Strain rate sensitive microstructural evolution in a TRIP assisted high entropy alloy: Experiments, microstructure and modeling

Compressive response of a novel Fe38.5Mn20Co20Cr15Si5Cu1.5 high entropy alloy with transformation induced plasticity made by laser powder bed fusion was studied at quasi-static, medium and high strain rates. Mechanical response and variation in work hardening rate with strain rate were correlated with gamma (f.c.c.) -> epsilon (h.c.p.) martensitic transformation, subsequent phase evolution and adiabatic heating. A strong near basal {0 0 0 1} texture observed in the transformed epsilon (h.c.p.) phase after deformation was correlated with the initial texture, gamma (f. c.c.) -> epsilon (h.c.p.) transformation orientation relationship, as well as the activated deformation mechanisms in epsilon (h.c.p.) phase. The initial c/a ratio of 1.612 for the epsilon (h.c.p.) phase evolved with deformation and this was quantified to understand the propensity of non-basal < c+a > slip activation. Metastable gamma (f.c.c.) dominant microstructure in the as-built alloy enabled excellent hardening via gamma (f.c.c.) -> epsilon (h.c.p.) transformation accompanied by activation of non-basal < c+a > slip and twinning. Experimental results were correlated with existing empirical constitutive models such as Johnson-Cook, Modified Zerilli-Armstrong, Khan-Huang-Liang and Khan-Liu; the Khan-Liu model evidenced the best correlation with experimental results.

Automated summary

The compressive response of a novel Fe38.5Mn20Co20Cr15Si5Cu1.5 high entropy alloy fabricated by laser powder bed fusion was studied at different strain rates. The mechanical response and work hardening rate were found to be correlated with martensitic transformation, phase evolution, and adiabatic heating. Experimental results showed the best correlation with the Khan-Liu model among existing empirical constitutive models.