| Title |
Deformation Twins in a Cu-Ag Nanocomposite Processed by Equal Channel Angular Pressing (ECAP) |
| Authors |
이갑호(Kap Ho Lee); 홍순익(Sun Ig Hong) |
| DOI |
https://doi.org/10.3365/KJMM.2013.51.8.621 |
| ISSN |
1738-8228(ISSN), 2288-8241(eISSN) |
| Keywords |
Cu-Ag nanocomposite; deformation twins; equal channel angular pressing; transmission electron microscopy |
| Abstract |
The nanostructure of a Cu-15wt%Ag composite processed by Equal Channel Angular Pressing (ECAP) was observed by transmission electron microscopy (TEM). ECAP was found to greatly improve the yield strength while maintaining good electrical conductivity. The nanostructured Cu-15 wt%Ag composite contained a high density of {111}/<112> nanotwins and the migration of the twin boundary and detwinning process of those nanotwins was also observed. Nanotwins can be nucleated by bowing out of twinning dislocations at the Cu/Ag interface and propagated by the sequential emission of twinning dislocations on every adjacent twinning plane. Steps having the height of one or three atomic layers on the {111} plane were observed on the coherent twin boundary (CTB). The stair rod dislocation was formed by a cross-slip of 30° partial at one layer high step on the twin boundary, while a cross-slip of 90° partial transformed the incident dissociated dislocation into dissociated dislocation in the twin plane without leaving a stair-rod dislocation behind. The three layer high step was formed by migration of the (111) twin boundary in the direction normal to the twin plane, and it produced a {112} incoherent twin boundary (ITB). The advance or retreat of {112} ITB can lead to the extension or retraction of (111) on the CTB. The detwinning process involves the collective glide of a group of three Shockley partial with different Burgers vectors and the dynamical overlap of stacking faults (SFs) of intrinsically and/or extrinsically dissociated dislocations. †(Received January 7, 2013) |