Ratcheting behavior of non-equiatomic TRIP dual-phase high entropy alloy

Ratcheting behavior of metastable dual-phase (FCC+HCP) Fe50Mn30Co10Cr10 high entropy alloy has been investigated for various combinations of mean stress(sigma(m)) and stress amplitude (sigma(a)) at ambient temperature. The experimental results show that the accumulation of ratcheting strain and fatigue life primarily depend on the applied mean stress and stress amplitude combination. Detailed microstructure analyses using electron back scattered diffraction (EBSD), transmission electron microscopy (TEM), and transmission Kikuchi Diffraction (TKD) revealed the activation of multiple deformation mechanisms, including planar slip, deformation-induced twinning (TWIP), and deformation-induced martensitic phase transformation (TRIP) in both the phases. The synergistic operation of these mechanisms with reverse HCP to FCC transformation at local stress concentration regions in the microstructure promoted cyclic hardening leading to an improved low cycle fatigue behavior of the TRIP DP-HEA under asymmetrical stress-controlled cyclic deformation. In a nutshell, the operation of multiple factors responsible for twinning is unique, providing means to design novel multicomponent alloys.