Insight into the microstructure and micromechanical behavior and mechanism of the constitutional phase of FeNiCrAl0.63 multi-principal element alloy

The mechanical properties of quaternary Fe-Cr-Ni-Al alloys have been extensively studied due to their potential application in high temperature structural components. However, the work hardening mechanism originating from the two BCC phase states is not clear. Herein, we systematically investigate the constituent phases and the micromechanical behavior of the FeCrNiAlx (x = 0.63, 0.71, 0.77) alloys. Dual-phase microstructural charac-terizations indicate that the ordered BCC2 phase is enriched in Ni-Al elements and the disordered BCC1 phase is enriched in Fe-Cr elements, giving rise to an increase in the partition ratio of dual phases. The work-hardening exponents of the BCC1 and BCC2 phases were evaluated to be 0.459 and 0.464, implying the difference of work hardening behavior and coordinate deformation of the two BCC phases. Meanwhile, the constitutive relation-ships including the modified Ludwik description of the work-hardening behavior of Al0.63 alloy are investigated by nanoindentation measurements. Results show that the outstanding work-hardening response is associated with coordinated deformation of the soft and hard two BCC phases. Furthermore, the first-principles calculation illustrates that the stronger bonding strength of the BCC2 phase contributes to the higher work hardening capability than the BCC1 phase.