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利用50m长落管研究了SRR99镍基单晶高温合金在微重力与重力环境下的枝晶生长行为。采用金相显微镜观察了试样在微重力(微重力试样)和重力(重力试样)下凝固组织的差异,并利用图像分析软件测量了枝晶的一次臂和二次臂的长度及间距。结果表明,微重力试样在下落过程中从未熔部分外延生长的最大长度约为1.7mm,重力试样的最大长度为1.9mm。微重力试样的一次枝晶干粗大,平均间距约为80μm,而重力试样中存在较多的细小一次枝晶干,一次臂平均间距约为71μm。一次枝晶平均间距在微重力环境下增大20%。微重力试样的二次臂长度较长,且在20～160μm的整个长度范围内较均匀分布;重力试样二次臂长度较短,且集中分布在20～80μm区间内。微重力试样和重力试样的二次枝晶臂平均间距相同,均为17μm。
The dendrite growth behavior of SRR99 nickel base single crystal superalloy under microgravity and gravitation conditions was studied by using a 50m long drop tube. The microstructure of the samples was observed by optical microscopy under microgravity (microgravity) and gravity (gravity), and the length and pitch of primary and secondary arms of dendrite were measured by image analysis software . The results show that the maximum length of the microgravity sample during the ascent from the unmelted part is about 1.7mm and the maximum length of the gravity specimen is 1.9mm. The primary dendrites in the microgravity samples are coarse and dry, with an average spacing of about 80 μm. However, there are many small primary dendrites in the gravity samples with an average distance of about 71 μm. The average dendrite spacing increased by 20% under microgravity. The length of the secondary arm of the microgravity specimen is longer and uniformly distributed over the entire length of 20 ~ 160μm. The length of the secondary arm of the gravity specimen is shorter and concentrated in the interval of 20 ~ 80μm. The average distance between the secondary dendrites of the microgravity sample and the gravity sample was the same, both 17μm.