Deformation Rate and Temperature Sensitivity in TWIP/TRIP VCrFeCoNi Multi-Principal Element Alloy

Abstract

High-entropy alloys (HEAs) and medium-entropy alloys (MEAs), also sometimes referred to as multi-principal element alloys (MPEAs), present opportunities to develop new materials with outstanding mechanical properties. Through the careful selection of constituent elements along with optimized thermal processing for proper control of structure, grain size, and deformation mechanisms, many of the newly developed HEA systems exhibit superior strength and ductility levels across a wide range of temperatures, particularly at cryogenic deformation temperatures. Such a remarkable response has been attributed to the hardening capacity of many MPEAs that is achieved through the activation of deformation twinning. More recent compositions have considered phase transforming systems, which have the potential for enhanced strengthening and therefore high strength and ductility levels. However, the strain rate sensitivity of such transforming MPEAs is not well understood and requires further investigation. In this study, the tensile properties of the non-equiatomic V10Cr10Fe45Co30Ni5 MPEA were investigated at different deformation rates and temperatures ranging from 77 K (−196 °C) to 573 K (300 °C). Depending on the deformation temperature, the considered MPEA exhibits plasticity through either crystallographic slip, deformation twinning, or solid-state phase transformation. At 300 °C, only slip-mediated plasticity was observed for all the considered deformation rates. Deformation twinning was detected in samples deformed at room temperature, while face-centered cubic to body-centered cubic phase transformation became more favorable at cryogenic deformation temperatures. The trends are nonlinear with twinning-induced plasticity (TWIP) favored at the intermediate deformation rate, while transformation-induced plasticity (TRIP) was observed, although limited, only at the slowest deformation rate. For all the considered deformation rates at cryogenic deformation temperature, a significant TRIP activity was always detected. The extent of TRIP, however, was dependent on the deformation rate. Increasing the deformation rate is not conducive to TRIP and thus hinders the hardening capacity.

Effect of Heat Treatments on Microstructure and Mechanical Properties of Fe-Mn-Ni-Al-Gd Shape Memory Alloy

“…7. FCC () peaks appeared at 2 values of around 43 o , 50 o and 73 o whereas for BCC () peaks are at 38 o , 45 o , 65 o and 88 o [43] [6]. With the addition of Gd, BCC () phase became the dominant phase in the structure without heat treatment.…”

A Fresh Perspective on Medium Entropy Alloys Applications as Coating and Coating Substrate

“…A better understanding of microstructural features and deformation mechanisms is crucial to engineering new alloys with suitable properties for future applications that will require better performance and improved resistance in more extreme environments [22][23][24]. Atomistic methods, such as density functional theory (DFT) and molecular dynamics (MD) are being used to investigate the mechanical properties.…”

Crystal Plasticity Model Analysis of the Effect of Short-Range Order on Strength-Plasticity of Medium Entropy Alloys

“…Due to their remarkable mechanical properties, medium and high entropy alloys (M/HEAs), which include multiple primary elements in almost equal amounts, have recently received a lot of attention [1][2][3][4][5][6][7][8][9][10][11][12][13]. M/HEAs were initially conceived as random solid solutions, with a perfect chemical disorder organization.…”