HREM observations of mechanical twinning in Cu-Ti alloys: Structure of incoherent and coherent twin interfaces

Abstract

The flow of Cu-Ti alloys hardened by coherent β′ precipitates (Cu4Ti, D1a superstructure) is particularly interesting since these alloys show profuse twinning on multiple systems after small amounts of plastic flow by slip. In this paper, studies of the fine-scale structure of the mechanical twins which form in particle hardened Cu-Ti alloys are reported. The growth of deformation twins occurs via the motion of G-ledges at twin/matrix interfaces and via a coalescence of fine twins. The atomic structure of the coherent twin/matrix interfaces and associated single and multiple layer ledges are characterized. Incoherent interfaces at the tip of deformation twins generated by 90° and 30° twinning dislocations have been investigated.