Institute of Fundamental Technological Research
Polish Academy of Sciences

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Barbara Grzegorczyk



Recent publications
1.  Ozgowicz W., Grzegorczyk B., Pawełek A., Wajda W., Skuza W., Piątkowski A., Ranachowski Z., An analysis of the Portevin- Le Chatelier effect and cracking of CuSn6P alloy at elevated temperature of deformation applying the acoustic emission method, ENGINEERING FRACTURE MECHANICS, ISSN: 0013-7944, DOI: 10.1016/j.engfracmech.2016.04.036, Vol.167, pp.112-122, 2016

Abstract:
The paper concerns the application of the acoustic emission (AE) method for the determination of the mechanical properties of continuously cast industrial tin bronze CuSn6P, which reveals tendencies to unstable plastic flow connected particularly with the Portevin–Le Chatelier (PLC) effect. The relations between the jerky flow connected with the PLC effect, AE intensity and the evolution of a fracture of the investigated alloy subjected to the tensile and compression tests have been analyzed. It has been found that the intensity of the oscillation of stresses, observed on the curves σ–ε, coincides with the effect of the instability of plastic deformation PLC type and the recorded signals of the intensity of acoustic emissions. It has also been found that the increase of the tensile temperature in the investigated alloy involves changes in the mechanism of cracking from transcrystalline ductile to brittle intercrystalline, characteristic at the temperature of minimum plasticity (DMT).

Keywords:
Copper alloy, Portevin–Le Chatelier phenomenon, Fractography, Acoustic emission, Intercrystalline fracture

Affiliations:
Ozgowicz W. - other affiliation
Grzegorczyk B. - other affiliation
Pawełek A. - other affiliation
Wajda W. - other affiliation
Skuza W. - other affiliation
Piątkowski A. - Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Ranachowski Z. - IPPT PAN
2.  Ozgowicz W., Grzegorczyk B., Pawełek A., Wajda W., Skuza W., Piątkowski A., Ranachowski Z., Relation between the plastic instability and fracture of tensile tested Cu-Sn alloys investigated with the application of acoustic emission technique, Frattura ed Integrità Strutturale, ISSN: 1971-8993, DOI: 10.3221/IGF-ESIS.35.02, Vol.35, pp.1-10, 2016

Abstract:
The work concerns the application of the acoustic emission (AE) method in testing the mechanical properties of continuously cast industrial tin bronze CuSn6P, which reveals tendencies to instable plastic flow connected particularly with the Portevin-Le Chatelier (PLC) effect. The relations between the jerky flow connected with the PLC effect, AE intensity and the evolution of a fracture of the investigated alloy subjected to the tensile test at a strain rate (?? ) of about 1.2·10-3s-1 in the range of temperatures (20÷400?C) has been analyzed. It has been found that the highest intensity of the oscillation of stresses, corresponding to the instability of plastic deformation PLC occurred at 200?C, whereas the maximum of the AE activity is at about 200÷250?C. The brittle intergranular fracture starts in the range of equicohersive temperature (TE) of about 200?C. Plastic deformation of the investigated alloy in the range of the temperature of minimum plasticity, amounting to about 400?C, results in intercrystalline fractures on the entire surface of the stretched samples.

Affiliations:
Ozgowicz W. - other affiliation
Grzegorczyk B. - other affiliation
Pawełek A. - other affiliation
Wajda W. - other affiliation
Skuza W. - other affiliation
Piątkowski A. - Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Ranachowski Z. - IPPT PAN
3.  Pawełek A., Piątkowski A., Wajda W., Skuza W., Tarasek A., Ozgowicz W., Grzegorczyk B., Ranachowski Z., Kúdela S., Kúdela Jr S., Mechanisms of plastic instability and fracture of compressed and tensile tested Mg-Li alloys investigated using the acoustic emission method, Frattura ed Integrità Strutturale, ISSN: 1971-8993, DOI: 10.3221/IGF-ESIS.35.03, Vol.35, pp.11-20, 2016

Abstract:
The results of the investigation of both mechanical and acoustic emission (AE) behaviors of Mg4Li5Al alloy subjected to compression and tensile tests at room temperature are compared with the test results obtained using the same alloy and loading scheme but at elevated temperatures. The main aim of the paper is to investigate, to determine and to explain the possible influence of factors related with enhanced internal stresses such as: segregation of precipitates along grain boundaries or solute atoms along dislocations (Cottrell atmospheres) or dislocation pile-ups at grain boundaries which create very high stress concentration leading to fracture. The results show that the plastic instabilities are related to the Portevin–Le Châtelier phenomenon (PL effect) and they are correlated with the generation of AE peaks. The fractography of breaking samples was analyzed on the basis of light (optical), TEM and SEM images.

