Influence of gibbosity on recrystallization behavior of single crystal blade casting
Influence of gibbosity on recrystallization behavior of single crystal blade casting
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DOI：
10.1016/j.jmatprotec.2018.04.036
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发表时间：
2018-09
影响因子：
6.3
通讯作者：
Run-nan Wang;Qingyan Xu;Xianglin Su;Zhonglin Li;Baicheng Liu
中科院分区：
文献类型：
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作者：
Run-nan Wang;Qingyan Xu;Xianglin Su;Zhonglin Li;Baicheng Liu
针对单晶(SX)叶片铸件，采用实验和模拟相结合的方法，研究了由铂针销诱导产生的再结晶缺陷。再结晶发生在80个三棱柱中的39个，并能穿透250 μm以上的SX叶片。叶片上部、中部和下部凸起的RX出现率分别为83%、50%和8%，表明RX对凸起的位置高度具有很强的敏感性。铸态组织为SX，在凸度的横截面上没有出现微观错向晶。在RX和SX晶界存在二次碳化物颗粒。背散射电子(BE)和电子背散射衍射(EBSD)的复合图像表明，粗大的共晶粒子阻碍了RX界面的迁移。建立了考虑SX高温合金各向异性力学性能的热弹塑性模型，并与有限元方法相耦合，对定向凝固过程中的变形行为进行了预测。有限元计算结果表明，等效塑性应变(PEEQ)有集中在凸起的趋势，这为RX的形成提供了合理可靠的解释。
Recrystallization (RX) defects formed in the gibbosities induced by platinum chaplet pins were studied by experiments and simulations for single crystal (SX) blade castings. Recrystallization occurs in 39 of the 80 gibbosities and can penetrate more than 250 μm into the SX blade. The RX occurrence ratios for the gibbosities in the upper, middle and lower positions of the blade are 83%, 50%, and 8% respectively, indicating a strong sensitivity of RX to the location height of the gibbosity. The microstructure is SX without the presence of micro misoriented grains in the cross-section of gibbosity of as-cast sample. Secondary carbide particles are found at the interface between the RX and SX grains. A composite image of backscattered electron (BE) and electron backscatter diffraction (EBSD) shows that the migration of the RX interface is hindered by coarse eutectic particles. A thermal elastoplastic model that considers the anisotropic mechanical properties of SX superalloys and is coupled with a finite-element method (FEM) was utilized to predict the deformation behavior during directional solidification. The FEM results reveal that the equivalent plastic strain (PEEQ) tends to concentrate in the gibbosities, and this gives a reasonable and reliable explanation for RX formation.