Deformation mechanisms during high temperature tensile creep of Ti3AlC2 MAX phase

The deformation mechanisms involved in the tensile creep of a Ti3AlC2 specimen deformed, at 900 °C, to a 7.5% final strain are investigated through SEM and TEM observations. Tensile creep strain rate analyses on Ti3AlC2 deformed at 900 °C enabled to identify a Norton's law with a n coefficient around 2, suggesting that creep mechanisms are controlled by grain boundary sliding. TEM observations revealed a highly heterogeneous microstructure consisting in both grains without any dislocations and grains highly defected. This intragranular deformation involves three different microstructural features: dislocations mainly confined in the basal planes and possibly organized in hexagonal networks, numerous stacking faults, and original lenticular non planar defects that likely play an important role in the sample deformation. The deformed microstructure observed and the estimated Norton coefficient suggest that intergranular deformation play an additional important role in the deformation mechanisms.