Solute synergy induced thermal stability of high-strength nanotwinned Al-Co-Zr alloys

Reducing the grain size into the nanoscale regime in metallic materials provides high mechanical strengths, however at the cost of degrading thermal stability, as grain refinement induces a high driving force for grain coarsening. In this study, we present a solute synergy strategy that stabilizes the microstructures of high strength nanotwinned (NT) Al-Co-Zr alloys. Zr solute additions promote microstructural and mechanical stability up to an annealing temperature of 400 degrees C. In-situ microcompression tests demonstrate concomitant high strengths and deformability in these ternary NT alloys. Density functional theory calculations provide insight into the interplay between Co and Zr solute and how they pin and stabilize incoherent twin boundaries. This work provides a strategy for enhancing both strength and thermal stability of nanocrystalline materials when combining syner-gistic solute pairs.