The carbide was prepared by reactive hot-pressing and was investigated by means of transmission electron microscopy. The material consisted mainly of large elongated grains with planar boundaries, and contained a low defect density. Dislocations were observed within the grains and at grain boundaries. This was the first reported detailed study of dislocations in this material. Perfect dislocations, with a Burgers vector of 1/3<11•0>, were seen to be lying in (00•1) basal planes. These dislocations were mobile, and multiplied during room-temperature deformation. All of the observed stacking faults lay in basal planes. It was noted that, on the basis of the structure of this carbide, the fact that the defects were confined to basal planes was not surprising. The carbide was a layered hexagonal material in which almost close-packed planes of Ti were separated from each other by hexagonal nets of Si, with every fourth layer being a Si layer. A basal interatomic vector was the shortest full translation vector in the structure. Therefore, perfect dislocations could be expected to have a Burgers vector of 1/3<1¯2•0> and to lie in the basal planes. Other dislocations were much less likely to exist because their Burgers vectors would be relatively large. The (00•1)[11•0] slip system was also common to all hexagonal metals, and it was not surprising that perfect basal plane dislocations with a Burgers vector of 1/3<11•0> should exist in this carbide. It was assumed that, after lengthy annealing at 1600C, any dislocations which were created by plastic flow during hot-pressing would have annealed out. This was consistent with the low defect density which was observed. The arrays of perfect basal dislocations were suggested to have formed during cooling, as a result of thermal residual stresses due to an anisotropy in the thermal expansion coefficients along the c- and a-axes. These dislocations appeared to be emitted from triple junctions of grain boundaries. The stacking faults were suggested to have formed via the dissociation of a perfect dislocation into 2 partials which then bounded the resultant stacking fault. The dissociation reaction was suggested to be:

1/3<11•0>  1/3<10•0> + stacking fault + 1/3<01•0>

Because the perfect dislocation and the 2 partials had Burgers vectors which lay in the same basal plane, the stacking fault bounded by these partials also lay in that plane.

Dislocations and Stacking Faults in Ti3SiC2. L.Farber, M.W.Barsoum, A.Zavaliangos, T.El-Raghy, I.Levin: Journal of the American Ceramic Society, 1998, 81[6], 1677-81