Intrinsic Ductility from Shear Amorphization: From Pure Metals to Multi-Principal-Element Alloys
Direct links between electronic structure and intrinsic ductility remain elusive for metals. A framework is proposed that reduces the complexities of valence charge distribution, band filling, and shear strain effects into structure-property relationships describing the intrinsic ductility of metals and alloys. Rather than relying on crystal cleavage and dislocation nucleation at preexisting crack tips, we show that a lower energy fracture criterion, i.e., the activation energy density for amorphization, enables accurate predictions of both intrinsic ductility and ductile-to-brittle transition temperatures. From analytical expressions and tabulated ab-initio stiffness constants, lattice parameters, and binary interaction energies, we present a unified theory that reconciles ductile flow in pure metals and solid-solution alloys. Phase diagrams generated for the Nb-Ta-V-Ti system simultaneously explain its high strength and room-temperature tensile ductility, validating this framework as a practical one for rapid design of structural multi-principal-element alloys.