06-23, Stockholm (SE), pp.1-4, 2011

Abstract:
The development of technologies for joining advanced materials is connected with an introduction of new materials and new applications of their bonds, to work in ever more difficult conditions. One of possibilities of obtaining this type of joints is using the friction welding technique. This paper presents the results of joining intermetallics (Fe-Al and Ni-Al type) with steel (S235JR) and ceramics (Al2O3) using friction welding technique. The focus of the investigations was selecting: appropriate rotational speed (10000-25000rpm) of joining elements, welding pressure and time (1500-4500ms) of its application and swelling time (1000-7000ms). The paper presents the results of microstructure investigations, investigations of microhardness (perpendicularly to joint surface) and mechanical properties (tensile strength).

Keywords:
friction welding, intermetallics, microstructure of joints, microhardness, tensile strength

2.Pietrzak K., Jach K., Kaliński D., Chmielewski M., Morgiel J., Processing and Microstructure of Al2O3-Cu Composite Material Interpenetrating Network Type, Euro PM2011 Congress and Exhibition, 2011-10-09/10-12, Barcelona (ES), Vol.2, pp.1-6, 2011
Pietrzak K., Jach K., Kaliński D., Chmielewski M., Morgiel J., Processing and Microstructure of Al2O3-Cu Composite Material Interpenetrating Network Type, Euro PM2011 Congress and Exhibition, 2011-10-09/10-12, Barcelona (ES), Vol.2, pp.1-6, 2011

Abstract:
Alumina/copper composites have been used where high thermal conductivity, high absorption and dissipation of heat, high resistance to thermal fatigue and good frictional wear resistance are required. This kind of composites may be applied in medicine, electronic and automotive industry. Both the physical and mechanical properties of this type of composites are strongly influenced by the properties of its individual constituents and, also, by the properties of interface layer between ceramic and metal. One of the solution, from the point of view of the best properties’ achievements (especially thermal, structural and shape stability), is the production of ceramic-metal composites with interpenetrating networks structure. They can be produced using porous alumina performs, which are infiltrated (pressure or pressureless) by molten metal or sintered with metallic powders. The subject of the presented paper is the development of the interpenetrating network Al2O3-Cu composites, processed by sintering porous ceramic perform (85 and 90% porosity) with copper powder. The paper presents the new developed technology, results of microstructure investigations, measurements of the selected physical and mechanical properties and the analysis of the influence of the processing conditions on the properties and interface morphology between ceramic and copper

3.Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Modelowanie spiekania proszków metalicznych metodą elementów dyskretnych, KomPlasTech 2010, XVII Konferencja Informatyka w Technologii Metali, 2010-01-10/01-13, Białka Tatrzańska (PL), pp.1-8, 2010
Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Modelowanie spiekania proszków metalicznych metodą elementów dyskretnych, KomPlasTech 2010, XVII Konferencja Informatyka w Technologii Metali, 2010-01-10/01-13, Białka Tatrzańska (PL), pp.1-8, 2010

Abstract:
W artykule przedstawiono badania doświadczalne oraz modelowanie numeryczne procesu spiekania proszków metalicznych. W części eksperymentalnej pracy badano ewolucję mikrostruktury oraz gęstości spieku w trakcie procesu spiekania. Jako metodę modelowania wybrano metodę elementów dyskretnych, w której zakłada się, że materiał jest reprezentowany przez liczny zbiór elementów dyskretnych (cząstek) o kształcie sferycznym oddziałujących między sobą. Modelowanie spiekania wymaga wprowadzenia oddziaływania kohezyjnego między cząstkami reprezentującego naprężenia powstające między ziarnami w trakcie spiekania. W artykule przedstawiono wstępne wyniki numeryczne pokazujące ewolucję naprężenia w trakcie spiekania między dwoma ziarnami spiekanego proszku.

Keywords:
spiekanie, metalurgia proszków, związki międzymetaliczne, modelowanie, metoda elementów dyskretnych

4.Pietrzak K., Jach K., Kaliński D., Chmielewski M., Improving alumina wettabillity by modification of copper alloys chemical composition, PM2010, Powder Metallurgy World Congress and Exhibition, 2010-10-10/10-14, Florence (IT), Vol.2, pp.361-367, 2010

Conference abstracts
1.Nosewicz S., Jurczak K., Rojek J., Chmielewski M., Pietrzak K., Application of contact interaction of Hertz model to viscoelastic discrete element model of sintering, ISNNM, 14th International Symposium on Novel and Nano Materials, 2016-07-03/07-08, Budapeszt (HU), pp.119, 2016
2.Jurczak K., Rojek J., Nosewicz S., Lumelskyy D., Bochenek K., Chmielewski M., Pietrzak K., Modelowanie wstępnego prasowania proszków metodą elementów dyskretnych, KomPlasTech 2016, XXIII Konferencja Informatyka w Technologii Metali, 2016-01-17/01-20, Wisła (PL), pp.68, 2016
Jurczak K., Rojek J., Nosewicz S., Lumelskyy D., Bochenek K., Chmielewski M., Pietrzak K., Modelowanie wstępnego prasowania proszków metodą elementów dyskretnych, KomPlasTech 2016, XXIII Konferencja Informatyka w Technologii Metali, 2016-01-17/01-20, Wisła (PL), pp.68, 2016

