Effect of “γ′ phase and Twin” Composite Structure on Strength and Plasticity of Superalloy

Abstract:

In this paper, different treatments were used to adjust the “γ′phase+twin” structure of a new Ni-Cr-Co based wrought superalloy, which was low alloying and low stacking fault energy. The contribution of twin boundary to grain refinement, strength improvement and the effect of the “γ′phase+twin” structure on the mechanical properties of the alloy were analyzed. The results show that after solution treatment at 1090 ℃ for 1 h, the γ′precipitates in the microstructure of the forged alloy is basically dissolved, and the content of twins in the structure is as high as 51.65%. The elongation (42.9%) of the solid solution alloy is 63.6% higher than that of the forged alloy (26.8%), and the yield strength is 693 MPa (only 3% lower than that of the forged alloy) σ _tb = 66.98 MPa, and its contribution is basically the same as that of fine grain strengthening (77.4 MPa). The content of twins of the aged alloy treated by 700 ℃ / 8 h / AC is 34.41%, at the same time, a large amount of γ′ phase, which is precipitation strengthening phase, is introduced into the structure, and form the“ γ′phase + twin" composite structure. The hardness, tensile strength, yield strength and elongation of the aged alloy (405 HV, 1042 MPa, 864 MPa, 49.76%) are further improved compared with those in the solid solution state (324.4 HV, 879 MPa, 693 MPa, 42.9%) , and σ _tb=107.94 MPa. In superalloys with low alloying and

Key words:Ni-Cr-Co based wrought superalloy; “γ′phase+twin” structure; Twin strengthening; mechanical property