采用电子探针对不同Ｎｂ，Ｔｉ含量的Ｊ－９０合金凝固组织中Ｎｂ，Ｔｉ的面分布及枝干心部元素的化学成分进行了分析。结果表明：随合金中Ｎｂ含量增加，合金中Ｎｂ的偏析趋于严重。而Ｔｉ的分布则趋于均匀化；合金中Ｔｉ量增加时，Ｎｂ，Ｔｉ的偏析均趋于减轻。定量测试发现，当合金中Ｎｂ，Ｔｉ含量增加时，Ｎｂ，Ｔｉ的初凝平衡分配系数均有所增加。通过分析比较还发现，以元素最高含量与最低含量之差作为比较参数，可以合理地反映出合金中元素含量少量调整时元素偏析程度的变化取决于合金中元素的含量和元素分配系数这两个基本因素。同时，实验结果还说明，可以通过降低合金中微量元素含量使凝固时溶质富集层中Ｐ等微量元素含量的降低，使得Ｎｂ，Ｔｉ等易偏析元素的含量相对增加，从而使合金的凝固偏析得以降低。
EMPA has been performed to investigate the distribution of Nb and Ti in the solidification structure of J-90 alloys with different contents of Nb and Ti. With increasing of Nb content in the alloy, Nb tends to be seriously segregated, while distribution of Ti becomes more and more homogeneous, but when the content of Ti in the alloy being increased, segregations of Nb and Ti are all lessened. By increasing contents of Nb and Ti in the alloy, partition coefficients of Nb and Ti at the beginning of solidification are all increased. It was found by comparison that difference between the highest and the lowest content of an element after solidification is a more proper parameter for description of elemental segregation which is dependent on the content of elements and the elemental partition coefficient. The fact that k_(Nb) and k_(Ti) increased with increasing of Nb and Ti contents in the alloys indicated that when contents of trace elements (such as P etc.) were lowered, on the solute-rich layer during solidification there would be less these trace elements while contents of easy-segregated elements, such as Nb and Ti, could increased. As a consequence, k_(Nb) and k_(Ti) would increase and micro-segregation of Nb and Ti would decrease.
参考文献
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