Temperature effect on tensile behavior of an interstitial high entropy alloy: Crystal plasticity modeling

Abstract

Previous tensile tests showed that the typical coarse-grained (CG) interstitial high entropy alloy (iHEA) with the nominal composition Fe49.5Mn30Co10Cr10C0.5 (at.%) has higher yield stress and better strain hardening at cryogenic conditions compared to that at room temperature. However, the yield stress of the fine-grained (FG) iHEA is little influenced by decreasing temperature, while the strain hardening is significantly enhanced. The fundamental reasons for these observations need to be further investigated. Thus, a micromechanism-based crystal plasticity model is developed to investigate the temperature effect on the tensile behavior of the iHEA. A thermodynamic model is established to calculate the stacking fault energy of the iHEA at different temperatures. The developed constitutive model is verified by comparing the simulated the stress-strain curves and martensite volume fraction of the CG and FG iHEAs at different temperatures with the corresponding experimental results. Moreover, the contributions of different strengthening mechanisms, such as dislocations, grain boundaries, nano-precipitation, and lattice friction, are quantified to reveal the effect of temperature on the iHEA's yield stress. Furthermore, the grain size effects on deformation twinning and martensite phase transformation are considered. The developed constitutive model is further applied to predict the stress-strain curves of the iHEA with various grain sizes at different temperatures. The present study thus provides a useful modeling tool for understanding the underlying mechanisms of the strength and plasticity in the iHEA, paving a way for optimizing the mechanical properties of advanced alloys at various temperatures.