The structure and associated formation mechanism of deformation twins in Cu-Nb alloy

摘要

The microstructure and associated formation mechanisms of deformation twins (DTs) in Cu-Nb alloy prepared by mechanical alloying (MA) at room temperature have been investigated by transmission electron microscope (TEM) and high-resolution TEM (HRTEM) observations. The results show that DTs form in Cu grains with sizes around or below 100 nm. Here, two different types of twins have been observed. One type of twins is nucleated via partial dislocation emission from grain boundaries (GBs). A dislocation based model reveals that decreasing grain size and increasing stress concentration benefit the partial dislocation emission. The other type of twins is formed via the splitting and migration of GBs. These twinning mechanisms are totally different with that accessible to coarse-grained Cu.