Influence of Hf Alloying on Precipitation Behavior of γ' Phase and Tensile Properties of Ni-Cr-Mo Alloy

Abstract:

The influence of Hf on the precipitation behavior of γ' phase and the subsequent tensile properties of a Ni-Cr-Mo alloy after long-term thermal exposure was investigated. The results reveal that the addition of Hf increases the average diameter of γ' phases after thermal exposure at 700 ℃ for 5000 h, which enhances the critical resolved shear stress required for dislocations to shear the γ' phases in the Ni-Cr-Mo alloy. Simultaneously, element Hf incorporated into the γ' phases increases the lattice mismatch between the γ' and γ phase, thereby strengthening the coherency strengthening effect. These two factors collectively contribute to the enhanced strength of the alloy. Thus, Hf alloying effectively improves the yield strength of the Ni-Cr-Mo alloy after thermal exposure at 700 ℃.