Deformation Twinning in a Metal-Intermetallic System: Novel Paradigm for Designing Alloys with Exceptional Strength-Ductility Combination

Abstract

Engineering applications of high strength alloys are often restricted due to their poor tensile elongation or ductility. Alloys with high yield strength typically exhibit limited strain-hardenability (the difference between tensile and yield-strengths), leading to reduced tensile ductility. Deformation twinning, resulting in high strain hardenability, can lead to enhanced tensile elongation in single-phase solid solutions, including high entropy alloys (HEAs). However, alloy systems involving a solid solution matrix strengthened with an intermetallic phase do not exhibit deformation twinning, thus limiting their tensile ductility. We have successfully exploited deformation twinning in a novel HEA, strengthened using nano-lamellar ordered multi-component intermetallic precipitates, leading to an exceptionally high yield strength (~1630 MPa), good tensile ductility (~15%), and ultimate tensile strength (~1720 MPa), higher than any other reported fcc based alloy. Exploiting deformation twinning in a two-phase metal-intermetallic system, offers a new paradigm for addressing the strength-ductility trade-off plaguing alloy design.