利用50 m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80 μm,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 ～80 μm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17 μm.
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