Study Of Microstructure And Mechanical Property Of Forged And Cold Rolled GH4169Alloy Blade

In this paper, the variation of microstructure and mechanical properties of theGH4169alloy blades in the process of forming, heat treatment and long-term aging hasbeing studied systematically. The correlation of the molding process of the blades andits microstructure and mechanical properties has also being discussed. Meanwhile, thestability of the microstructure of the GH4169alloy blades in the long-term agingprocess was also evaluated in this paper. The effect of deformation, heat treatment andlong-term aging process parameter on the changes of grain size， dislocation movementand features of precipitated phases phase in the blades such as size, morphology, and thenumber have being observed using metallographic microscope, scanning electronmicroscopy and transmission electron microscopy. Strengthening mechanisms ofprecipitate phase in the blades has being explained.Results of the solution treatment for the GH4169alloy blades with differentheating-up temperature and soaking time showed that the δ phase precipitated mainlyalong the grain boundary because grain boundary and twin boundary of the GH4169alloy provided a good thermodynamic condition for precipitation of δ phase. δ phaseprecipitated directly from the matrix with the increasing of solution temperature andcould be observed within the grain and along the grain boundaries. With the extensionof the solution temperature and holding time, δ phase gradually dissolved with the shapechanging form a slender needle into a short rod-like, granular. δ phase can inhibited thegrain growth in the GH4169alloy significantly. When the temperature is lower than thecomplete dissolution temperature of δ phase, grain growth is slow because ofundissolved δ phase pinning the grain boundaries. Barriers of δ phase to the grainboundary have been lifted when temperature higher than the complete dissolutiontemperature of δ phase, grain size grow up rapidly.Results of the room temperature compression deformation of the GH4169alloyblades in different deformation amount showed that the δ phase precipitated firstlyalong the grain boundary, and growed from grain boundary to grain interior, and thenprecipitated along the deformation bands. The higher the degree of deformation, thesuper-space generated during the deformation would be more, non-equilibriumsegregation of Nb atoms would be more serious. These changes could reduce the criticalnucleation energy of δ phase and promote the γ"â†'δ conversion.The heat treatment of GH4169alloy blades in different conditions showed that theprecipitation of disc-shaped γ" phase occurred mainly at high-temperature aging process,the precipitation of granular γˊphase come up mainly at low-temperature aging process.The γ"â†'δ conversion could occur whether in the high-temperature or low-temperature aging process. More γ" and γˊphase distributed diffusely in the matrix of the GH4169alloy blades could be obtained under the heat treatment of975℃×1h, AC+720℃×8h,50°C/h, FC to620℃+620℃x8h, AC, meanwhile, the amount of γ"â†'δconversion was less, the alloy could get the maximum hardness value.Results of the long-term aging experiments of the blades in different temperatureand time showed that the GH4169alloy maintained a good long-term aging stability at580℃and900hours, the microstructure of the blades was essentially unchanged, thehardness value of the blades increased because of the secondary precipitation of γ"phase and γˊphase.