Twinning and dislocation activity in silver processed by severe plastic deformation

摘要

In summary, the evolution of the microstructure was studied in Ag processed by ECAP for up to a maximum of 16 passes where Ag was selected because of the excep_tionally low value for the SFE. The results show the change in the microstructural characteristics are consistent with a theoretical model proposed earlier for the deformation of fcc metals and alloys with very low SFE [11]. Up to 1 pass of ECAP there is a rapid'increase in the dislocation density while twinning is marginal (stage I), between 1 and 8 passes both the dislocation density and the twin probability increase significantly (stage II) and between 8 and 16 passes the twin probability further increases but there is a corresponding reduction in the dislocation density (stage III). It is concluded that the contribution of twinning to plasticity increases significantly with increasing strain in fcc metals, such as Ag, where the SFE is very low.