Thermal stability of nanograins with grain boundary relaxation in microalloyed Cu-Sb and Cu-Fe

Abstract

Grain refinement into nanoscale significantly enhances the strength and hardness of metallic materials but generally reduces the thermal stability by the introduced strong tendency for grain boundary (GB) migration. Stabilizing nanograins through GB relaxation had been proven as an effective way in several metals recently when the grain size is below a critical value. Here, we discovered that the abnormally enhanced thermal stability induced by GB relaxation can be realized in 0.5% Sb or Fe doped Cu, similar to that in pure Cu. The observed critical grain sizes for GB relaxation in the two Cu alloys are almost the same as pure Cu. However, the GB relaxation effect on thermal stability is kind of suppressed compared to pure Cu with similar grain sizes because of the segregation/precipitation of Sb/Fe during the annealing process, which accelerates the detwinning and the failure of relaxed GBs.