In this paper, the lamellar orientation control and mechanical properties of directionally solidified (DS) Ti-49Al (at%) alloy in oxide ceramic crucible were investigated. Based on the nucleation undercooling theory, the feasible solidification parameters for the lamellar orientation control of Ti-49Al (at%) alloy by the seeding technology were selected. The optimal solidification parameters were as follows: the growth rate (V) ranged from 10 to 25 μm/s, and temperature gradient (G) ranged from 10 to 20 K/mm. DS Ti-49Al (at%) alloy with paralleled lamellar orientation was successfully prepared according to the predication solidification parameters. The mechanical properties of DS Ti-49Al (at%) varied with the orientation of the lamellar structures. The specimen with paralleled lamellar orientation showed relatively higher tensile strength (450 MPa) and elongation (0.60%). The mechanical properties of specimens with paralleled lamellar orientation were greater than the specimens with equiaxed grain structures even though the specimens contaminated slightly by the interfacial reaction between the TiAl melt and the oxide ceramics crucible. Meanwhile, the fracture modes of DS Ti-49Al (at%) alloy were interlamellar mode, translamellar mode, or combined with the two modes, which also depended on the lamellar orientations.

Graphical abstract

中文翻译：

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定向凝固二元Ti-49Al合金在氧化物陶瓷坩埚中的片晶取向控制及力学性能

本文研究了定向凝固 (DS) Ti-49Al (at%) 合金在氧化物陶瓷坩埚中的层状取向控制和力学性能。基于成核过冷理论，选择了通过晶种控制Ti-49Al（at％）合金的层状取向的可行凝固参数。最佳凝固参数为：生长速率（V）范围为 10 至 25 μm/s，温度梯度（G) 范围从 10 到 20 K/mm。根据预测凝固参数成功制备了平行层状取向的DS Ti-49Al (at%)合金。DS Ti-49Al (at%) 的机械性能随层状结构的取向而变化。平行层状取向的试样表现出相对较高的拉伸强度 (450 MPa) 和伸长率 (0.60%)。尽管 TiAl 熔体与氧化物陶瓷坩埚之间的界面反应轻微污染了试样，但平行层状取向试样的机械性能优于具有等轴晶粒结构的试样。同时，DS Ti-49Al (at%)合金的断裂模式为层间模式、跨层模式或两种模式的组合，这也取决于层状取向。

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