Affiliations:
Pawełek A. - other affiliation
Piątkowski A. - Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Wajda W. - other affiliation
Skuza W. - other affiliation
Tarasek A. - other affiliation
Ozgowicz W. - other affiliation
Grzegorczyk B. - other affiliation
Ranachowski Z. - IPPT PAN
Kúdela S. - Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
Kúdela Jr S. - Institute of Materials and Machine Mechanics, Slovak Academy of Sciences (SK)
4.  Ozgowicz W., Grzegorczyk B., Pawełek A., Piątkowski A., Ranachowski Z., Influence of the strain rate on the plc effect and acoustic emission in single crystals of the CuZn30 alloy compressed at an elevated temperature, Materials and Technology, ISSN: 1580-2949, DOI: 10.17222/mit.2013.195, Vol.49, No.2, pp.197-202, 2015

Abstract:
The purpose of these investigations was to determine the effect of the strain rate on the phenomenon of a heterogeneous plastic deformation of the Portevin–Le Chatelier type while testing free compression of CuZn30 single crystals with a crystallographic orientation of [139] at 300°C. Moreover, the relations between the work-hardening curve s–e displaying the PLC effect and the characteristics of the signals of the acoustic emission generated in the uniaxial-compression test were determined. It was found that the process of plastic deformation of the tested single crystals in the analyzed range of the frequencies up to 35 kHz generates differentiated sources of acoustic-energy emission, mainly the impulsive emission generated by signal events, correlated with the oscillations of the stresses on the work-hardening curves s–e. The strain rate mainly causes the changes in the intensity of the oscillation typical for the PLC effect.

Keywords:
plastic strain, Portevin–Le Chatelier effect (PLC), single crystals, copper alloys, compression test, acoustic emission (AE)

Affiliations:
Ozgowicz W. - other affiliation
Grzegorczyk B. - other affiliation
Pawełek A. - other affiliation
Piątkowski A. - Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Ranachowski Z. - IPPT PAN
5.  Ozgowicz W., Grzegorczyk B., Pawełek A., Piątkowski A., Ranachowski Z., The Portevin – le Chatelier effect and acoustic emission of plastic deformation CuZn30 monocrystals, ARCHIVES OF METALLURGY AND MATERIALS, ISSN: 1733-3490, DOI: 10.2478/amm-2014-0029, Vol.59, No.1, pp.183-188, 2014

Abstract:
The paper presents the investigation of the relation between the acoustic emission (AE) and instability of plastic deformation type Portevin-Le Chatelier (PLC) of single-phase brass CuZn30 monocrystals with crystallographical orientation [1¯3 9]. The monocrystals have been investigated applying the method of free compression at a constant strain rate and the temperature within the range from 200°C to 400°C, simultaneously recording PLC phenomenon by means of acoustic emission. During hot axial compression tests the correlation between work-hardening curves σ - ε, which display PLC effect and characteristic of acoustic emission signals has been found. Moreover, it was proved that in the range of the PLC effect, the acoustic signal is an impulse a character of cyclic repeatability, distinctly correlated qualitatively with the stress oscillations on the curves σ - ε. The analysis of the obtained results leads to the conclusion that in the tested monocrystals the effect PLC is probably controlled by complex processes similar to the phenomenon of dynamic strain ageing (DSA), which are described by diffusion models.

Keywords:
plastic strain, Portevin - Le Chatelier effect (PLC), monocrystals, copper alloys, compression test, acoustic emission (AE)

Affiliations:
Ozgowicz W. - other affiliation
Grzegorczyk B. - other affiliation
Pawełek A. - other affiliation
Piątkowski A. - Institute of Metallurgy and Materials Science, Polish Academy of Sciences (PL)
Ranachowski Z. - IPPT PAN

Conference papers
1.  Ozgowicz W., Grzegorczyk B., Pawełek A., Piątkowski A., Ranachowski Z., Acoustic Emission and the PLC Effect in Compressed CuZn Monocrystals, 58th Open Seminar on Acoustics joined with 2nd Polish-German Structured Conference on Acoustics, 2011-09-13/09-16, Jurata (PL), Vol.2, pp.159-168, 2011

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