Stacking fault formation in perovskite Ti3AlC carbides in a TiAl based alloy during creep at 800°C

Abstract

The interaction between dislocations and perovskite Ti3AlC precipitates in Ti-45Al-5Nb-0.75C after being crept at 800 °C was investigated by aberration corrected transmission electron microscopy. The results show that Ti3AlC carbides can be sheared by dislocations, but unlike dislocation activity reported in other perovskite structures, stacking faults and crossed stacking fault configurations form. The stacking fault formation is induced by the shear of 1/6<112> Shockley partial dislocations that resulted from the dissociation of 1/2<110> partial dislocations. Due to enhanced local atomic reordering processes at 800 °C, nearest neighbor atom violation of the complex stacking faults was relieved and thus stacking fault formation was promoted in Ti3AlC carbides. By glide of partial dislocations, stacking faults extended along {111} planes and encountered each other to form crossed stacking fault configurations. The resulting stair-rod arrangement might further strengthen the precipitates, and thus make them strong obstacles for dislocation gliding at 800 °C.