Effects of carbon and boron addition on microstructure and mechanical properties of TiAl alloys

The effects of carbon or boron addition on microstructure, mechanical properties, phase composition and distribution of the carbides and borides in Ti-48Al alloys were studied in this paper. Carbon and boron were added into Ti-48Al by various styles, such as boron powers or carbon powers, TiB2 and TiC powers and B4C powers. The ingots were prepared by induction skull melting (ISM) with a water-cooled copper crucible. The tensile tests and fracture toughness tests at room temperature were investigated. Meanwhile, the as-cast microstructures were analyzed by the scanning electron microscope (SEM) and the transmission electron microscope (TEM). The grain sizes were estimated by a line intercept technique on at least ten OM micrographs and EBSD. It could be observed that the Ti-48Al alloys containing 0.2 at.%B4C with smaller grains exhibited the excellent tensile strength and elongation among the alloys, 517 MPa and 0.471%, respectively. The effects of boron and carbon addition on distribution of borides and carbides were analyzed. It could be found that borides and carbides distributing uniformly in microstructure also provided better fracture toughness for Ti-48Al-0.2B4C alloys.