MICROSTRUCTURE EFFECT ON ENHANCEMENT OF ROOM-TEMPERATURE DUCTILITY IN β-Ti CONTAINING γ-TIAL BASED ALLOYS

Effects of microstructure constituents of alpha(2)-Ti3Al/gamma-TiAl lamellae, beta-Ti grains and gamma grains, with various volume fractions on room-temperature ductility of gamma-TiAl based alloys have been studied. The ductility of the alloys containing beta phase of about 20% in volume increases to more than 1% as the volume fraction of gamma phase increases to 80%. However, gamma single phase alloys show very limited ductility of less than 0.2%. Microstructure analysis have revealed that intragranular fracture along gamma/gamma grain boundary occurred in y single phase alloy whereas it does not along beta/gamma interphase in alloys containing beta phase. In addition, local strain accumulations along beta/gamma interphase have been confirmed. The present results, thus, confirmed the significant contribution of beta phase, especially the existence of beta/gamma interphase to enhancement of the room -temperature ductility in multi-component TiAl alloys.