Effect of Indentation Orientation on the Onset of Plastic Deformation for a MAX Phase Ti 2 AlC

Polycrystalline Ti2AlC alloys were prepared by spark plasma sintering of high purity elemental materials, and subsequently annealed at 1500°C for 24 h. Nanoindentation behavior was studied on the grains with their surface normal directions parallel to 〈3362〉, 〈4481〉, 〈0001〉 and 〈1120〉. During loading of nanoindentation, pop–in events were found to occur for all the indentation directions. The critical loads of the first pop–in observed for the indentation directions parallel to 〈1120〉 and 〈0001〉 were higher than those for 〈3362〉 and 〈4481〉. Surface topography around the residual indents suggests that the basal slip dominates the plastic deformation upon indentation. These results suggest that the nucleation of the basal dislocation is a major barrier for the onset of plastic deformation underneath the indenter. [doi:10.2320/jinstmet.J2017042]