Achieving superb strength in single-phase FCC alloys via maximizing volume misfit

Abstract

Single-phase face-centered cubic (SP-FCC) alloys normally possess low strength. Conventionally strengthening strategies inevitably cause significant ductility sacrifice. Here, a single-phase Ni-based FCC alloy with a superb yield strength of ∼1.05GPa and a good ductility of 37% is designed through maximizing the volume misfits. The misfit of the purposely targeted Ni80Mo20 alloy is severer than all existing FCC alloys, bringing the alloy a highest-ever Hall-Petch coefficient (kHP = 1034 MPa·μm1/2) and a pronounced solid solution strengthening (Δσss = 224 MPa). Current work yields two surprising and novel findings for SP-FCC alloys. First, volume misfit is a good pertinent indicator of kHP. Second, the conventional impression about the sole contribution of edge dislocations to strengthening in SP-FCC alloys may no longer hold; instead, screw dislocations can also kick in once the nonsphericity of the solute-induced stress field reaches a critical value. Altogether, this work paves a new avenue of pursuing ultimate strengthening without significant ductility sacrifice for SP-FCC alloys relying on the volume-misfit-maximization strategy.

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