采用液态金属冷却高梯度定向凝固技术,在2~400 μm/s的抽拉速率范围内对镍基单晶高温合金DD6的凝固组织、偏析和γ/γ'共晶组织演化进行了研究.采用电子探针微区分析(EPMA)定量分析了溶质元素的微观偏析行为,讨论了溶质元素偏析及枝晶间距对共晶组织演化的影响.结果表明:随着抽拉速率增大,共晶体积分数先增多后减少.在较低的冷却速率下,固相反扩散能够减轻微观偏析,从而减少共晶体积分数,而在高的冷却速率下,固相反扩散的作用被严重削弱,枝晶间距减小对减少共晶体积分数起到了十分重要的作用.
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