Elevated-temperature deformation mechanisms in Ta2C: An experimental study

A polycrystalline α-Ta2C bar, fabricated by hot isostatic pressing, was tested in four-point bending at approximately 1930 °C. The sample showed significant plastic deformation. Transmission electron microscopy, using two-beam defect analysis, confirmed pyramidal dislocation slip of the type a/3〈112¯3〉{101¯1}. Basal and prismatic slip of a/3〈112¯0〉 type could not be determined because of significant contrast interference from stacking faults that formed in the material. The increase in stacking fault density observed after thermomechanical loading is not believed to be caused by deformation but rather is due to growth faults that formed from the slight carburization of Ta2C from the graphite heating filaments in the testing apparatus. The significant plasticity accommodation in Ta2C is a result of basal and non-basal slip and the wide spacing of the Ta-Ta metallic bonds that form inherent to its crystallography.