P含量对GH4706合金显微组织和持久性能的影响OA

GH4706 alloys with P contents of 0.002％and 0.017％were prepared by vacuum induction melting.Through the design of heat treatment processes,phosphides were precipitated in GH4706 alloy with 0.017％P.The effect of phosphorus(P)existing in the form of phosphides on the microstructure and stress rupture properties of GH4706 alloy was investigated.The research showed that only a small amount of η phase precipitated at grain boundaries in the alloy with 0.002％P.However,the amount of η phase at grain boundaries was significantly increased in the alloy with 0.017％P,with the morphology consisting of blocky,granular,and needle-like shapes.Moreover,the size of η phase was larger in the alloy with 0.017％P.P promoted the precipitation of the η phase by co-segregation with Nb and Ti elements at grain boundaries.Fracture preferentially occurred along grain boundaries rather than within grains in the alloy.Grain boundaries were the pathways for crack initiation and propagation during the stress rupture at 650℃/690MPa.The r]phases at grain boundaries can alleviate stress concentration and hinder the initiation and propagation of intergranular cracks.Therefore,compared to the alloy with 0.002％P,the stress rupture life and elongation were increased by 130.1％and 46.9％respectively in the alloy with 0.017％P.