Microstructural characterization and micromechanical properties of dual-phase carbide in arc-melted titanium aluminide base alloy with carbon addition

The microstructure and micromechanical properties of carbides in a near gamma-TiAl base alloy with carbon addition prepared by arc-melting method were investigated. It was observed that there were two types of carbides in the alloy, single-phase TiC and dual-phase carbide. The dual-phase nature of the carbides was identified by transmission electron microscope (TEM) to consist of TiC phase and Ti3AlC phase. In dual-phase carbide, TiC phase acts as the core and nucleation substrate, and the Ti3AlC phase that grows around the core TiC phase acts as the coating layer. The micromechanical properties of dual-phase carbide and the surrounding matrix were examined by nanoindentation tests showing that both microhardness and elastic modulus decrease from the core of dual-phase carbide to the Ti3AlC coating layer and then to the surrounding matrix gradually. The forming mechanism of dual-phase carbide and the role of Ti3AlC coating layer on the mechanical properties were discussed. (C) 2009 Elsevier B.V. All rights reserved.