Microstructure and Mechanical Properties of TiAl-Ti₂AlC Composites Produced by Combustion Reaction Process

Abstract

To enhance the negligible low-temperature ductility and low high-temperature strength of titanium aluminides, TiAl-Ti₂AlC composites were made by the combustion reaction process, following arc-melting. The alloy compositions included Ti₅₂Al₄₃C₅, Ti₅₀Al₄₅C₅ and Ti₄₈Al₄₇C₅ in at%. The resulting composites had about l8vol%Ti₂AlC in the matrix TiAl with a lamellar structure of Ti₃Al. In the annealed specimens, smaller particles were visible in the matrix, and appeared to form in place of solutionizing lamellae. Therefore, carbon atoms in the matrix, probably in the Ti₃Al phase, formed carbide Ti₂AlC particles with the smaller sizes. On the other hand, the behavior with regard to change in lattice parameters and Vickers hardness suggested a reduction in the solubility of carbon in the TiAl phase with decrease in annealing temperature. For the Ti₅₀Al₄₅C₅ alloy, annealed at 1273K, ambient-temperature ductility up to 0.9% was achieved in bending.