Stability and amorphization of Cu-Nb interfaces during severe plastic deformation: Molecular dynamics simulations of simple shear

Molecular dynamics is used to investigate in-plane simple shear deformation of three Cu-Nb interfaces with either Kurdjumov-Sachs (KS) or Nishiyama-Wassermann (NW) orientation relationships (ORs). Regardless of the shear direction, both the NW interface and the KS interface with a {1 1 1}fcc||{1 1 0}bcc habit plane consistently deform via pure interface sliding and are highly stable against the shear deformation. In contrast, the KS interface with a {1 1 2}fcc||{1 1 2}bcc habit plane exhibits at small strain various deformation mechanisms along different shear directions. Dislocation glide inside the Cu phase results in a change from the original OR. At large strains, additional strain is accommodated almost entirely by localized shearing at interfacial amorphous layers, which grow as the square root of strain, irrespective of shear direction, phase layer thickness or habit plane. With the onset of such shear localization, a new OR becomes stabilized, although it varies with shear direction. The findings in this study are discussed with respect to structural evolution, amorphization, forced mixing, shear strength and experimental observations.