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研究了镍基双晶高温合金定向凝固过程中的竞争生长.实验结果表明:当原始籽晶一次枝晶方向均平行于热流方向且二次枝晶取向不同时,定向凝固过程中双晶共存,但双晶的界面存在波动,抽拉速率对其影响不大.当原始籽晶一次枝晶([001])异面并保持其中一组二次枝晶取向([010])相同时,双晶竞争生长过程是一个三维竞争生长过程.晶粒竞争生长从3个方向同时进行,择优取向晶粒通过螺旋状生长方式淘汰非择优取向晶粒,双晶竞争生长过程与抽拉速率密切相关,随着抽拉速率的增加,择优取向晶粒淘汰非择优取向晶粒的速率加快.
The competition growth during the directional solidification of Ni-based dual-crystal superalloys was studied.The experimental results show that when the primary dendrites of primary seed crystals are parallel to the direction of heat flow and the secondary dendritic orientation is different, the twin crystals coexist during directional solidification, However, the interface of the twin crystals fluctuated and the pull rate had little effect on them. When the primary dendrites ([001]) and the same secondary dendrite orientation ([010]) were kept the same, The competition of crystal growth process is a three-dimensional competition growth process. The grain growth is carried out in three directions at the same time. The grains of the preferred orientation are eliminated by the helical growth pattern. The competition of twin growth is closely related to the pull rate, With the increase of drawing rate, the rate of removing non-preferentially oriented grains by preferential orientation grains is accelerated.