Creep deformation of DD15 single crystal superalloy at 980°C/250MPa

Abstract The creep deformation behavior of DD15 alloy was studied under the condition of 980°C/250MPa. The microstructure characteristic and dislocation feature were analyzed after the different creep strain. The creep strain was 0.2%, 0.5%, 1%, 2% and rupture, respectively. The result shows that the creep properties at 980°C/250MPa of DD15 alloy was very good. The first stage creep life was relatively short. When the strain of the alloy was 0.2%, the creep deformation process had already been into the second stage. The second stage creep life was relatively long, which is the majority of the whole life. When the alloy strain was 2%, the creep was in the tertiary stage in which the creep rate increased significantly. The γ′ precipitates were rafted for all the specimens with different strain, and the dimension of raft row in the stress direction slightly grew up as the strain rised. The TCP phase did not precipitated for all samples with different strain. The above results indicate that DD15 alloy has excellent microstructure stability. The dislocation network formed on the two-phase interfaces, and a few dislocations cut into γ′ precipitates in creep specimen deformed with 0.2% strain. With increase of creep strain the dislocation network of sample turned denser.