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通过对传统定向凝固(HRS)及液态金属冷却(LMC)2种工艺制备的镍基单晶高温合金铸态微孔和固溶微孔尺寸与分布的定量表征,分析了制备工艺以及合金成分对单晶合金铸态及固溶微孔形成的影响.结果表明:合金成分的差异导致本研究中HRS合金铸态微孔体积分数低于LMC合金.2种合金经固溶热处理后,在靠近表面的贫Al层及附近均形成大量的圆形固溶微孔,该类微孔的数量随着与表面的远离而减少.高温空气环境下Al向表面扩散形成贫Al层,进而由于Kirkendall效应形成近表面固溶微孔.高温下枝晶干和枝晶间的元素在扩散过程中产生的Kirkendall效应是合金内部固溶微孔的主要成因.LMC合金较小的一次枝晶臂间距和较低的元素凝固偏析程度使得其内部产生的固溶微孔数量远小于HRS合金.
Through the quantitative characterization of the size and distribution of as-cast micropores and solid solution micropores in the nickel-based single crystal superalloy prepared by conventional directional solidification (HRS) and liquid metal cooling (LMC), the effects of preparation technology and alloy composition The results show that the difference of alloy composition leads to the fact that the microscopic pore volume fraction of HRS alloy in this study is lower than that of LMC alloy.The results show that after the solution heat treatment, Of the Al layer and the vicinity of the formation of a large number of round solid solution micropores, the number of such micropores decreases with the surface away from the surface under high-temperature air environment Al diffusion to the surface to form a poor Al layer, and then due to the Kirkendall effect Near-surface solid solution micropore.The Kirkendall effect during the diffusion process of the dendritic dry-dendritic elements at high temperature is the main cause of the intra-solution solid-solution micropore.The smaller primary dendrite arm spacing and the lower element The degree of solidification segregation makes the amount of solid solution micropores generated inside it much smaller than the HRS alloy.