A pathway to achieving strength–ductility simultaneous improvement via solute segregation in gradient-structured Mg–Zn–Gd alloy

This study reports a novel dual gradient-structured (GS) Mg–2Zn–0.8Gd (wt.%) alloy fabricated via surface sliding friction and followed by heat treatment. Excellent grain boundary (GB) stability is achieved through the co-segregation of Zn and Gd atoms. The segregated gradient structure produces an excellent strengthening and work hardening effect, which is attributed to the combined effects of prominent GB segregation within the GS layer and the recovery of dislocation storage capacity. Furthermore, a remarkable segregation hardening in the surface layer increases the hard–soft disparity, which arouses more geometrically necessary dislocations that further synergistically strengthen and toughen the alloy.