Papers by Author: Jin Jiang Yu

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Authors: P.C. Xia, Jin Jiang Yu, Xiao Feng Sun, Heng Rong Guan, Zhuang Qi Hu
Abstract: Effect of different aging temperatures on microstructure and stress rupture properties of DZ951 alloy were investigated in this paper. The results show that the shape of carbide changed from script-like in as-cast alloy to block during different aging treatments. MC carbide degrades into M23C6 at the aging temperature of 970°C, which made alloy have a better combination of strength and ductility than that at other aging temperatures. The size of γ′ phase increases and the shape of γ′ phase changed from sphere (870°C) to quasi-cuboid (920°C) and cuboid (970°C) with the increasing aging temperature. The stress rupture life of DZ951 alloy at 1100°C/60MPa improves with the increased of aging temperature. The fractographs at different conditions showed a ductile fracture mode.
Authors: Jin Jiang Yu, Xiao Feng Sun, Tao Jin, Heng Rong Guan, Zhuang Qi Hu
Abstract: Stress rupture and tensile properties of a single crystal superalloy DD32 are investigated comparing with the alloy SRR99. It is shown that the alloy DD32 offers an improved creep temperature capability of more than 60°C at higher stresses. The g¢ precipitates in the stress ruptured samples were rafted to P-N type directional coarsening. The fracture mechanism of the stress ruptured samples was initiated from the micropores.
Authors: Y. Liu, Jin Jiang Yu, Yan Xu, Xiao Feng Sun, Heng Rong Guan, Zhuang Qi Hu
Abstract: Smooth specimens of single crystal (SC) superalloy SRR99 with [001] orientation were subjected to high-cycle fatigue (HCF) loading at temperatures of 700°C, 760°C, 850°C and 900°C in air atmosphere. The results demonstrated that conditional fatigue strength reached the maximum at 760°C and decreases with increasing temperature. Analysis on fracture surface showed a trend for cleavage rupture at 850°C and 900°C and ductile rupture at 700°C and 760°C. Fatigue cracks initiated at the surface or subsurface were primarily responsible for the ultimate failure. The influence of testing temperature on fatigue lifetime was studied by examining evolution of the microstructure through SEM observation. With the process of cyclic loading at elevated temperatures, the primary cuboidal γ′ precipitates tended to agglomerate and spheroidized, meanwhile a larger number of secondary γ′ particles were formed in the γ matrix in specimens fatigue tested at 700°C, which would have a significant effect on the high temperature properties.
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