Abstract:
W niniejszym artykule zaprezentowano wyniki modelowania, zagęszczania proszku stanowiącego wstępny etap procesu prasowania na gorąco, metodą elementów dyskretnych opisaną w [1]. Modelowanie numeryczne zrealizowano metodą elementów dyskretnych, z wykorzystaniem kulistych cząstek. Badania skoncentrowano na mechanizmach zagęszczania proszku przy ciśnieniu 50 MPa oraz modelach odpowiednich przy zastosowanych warunkach procesu. Numeryczne symulacje wykonano z wykorzystaniem dwóch modeli: pierwszy - elastyczny Hertz-Mindlin-Deresiewicz, drugi - plastyczny Storakers, opisanych w pracy [2]. Wyniki symulacji numerycznych zostały porównane z wynikami laboratoryjnymi zagęszczania proszku NiAl w matrycy. W rezultacie otrzymano dużą zgodność wyników eksperymentalnych i numerycznych.

Keywords:
metoda elementów dyskretnych, modelowanie, zagęszczanie proszków, prasowanie

3.Nosewicz S., Rojek J., Pietrzak K., Chmielewski M., Discrete element modelling of hot pressing process, EUROMAT 2015, European Congress and Exhibition on Advanced Materials and Processes, 2015-09-20/09-24, Warszawa (PL), pp.1, 2015
4.Basista M., Węglewski W., Bochenek K., Chmielewski M., Pietrzak K., Chromium-rhenium-alumina composites for powertrain application: Processing route, microstructure, properties and numerical modelling, EUROMAT 2015, European Congress and Exhibition on Advanced Materials and Processes, 2015-09-20/09-24, Warszawa (PL), pp.1, 2015
Basista M., Węglewski W., Bochenek K., Chmielewski M., Pietrzak K., Chromium-rhenium-alumina composites for powertrain application: Processing route, microstructure, properties and numerical modelling, EUROMAT 2015, European Congress and Exhibition on Advanced Materials and Processes, 2015-09-20/09-24, Warszawa (PL), pp.1, 2015

Abstract:
Chromium based composites reinforced with alumina particles combineenhanced thermal, oxidation and wear resistance with mechanical strength and hardness. Because of these valuable properties Cr/Al2O3 composites can be used e.g. in the automotive sector for elements of powertrain. Rhenium due to its good mechanical and thermal properties is primarily used as an admixture of nickel superalloys in the aerospace and chemical industries. In the present paper a powder metallurgy route was used to manufacture dense Cr/Re/Al2O3 bulk composites with rhenium admixture of 2vol% and 5vol%. Composites were processed by hot pressing (HP) and by spark plasma sintering (SPS) techniques. The density of the sintered composites exceeded 98% of the theoretical value. Microstructural characterisation revealed that a solid solution of rhenium in chromium was partially formed. Mechanical properties such as Young’s modulus, bending strength, hardness, plastic limit are promising so are oxidation and corrosion resistance. A numerical FE model was developed for the prediction of thermal residual stresses (TRS) and damage generated in the metal and ceramic phase during cooling from high sintering temperature down to room temperature. The model uses micro-CTimages of the real material microstructure as the input data. A good agreement of the simulation results for TRS and the measurements of by neutron diffraction was achieved. The obtained Cr/Re/Al2O3composites were already tested as demonstrators of valve seats in combustion engines and good preliminary results were reported.

Keywords:
Chromium-alumina MMC, rhenium admixture, powder metallurgy, thermal residual stresses, microCT FEM

5.Strojny-Nędza A., Pietrzak K., Jarząbek D.M., Gładki A., Correlation between preparing conditions, starting materials morphology and the interface structure of the Cu-Al2O3 composites, EUROMAT 2015, European Congress and Exhibition on Advanced Materials and Processes, 2015-09-20/09-24, Warszawa (PL), pp.1, 2015
Strojny-Nędza A., Pietrzak K., Jarząbek D.M., Gładki A., Correlation between preparing conditions, starting materials morphology and the interface structure of the Cu-Al2O3 composites, EUROMAT 2015, European Congress and Exhibition on Advanced Materials and Processes, 2015-09-20/09-24, Warszawa (PL), pp.1, 2015

