CAJ | 학술논문

采用液态金属冷却高温度梯度定向凝固设备,研究了抽拉速率跃迁对单晶高温合金DD3一次枝晶间距和微观偏析的影响.结果表明,单晶高温合金枝晶一次间距表现出明显的历史相关性.当抽拉速率(或生长速率)分别从600和300 μm/s跃迁到100 μm/s和直接以100 μm/s速率生长时,一次间距分别为56.5,86和111.5 μm.而生长速率分别从50和100 μm/s跃迁到300 μm/s和直接以300 μm/s速率生长获得的一次间距分别为109,93和70 μm.一次间距值与Hunt-Lu模型预测的基本吻合,但实验结果证明其上限与下限的比值λ~(max)_1/λ~(min)_1>2,与Ma-Sahm的预测结果一致.成分分析表明,相同稳态条件下枝晶的一次间距变小,偏析也有所降低.
채용액태금속냉각고온도제도정향응고설비,연구료추랍속솔약천대단정고온합금DD3일차지정간거화미관편석적영향.결과표명,단정고온합금지정일차간거표현출명현적역사상관성.당추랍속솔(혹생장속솔)분별종600화300 μm/s약천도100 μm/s화직접이100 μm/s속솔생장시,일차간거분별위56.5,86화111.5 μm.이생장속솔분별종50화100 μm/s약천도300 μm/s화직접이300 μm/s속솔생장획득적일차간거분별위109,93화70 μm.일차간거치여Hunt-Lu모형예측적기본문합,단실험결과증명기상한여하한적비치λ~(max)_1/λ~(min)_1>2,여Ma-Sahm적예측결과일치.성분분석표명,상동은태조건하지정적일차간거변소,편석야유소강저.
contrast, PDASs increase to 109 and 93 μm under withdrawing rate transition from lower values of 50 and 100 μm/s into 300 μm/s, while they are kept being a small value of 70 μm if growth rate is 300 μm/s at beginning. These experimental results agree approximately with those from Hunt-Lu model, but the maximum to minimum ratio of PDASs at a given solidification parameter, i.e., λ~(max)_1/λ~(min)_1, is proved to be more than 2. It is also shown that the dendrite microsegregation will be lessened with the decrease of PDASs at the same current solidification parameters.