Temperature-dependent, multi-mechanism crystal plasticity reveals the deformation and failure behaviour of multi-principal element alloys

In this work, we have developed a temperature-dependent, multi-mechanism crystal plasticity (CP) model aimed at unravelling the deformation and failure resistance of Cantor alloy-like multiprincipal element alloys (MPEA) under both uniaxial tensile and cyclic loading conditions. Three deformation mechanisms: dislocation slip, deformation twinning, and phase transformation are considered under a unified stress-driven, thermally activated law. In addition, the effect of shortrange ordering (SRO) is introduced by accounting for the inhomogeneous distributions of material properties within individual grains. Our work yields the following key findings: (1) The rate- and temperature-sensitivity of the materials, such as the occurrence and sequence of dislocation slip, deformation twinning, and martensitic phase transformation observed in experiments can be captured through the calibrated material properties. (2) The enhancement of the mechanical response of the Cantor alloy-like MPEAs due to the SRO effect is intrinsically linked to the generation of geometrically necessary dislocations resulting from localized variations in material properties. (3) The excellent fatigue and fracture resistance exhibited by Cantor alloylike MPEAs at low temperatures can be attributed to the homogenization of stored energy density within the microstructure. This homogenization arises from the development of deformation twinning and martensitic phase transformation. Our newly developed CP model and the key findings provide a valuable guide for the design of MPEAs to achieve superior fatigue and fracture resistance without compromising their inherent strength.