Effect of temperature on the mechanical behavior of a heterogeneous high entropy alloy

This study presents a comprehensive investigation into the mechanical behavior of a heterogeneous high entropy alloy (HEA) subjected to uniaxial tensile testing across a diverse temperature spectrum, ranging from cryogenic to high-temperature conditions. The study aims to illustrate the alloy s response under transformation induced plasticity (TRIP) mechanism to temperature variations and explore how these temperature shifts affects its mechanical properties. The high entropy alloy under investigation was designed and fabricated to embody a heterogeneous microstructure, incorporating a variety of elemental constituents. The alloy was subjected to uniaxial tensile tests at temperatures encompassing cryogenic conditions (-196 °C), room temperature (+25 °C), and elevated temperature (+400 °C). During testing, various mechanical parameters such as yield strength, ultimate tensile strength, and ductility were measured and the effect of introduced microstructure is analyzed in different phase composition, recrystallization level, and grain size. At cryogenic temperatures, the alloy exhibited exceptional ductility due to the transformation of its microstructure from austenite to martensite (under phase transformation), favoring plastic deformation and inhibiting crack and necking propagation. The unique crystallographic arrangements at lower temperatures contributed to enhanced dislocation mobility, facilitating the alloy s ability to withstand higher strains before failure via improving the strain rate hardening (SHR). In the cryogenic testing condition, the occurrence of TRIP mechanism was the highest and the specimen showed the combination of 1349 MPa strength and almost 20% elongation at fracture point, that showed an enhancement in both strength and ductility compared to other temperatures. As the temperature increased towards ambient levels, the alloy displayed a transition in its mechanical behavior. Microstructural evolution and lattice distortions influenced the alloy s strength, transitioning from a ductile to a more brittle regime. This shift was marked by a significant decrease in yield strength and ultimate tensile strength, accompanied by reduced ductility. At elevated temperatures, the alloy showcased further alterations in its mechanical properties. The progressive softening effect, attributed to dynamic recrystallization and limiting the TRIP mechanism in the microstructure, led to a decline in yield strength and ductility characteristics. This study offers valuable insights into the temperature-dependent mechanical behavior of heterogeneous TRIP-assisted high entropy alloys. Electron Backscatter Diffraction (EBSD) enhanced Scanning Electron Microscopy (SEM) is utilized to support the results. Understanding the interplay of temperature, microstructure, and composition is vital for optimizing the alloy s performance and tailoring its mechanical properties to suit specific application requirements. Therefore, these findings would lay the foundation for further research aimed at maximizing the potential of high entropy alloys in diverse temperature-dependent applications.