Influence of secondary γ' phase evolution on creep properties of single crystal superalloy DD6

Abstract

The effect of secondary γ' phase evolution on the creep properties of single crystal superalloy DD6 was investigated at 760℃/785 MPa and 980℃/250 MPa by FESEM and TEM. The results indicate that the secondary γ' phases in DD6 alloy with standard heat treatment are precipitated in the matrix channel after exposure at 1120℃/4 h/AC. Since the secondary γ' phases in the matrix prevent the a/2〈011〉 dislocation gliding in the matrix channel and promote the {111}〈112〉 slip operated in the primary γ' phases at the beginning of creep at 760℃/785 MPa, the secondary γ' phases in the matrix channel decrease the incubation period and significantly improve the primary strain and creep rate. The secondary γ' phases in the matrix will dissolve rapidly at the beginning of creep at 980℃/250 MPa, therefore, the secondary γ' phases have no influence on the creep behaviour of 980℃/250 MPa.

Keywords

• single crystal superalloy
• secondary γ' phase
• creep behaviour
• dislocation
• dd6