Effect of heat treatment on microstructure and mechanical properties of directionally solidified superalloy DZ12

The effect of heat treatment on the microstructure and mechanical properties of directionally solidified superalloy DZ12 was investigated in this paper. The results show that higher the solid solution temperature is and longer the solid solution duration is, more γ′ and eutectic (γ+γ′) phases dissolved into γ phase, and more fine cuboidal γ′ phase reprecipitated. γ′ phase grew up obviously and became more cuboidal during aging treatment. Heat treatment increases the stress rupture life of DZ12 alloy under 1100 °C/130 MPa from 55 h of as-cast alloy to 78–112 h, resulting from the modification of microstructure. If incipient melting can not occur, higher solid solution temperature and longer solid solution duration is beneficial to improve the high temperature strength of the alloy, as well as aging treatment. The optimum heat treatment for DZ12 alloy is 1270 °C / 1 h + 1280 °C / 2 h + 1290 °C / 4 h, AC + 1100 °C / 4 h, AC + 870 °C / 20 h, AC.