Strength-ductility trade-off modulated by thermo-kinetic synergy of heat-treatable aluminum alloys

Abstract

The strength-ductility trade-off behaviors for most metallic alloys are intrinsically depend on various microstructures formed during materials processing. Thermodynamics and kinetics of the involved phase transformation and concurrent/subsequent deformation play important roles in determining the overall microstructures and final performances. Since the mechanical responses of aluminum alloys can be mediated by introduction of nano-sized precipitates, taking the heat-treatable Al–Mg–Si alloys as representative, we herein investigate the strength-ductility trade-off behaviors from the thermo-kinetic synergy upon precipitation. It turns out that typical combination of high strength and large ductility for Al–Mg–Si alloys corresponds to certain synergistic effect between thermodynamics and kinetics, as reflected by large driving force and high energy barrier of precipitation, which is modulated by specific heat-treatment conditions. Such formulation of the strength-ductility and thermo-kinetic trade-off correlation has potential implications for guiding alloys design, as exemplified by the Al-0.46Mg-1.04Si alloy aged at 438 K with ideal strength and ductility match. The underlying mechanisms are illustrated via systematical analysis on the crystallography, thermodynamics and kinetics during precipitation of Al–Mg–Si alloys. Our investigation provides an innovative strategy to understand the strength-ductility trade-off phenomenon in light of the thermo-kinetic synergy, as dominated by composition and processing routes of metallic alloys.