Microstructure, Mechanical Properties, and Crack Propagation Behavior in High-Nb TiAl Alloys by Directional Solidification
Microstructure, Mechanical Properties, and Crack Propagation Behavior in High-Nb TiAl Alloys by Directional Solidification
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DOI：
10.1007/s11661-018-4765-2
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发表时间：
2018-06
期刊：
影响因子：
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通讯作者：
Qi Wang;Ruirun Chen;X. Gong;Jingjie Guo;Yan-Qing Su;H. Ding;H. