Stress-Induced Phase Transformation in Single Crystal Titanium Carbide

Single-crystal ingots of TiC were cut into wafer substrates for heteroepitaxial growth of SiC films. During wafer sectioning by abrasive machining, a subsurface damage zone was created. TEM observations of the damage zone revealed a stress-induced martensitic transformation from cubic TiC to rhombohedral and hexagonal structures, both involving an 8.0% contraction normal to the {111} habit plane and a shear along     . It is proposed that the transformed structure is governed by the Ti sublattice, and that carbon atoms remain in octahedral coordination. The transformed phase coarsened to form a lamellar structure consisting of periodic quadlayer twins. The twins imparted hexagonal symmetry, and the lamellar phase was designated 8H. A strain gradient tensor was employed to describe the mapping of atom coordinates between the two phases. The present account constitutes the first report of this transformation in TiC.