如何使合金兼具高强度与高塑性

Increasing the yield strength of metallic materials is observed to almost always substantially reduce their tensile ductility. Here we unravel the origin of this perplexing“strength-ductility tradeoff”, and conclude that this dilemma does not necessarily preclude concurrent high strength and high ductility. We discuss several strengthening and work hardening mechanisms that regulate dislocation behavior, including traditional ones that have been pushed to their extreme in recent years, as well as new ones that take advantage of the heightened structural and chemical heterogeneities; all these mechanisms are rendered more powerful by emerging complex concentrated alloys that bring in multiple principal elements. These mechanisms, while offering elevated strength, contribute to sustainable strain hardening under high flow stresses, delaying strain localization to allow prolonged uniform elongation. The current status in the pursuit for concurrent high strength and high ductility is reviewed. The goal we set for high yield strength ~2 GPa (rivaling super steels) together with large uniform elongation ~30% (much like un-strengthened elemental metals) is projected to be soon within reach. These take-home messages shed light on some existing puzzles regarding the strength-ductility synergy, and offer new insight into the innovative design of alloys.