Sugui TIAN
,
Jinghua ZHANG
,
Yongbo XU
,
Zhuangqi HU
,
Hongcai YANG
材料科学技术（英）
The microstructures of a single crystal Ni-base superalloy with [001] orientation were observed by means of TEM. Results showed that the fine gamma' particles were precipitated in the gamma matrix channels during the tensile deformation of the alloy. Thermodynamics analysis indicated that the solubility of elements M(Al,Ta) within the gamma matrix may be changed when the alloy was deformed by the external applied stress. The tensile stress reduced the solubility of elements Al and Ta so as to occur the over-saturation and agglomeration of them, which promoted the precipitation of fine gamma'-phase in the gamma matrix.
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Shishu XIE
,
Tieli WANG
,
Junying LU
,
Hongcai YANG
,
Guangpu ZHAO
材料科学技术（英）
0.020, 0.045 and 0.075 wt pct Zr were added to a Ni-base superalloy GH586 to investigate their effects on the microstructure and the short-term strengths at 850℃. The results showed that proper Zr addition could improve the alloy tensile strength at 850℃and short-term rupture life at 850℃, 580 MPa. Zr exists in both γ' phase and γ matrix, which caused Zr to distribute in grain instead of segregating in grain boundaries, therefore increased both of their lattice parameters but decreased the mismatch between them. Meanwhile, it also increased the amount of grain-boundary carbides and decreased their size markedly. These contributed to the improvement of short-term rupture life. However, further addition of Zr resulted in forming Zr4C2S2, a plate-like stable sulphurocarbides in grain boundaries, which decreased short-term strength at high temperature, and led to a worse hot workability. According to the experimental results, the optimum content of Zr should be 0.020 wt pct.
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