Transformative high entropy alloy conquers the strength-ductility paradigm by massive interface strengthening

Recent metastable alloy designs have demonstrated simultaneous attainment of high ultimate tensile strength (UTS) and ductility in high entropy alloys but with low yield strength. Here we present new strategy for improving the work hardenability and yield strength (YS) together in Fe38.5Mn20Co20Cr15Si5Cu1.5 high entropy alloy (Cu-HEA). Drastic increase in the YS (1.5 GPa) is attributed to the formation of gamma/epsilon, epsilon/epsilon (twin type) and epsilon/epsilon (plate type) interfaces in the microstructure due to extreme grain refinement whereas high UTS-ductility synergy (2.2 GPa, 15%) is attained by dynamic Hall-Petch hardening across these interfaces (i.e. massive interface strengthening) and transformation induced plasticity in gamma phase. Thus, this harmonious combination of YS and UTS-ductility synergy in Cu-HEA outperform all structural materials till date. Therefore, deformation-induced massive interface strengthening is a new, yet cost-effective pathway for synergizing the benefits of advanced steels and high entropy alloys together in a material by conventional processing route. (C) 2021 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Automated summary

The study demonstrates a novel approach to achieve high strength and ductility synergy in Cu-HEA by combining different interface formations and hardening mechanisms. This new alloy design is expected to open up new directions in materials science, balancing performance with cost-effectiveness.