Dynamic mechanical performance of FeNiCoAl-based high-entropy alloy: Enhancement via microbands and martensitic transformation

The non-equiatomic FeNiCoAlTaB high-entropy alloy exhibits outstanding quasi-static mechanical properties. Here, we investigate the microstructural evolution and mechanical response of this alloy subjected to dynamic loading, which has not been done before. A novel strategy combining extensive microbanding and martensitic transformation improves the resistance to the plastic instability by deterring the formation of adiabatic shear bands, that only occur beyond a critical shear strain larger than 4. The aged alloy, with grain sizes up to 400 μm, exhibits a dynamic yield stress over 1300 MPa with good deformability in this regime. This investigation sheds light on potential strategies for the enhancement of dynamic mechanical properties of structural materials through the use of a stress-induced martensitic transformation.