抽拉速率跃迁对定向凝固单晶高温合金DD3一次枝晶间距和微观偏析的影响

金属学报, 2009, 45(10): 1225-1231. doi: 10.3321/j.issn:0412-1961.2009.10.012

抽拉速率跃迁对定向凝固单晶高温合金DD3一次枝晶间距和微观偏析的影响

黄太文 ^1, , 刘林 ^2, , 张卫国 ^3, , 张军 ^4, , 傅恒志 ^5,

1.西北工业大学凝固技术国家重点实验室,西安,710072

2.西北工业大学凝固技术国家重点实验室,西安,710072

3.西北工业大学凝固技术国家重点实验室,西安,710072

4.西北工业大学凝固技术国家重点实验室,西安,710072

5.西北工业大学凝固技术国家重点实验室,西安,710072

基金项目: 国家重点基础研究发展规划(973计划)(2006CB605202) 国家自然科学基金(50771081和50827102)

关键词：单晶高温合金 , 生长速率 , 跃迁 , 一次间距 , 微观偏析

INFLUENCE OF WITHDRAWING RATE TRANSITION ON THE PRIMARY DENDRITE ARM SPACING AND MICROSEGREGATION OF DIRECTIONALLY SOLIDIFIED SINGLE CRYSTAL SUPERALLOY DD3

Keywords： single crystal superalloy , growth rate , transition , primary dendrite arm spacing , microsegregation

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.

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.

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