An experimental and computational framework to investigate the thermal cycling approach for strengthening low SFE FeMnNi medium entropy alloy

Abstract

Thermal cycling treatment was adopted for the microstructural engineering of a ternary equiatomic FeMnNi medium entropy alloy (MEA) for achieving different strength-ductility combinations using instrumented indentation and electron backscatter diffraction. A computational model based on cellular automata that accounts for the thermodynamic and kinetic aspects of microstructural evolution was used for predicting recrystallization and grain growth during conventional isothermal single-step and cyclic annealing. The current investigation suggests that an equivalent isotemporal thermal cycling treatment produces a recrystallized microstructure of lower average grain size with a more uniform grain size distribution and a lower variance as a result of inhibition of grain growth. Superior strength-ductility combinations are obtained for all the thermal cycling samples compared to single-step annealed samples. The thermally cycled recrystallized sample demonstrated a yield strength of 561±10 MPa with ductility of 46.7±3.5% against the isothermally recrystallized sample with a yield strength of 406±11 MPa and elongation up to 35.1±5.2%. Thus, the present study demonstrates that thermal cycling treatment provides superior control over the microstructure and optimum combination of strength and ductility in FeMnNi MEA.