Combining structural and chemical heterogeneities on the nanoscale to enable ductile solid solution with record-high specific strength

Abstract

Heterogeneous nanostructuring can strengthen metallic materials without excessive degradation in strain hardening and ductility. Here we show that the complex concentrated make-up in multi-principal element alloys makes it feasible to combine structural and chemical heterogeneities together, both at high levels and on the nanoscale, as demonstrated in a lightweight (Ti₅₅V₃₀Zr₁₅)₉₅Al₅ alloy (∼ 5.16 g/cm³). First, the pronounced local chemical ordering (LCO) promotes “dislocation channels” upon room-temperature rolling. This micro-deformation localization induces numerous nano-deformation bands, many of which are refined into nanocrystalline grains during extended cold rolling. Second, subsequent ageing leads to spinodal decomposition, thereby introducing compositional undulations on the nanoscale. Combined structural and chemical heterogeneities promote strengthening and strain hardening, leading to a record-high yield strength (∼ 1.7 GPa) and specific yield strength (326 MPa·cm³·g^-1), while retaining a respectable elongation-to-failure over 10%, a combination unprecedented in previous lightweight alloys. Our success showcases a novel heterogeneity strategy that achieves unusually high strength without hard precipitates, opening a solid solution route towards high-performance lightweight alloys.