The role of 9R structures on deformation-induced martensitic phase transformations in dual-phase high-entropy alloys

Abstract

The occurrence of transformation induced plasticity (TRIP) effects can be affected by the 9R structure, thus improving the mechanical properties of the alloy. However, the mechanism of the 9R structure during the phase transformation is still unclear. A new microscopic mechanism is proposed in this work, and a crystallographic model is established to explain the FCC→9R→HCP transformation processes. The 9R structure is obtained by adjusting the stacking fault energy (SFE) in Fe40Mn40-xCo20Crx high entropy alloy (HEAs) based on first-principles calculation. The calculations reveal that the interfacial synergism derived from the FCC and 9R structures lowers the cohesive energy and enhances stability. Moreover, the 9R structure provides more HCP phase nucleation cores and enhances the TRIP effect. This work proposes a valuable design concept for developing high-strength ductile structural materials.