Abstract:
Copper/alumina composites with different volume content are used where high thermal conductivity, high absorption and dissipation of heat, high resistance to thermal fatigue and good frictional wear resistance are required. The properties of these composites depend on the content, shape and distribution of the ceramic phase in metal matrix. All these conditions have influence on said properties and, in consequence, on the future applications of the final material. In the technology of thruster and components in aircraft engines composite materials powder preparation process becomes very important. It should assure the uniform distribution of reinforcement in the matrix and eliminate of any agglomerates which cause the formation o f porosity in the final product . The aim of this paper is elaboration of the mechanical alloying conditions for composite powder consists of copper as a plastic matrix and brittle aluminium oxides as a reinforcement phase. The materials by compositions Cu - 5 vol. %Al 2 O 3 and Cu -15 vol. %Al 2 O 3 were obtained by hot pressing technique. The research methodology includes a microstructure analysis of composites structures, its con nection with the strength of Cu/ Al 2 O 3 interfaces . The results also were analyzed and discussed in terms of the effects of different form of aluminium oxide powder (α -Al 2 O 3 and electrocorundum ) on the composites properties

6.Nosewicz S., Rojek J., Pietrzak K., Chmielewski M., Numerical modeling of stresses in composites manufactured by powder metallurgy, ICMM3, 3rd International Conference on Material Modelling incorporating 13th European Mechanics of Materials Conference, 2013-09-08/09-11, Warszawa (PL), pp.133, 2013
7.Rojek J., Nosewicz S., Pietrzak K., Chmielewski M., Discrete element modelling of powder metallurgy processes, Particles 2013, III International Conference on Particle-based Methods, 2013-09-18/09-20, Stuttgart (DE), pp.1, 2013
8.Rojek J., Nosewicz S., Pietrzak K., Chmielewski M., Simulation of powder sintering using a discrete element method, VII International Symposium on Mechanics of Materials and Structures, 2013-06-03/06-06, Augustów (PL), pp.59-60, 2013
9.Rojek J., Nosewicz Sz., Pietrzak K., Chmielewski M., Kaliński D., Discrete element simulation of powder metallurgy manufacturing process of metal-ceramic composites, ECCOMAX 2012, 6th European Congress on Computational Methods in Applied Sciences and Engineering, 2012-09-10/09-14, Wiedeń (AT), pp.1-2, 2012
10.Nosewicz Sz., Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Kačianauskas R., Discrete Element Modelling of Solid State Sintering Process of Metal-Ceramic Composite, SolMech 2012, 38th Solid Mechanics Conference, 2012-08-27/08-31, Warszawa (PL), pp.172-173, 2012
11.Rojek J., Nosewicz S., Pietrzak K., Chmielewski M., Kaliński D., Modelling of powder sintering using the discrete element method, CMM 2011, 19th International Conference on Computer Methods in Mechanics, 2011-05-09/05-12, Warszawa (PL), pp.241-1-2, 2011
12.Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Discrete element modelling of powder sintering, SolMech 2010, 37th Solid Mechanics Conference, 2010-09-06/09-10, Warszawa (PL), pp.64-65, 2010
13.Węglewski W., Basista M., Pietrzak K., Thermal stress and microcracking in the processing of the interpenetrating phase composites, SolMech 2010, 37th Solid Mechanics Conference, 2010-09-06/09-10, Warszawa (PL), pp.118-119, 2010
Węglewski W., Basista M., Pietrzak K., Thermal stress and microcracking in the processing of the interpenetrating phase composites, SolMech 2010, 37th Solid Mechanics Conference, 2010-09-06/09-10, Warszawa (PL), pp.118-119, 2010

Abstract:
The interpenetrating phase composites (IPC) are strongly different in their morphology, properties and processing than typical metal matrix or ceramic matrix composites. The basic morphological difference in comparison with particulate reinforcement composites is that the two components of IPC form continuous, interpenetrating 3D network. The IPC are more homogeneous, have better mechanical and thermal properties (abrasibility and fracture toughness, thermal conductivity and mechanical stability) than the matrix composites. The processing of IPC is typically done by a pressure or pressureless infiltration of ceramic porous matrix with a molten metal. The infiltration is a high temperature process (e.g. for Cu/Al2O3 IPC the infiltration temperature is above 1200OC and for Al/Al2O3 about 700 OC) which is usually associated with the generation of thermal stresses because of largely different coefficients of thermal expansion of the IPC components. The aim of this work was twofold: (i) to build a numerical model of thermal stress generated during the processing of the interpenetrating phase composites, and (ii) to build a numerical model of the initiation and growth of microcracks induced by the thermal stresses during the processing of the IPC. The results yielded by the models were compared with the experimental data. The models can be used to improve the processing of IPC by providing feedback as to how to reduce thermal residual stresses and how to minimize a risk of the microcracking during the production of the IPC.

Keywords:
interpenetrating phase composites, residual stress, microcracking, damage modelling

14.Rojek J., Pietrzak K., Chmielewski M., Kaliński D., Constitutive modelling of sintering processes using the discrete element method, Workshop on Constitutive Modeling in Applications for Industrial Processes, 2010-09-01/09-03, Kraków (PL), pp.1-2, 2010