Microstructures and mechanical properties of as-cast TiAl alloys with higher C additions

Abstract

TiAl alloys with higher C additions were fabricated using a XDTM method. The results investigated by XRD, OM and SEM indicated that in Ti-34Al-0.5C alloy, single phase TiC particles and particles having a “core” structure in which the TiC phase was coated by Ti3AlC phase were formed and they uniformly distributed at the grain boundaries. However, when C content is more than 0.5%, the particles with a plate-shape were single phase Ti2AlC and TiC phase coated by Ti2AlC phase. These results suggested that in TiAl alloys with higher C additions, the primary is TiC, and the Ti3AlC and Ti2AlC result from peritectic reaction, L + TiC. The results measured by MPM show that with the increasing of C content, the microhardness both TiC, Ti3AlC and Ti2AlC is higher than that of the matrix Ti3Al and TiAl. However, the elastic modulus of particle phases and matrix has little variation and no change tendency can be found with increasing C content.