Mechanical property regulation of transformation induced plasticity (TRIP) multi-principal element alloys through multi-phase microstructural design

Abstract

Transformation induced plasticity in multi-principal element alloys involves several types of phase transformation, among which the alloys exhibiting Face-centered cubic (FCC) to Body-centered cubic (BCC) phase transformation during deformation have a place. However, the current multi-principal element alloys with single FCC phase show relatively low room temperature tensile yield strength, thus usage of these alloys is limited for room temperature applications. We report a revised microstructural design by tuning the fractions of FCC and other harder phases via annealing according to equilibrium phase diagrams, which gives rise to both higher yield strength and tensile strength, and still good ductility at room temperature. The increase of the strength can be attributed to the contribution of the harder BCC and Sigma phase particles formed during annealing and the still operational FCC to BCC transformation induced plasticity effect. Hence, properly selected annealing treatment to produce a multi-phase microstructure is a way to exert both the transformation induced plasticity effect meanwhile the composite effect from both soft and hard phases.