Kink-Band Formation in the MAX Phase Ti₂AlC near a TiAl/Ti₂AlC Interface during Nanoindentation

Kink-band formation in Ti2AlC was investigated in a multiphase Ti-Al-C alloy consisting of Ti2AlC, TiAl, and Ti3Al phases. The influence of the TiAl/Ti2AlC interface during nanoindentation was examined. Nanoindentation tests were performed on multiphase polycrystalline alloy specimens, in which Ti2AlC grains with surface normals nearly parallel to [3362] were selected for examination. Nanoindentation behavior in the grain interior was compared with that adjacent to the TiAl/Ti2AlC interface. In the grain interior, deformation was dominated by basal dislocation slip, and kink-band formation was accompanied by basal plane delamination. In contrast, indentation immediately adjacent to the TiAl interface resulted in the formation of ridge-type kink structures without basal plane delamination. The presence of TiAl grains modifies the local mechanical boundary condition during nanoindentation, thereby enabling kink-band formation in Ti2AlC without basal plane delamination.