Effect of microstructure on Mechanical properties of Ti-Al based alloys

Three types of TiAl-Nb ternary alloys are obtained by arc-melting and heat treatment, which are gamma-TiAl single phase, gamma-TiAl + alpha(2)-Ti3Al duplex phase and gamma-TiAl +alpha(2)-Ti3Al +Nb2Al muliiple phase alloy. The phase stability is studied using X-ray diffractometer and electron probe microanalyzer. Mechanical properties are investigated through compress and tensile tests at RI to 1373K. It is found that, their mechanical properties are related to their microstructures. The deformability of alloy B is better than that of alloy A and C at RT due to small grain size reduced by 112 phase appearance, lamellar microstructure and interfaces. The deformability of alloy B increases significantly with increasing temperature, the elongation of alloy B achieves 40.4% at 1173K. The fracture mode of alloy B changed from brittle transgranular failure at room temperature to ductile intergranular failure at 1173K. While, both of alloy A and C have not increased its deformability at 1173K and showed brittle transgranular failure at both temperatures. Alloy C was a very brittle material at room and high temperature due to Nb2Al phase appearance, which reducing the continuity of (gamma+alpha(2)) lamellar structure.