镍基双晶高温合金定向凝固过程中的竞争生长

金属学报

2011, Vol. 47

Issue (6): 641-648

论文

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镍基双晶高温合金定向凝固过程中的竞争生长

卢琦¹,²,李金国³,金涛²,周亦胄²,孙晓峰²,胡壮麒⁴

1.
2. 中国科学院金属研究所
3. 中科院金属研究所
4. 中国科学院金属研究所高温合金部

COMPETITIVE GROWTH IN BI-CRYSTAL OF NI-BASED SUPERALLOYS DURING DIRECTIONAL SOLIDIFICATION

引用本文:

卢琦李金国金涛周亦胄孙晓峰胡壮麒. 镍基双晶高温合金定向凝固过程中的竞争生长[J]. 金属学报, 2011, 47(6): 641-648.

全文: PDF(6177 KB)

摘要: 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都平行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。晶粒竞争生长从三个方向同时进行，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速率加快。

Abstract：Single crystal nickel-based superalloys, which offer improved creep-rupture, fatigue, oxidation and coating properties, have been widely applied in turbine blades and vanes. In general, the single crystal structure is produced through competitive grain growth by directional solidification technology. To understand the competitive grain growth mechanism during directional solidification, the bi-crystal experiment has been employed by many researchers, and several models have been proposed. Up to now, the competitive grain growth mechanism is still not clear yet, which is reflected in two areas, as shown in the follows. First, the influence of the growth rate on the competitive grain growth is not clear yet; second, the illustration of competitive grain growth are based on the two-dimensional simplified models. However, in actual directional solidification process, the orientations of the primary and secondary dendrites are random due to the randomness of the grain nucleation. Therefore, the actual competitive grain growth during directional solidification is a three-dimensional process. However the related literatures are fewer. In the present study, an experimental study has been conducted to investigate the three-dimensional competitive grain growth behavior under different withdrawal velocities by the bi-crystal samples with special orientation relationships. The results show that the whole sample with bi-crystal microstructure can be obtained when the two seeds are with the same primary dendrites orientation paralleled to the heat flow direction but different orientations of the secondary dendrites. And the withdrawal velocity has little influence on the competitive grain growth in this disposition relationship. However, only the favorably oriented grain can be obtained when the two seeds are with the non-coplanar primary dendrites and a group of secondary dendrites with the same orientation. The favorably oriented grain overgrows the misaligned grain in a heliciform way. And the overgrowth velocity is in direct proportion to the withdrawal velocity.

收稿日期: 2010-12-24

基金资助:

国家自然科学基金项目;国家重点基础研究发展计划资助;国家自然科学基金项目

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	卢琦
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	孙晓峰
	胡壮麒
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https://www.ams.org.cn/CN/Y2011/V47/I6/641

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