2021 Volume 60 Issue 1 Pages 29-34
The effect of stacking fault energy and solid solution effect on the ultrafine grained (UFG) structural evolution during equal channel angular pressing (ECAP) was studied focusing on the transformation from dislocation cell structures to grain structures. To attempt to separate and compare both effects, pure Cu, pure Ag, Cu–Al alloys and Cu–Mn alloys were chosen for materials because the SFE of Cu–Al alloys decreases with increasing Al concentration whereas that of Cu–Mn alloy remains constant with increasing Mn concentration. The results show that the grain size was smaller and the hardness was higher with increasing solute concentration regardless of low or high SFEs. The final grain size of Cu–10Mn reached 71 nm, and this value was smaller than that of Cu–6.8Al which has lower SFE and was assisted by deformation twinning. A decrease of SFE influenced decreasing dislocation cell size associated with the formation of deformation twinning and shear bands in the early stage of ECAP, but had little influence on decreasing grain size in the later stage. In contrary, the presence of solute atoms facilitated the accumulation of dislocations and led to decreasing cell size in the early stage, and delayed the saturation of microstructures due to suppressed dynamic recovery in the later stages.
