Tailoring stacking fault energy for high ductility and high strength in ultrafine grained Cu and its alloy

Bulk ultrafine grained (UFG) materials produced by severe plastic deformation often have low ductility. Here the authors report that simultaneous increases in ductility and strength can be achieved by tailoring the stacking fault energy (SFE) via alloying. Specifically, UFG bronze (Cu 10wt.% Zn) with a SFE of 35mJ∕m2 was found to have much higher strength and ductility than UFG copper with a SFE of 78mJ∕m2. Accumulations of both twins and dislocations during tensile testing play a significant role in enhancing the ductility of the UFG bronze. This work demonstrates a strategy for designing UFG alloys with superior mechanical properties.