Staff

Abstract:
In this study, tubular specimens of Inconel 625 and Inconel 718 were additively manufactured using the Laser Engineered Net Shaping (LENS) technique. Their initial yield surfaces were experimentally determined under biaxial stress loading at 0.005% and 0.01% plastic offset strain. Uniaxial tensile tests showed yield strengths of 509 MPa and 461 MPa, with Young’s moduli of 180 GPa and 171 GPa for Inconel 625 and Inconel 718, respectively. Yield surfaces, fitted using the Szczepiński anisotropic criterion, revealed elliptical shapes with axis ratios below 1.73, confirming moderate anisotropy. Inconel 625 exhibited nearly symmetric yield strengths in tension and compression, with a higher tensile-direction elongation of the surface, whereas Inconel 718 showed stronger directional dependence, reflecting a higher degree of mechanical anisotropy.

Keywords:
Inconel, Yield surface, Additive manufacturing, Laser Engineered Net Shaping

Abstract:
High-entropy alloys (HEA) are a group of modern, perspective materials that have been intensively developed in recent years due to their superior properties and potential applications in many fields. The complexity of their chemical composition and the further interactions of main elements significantly inhibit the prediction of phases that may form during material processing. Thus, at the design stage of HEA fabrication, the molecular orbitals theory was proposed. In this method, the connection of the average strength of covalent bonding between the alloying elements (Bo parameter) and the average energy level of the d-orbital (parameter Md) enables for a preliminary assessment of the phase structure and the type of lattice for individual components in the formed alloy. The designed TiCoCrFeMn alloy was produced by the powder metallurgy method, preceded by mechanical alloying of the initial elementary powders and at the temperature of 1050 °C for 60 s. An ultra-fine-grained structured alloy was homogenized at 1000 °C for 1000 h. The X-ray diffraction and scanning electron microscopy analysis confirmed the correctness of the methodology proposed as the assumed phase structure consisted of the body-centered cubic (BCC) solid solution and the C14 Laves phase was obtained.

Keywords:
HEA, solid solution, laves phase, U-FAST sintering

Keywords:
additive manufacturing, LENS, yield surface, deformation, superalloy, inconel, multiaxial, EBSD, pre-deformation, anisotropy

Keywords:
plastic deformation, Inconel 718, LENS, EBSD

Abstract:
In this paper, double-phase high entropy alloys with the BCC solid solution matrix and the C14 structured intermetallic Laves phase precipitates with the were obtained. The mixture of Co, Cr, Fe, Mn, Ti and CuO powders was sintered at 1000°C for 1 min using innovative high-pulse sintering U-FAST method. Such method allows to obtain complex TiCoCrFeMn and TiCoCrFeMn+5 vol.% CuO double-phase high entropy alloys. The followed annealing process led to the significant improvement of the fracture toughness of 46 % for TiCoCrFeMn alloy and 27 % for TiCoCrFeMn+5vol.%CuO alloy.