Influence of Mo content on microstructure and mechanical properties of β-containing TiAl alloy

The influence of Mo content on the microstructure and mechanical properties of the Ti-45Al-5Nb-xMo-0.3Y (x=0.6, 0.8, 1.0, 1.2) alloys was studied using small ingots produced by non-consumable electrode argon arc melting. The results show that small quantities of β phase are distributed along γ/α₂ lamellar colony boundaries as discontinuous network in the TiAl alloys owing to the segregation of Mo element. The γ phase forms in the interdentritic microsegregation area when the Mo addition exceeds 0.8%. The β and γ phases can be eliminated effectively by subsequent homogenization heat treatment at the temperature above T_α. The evolution of the strength, microhardness and ductility at different Mo contents under as-cast and as-homogenization treated conditions was analyzed, indicating that excessive Mo addition is prone to cause the microsegregation, thus decreasing the strength and microhardness obviously, which can be improved effectively by subsequent homogenization heat treatment.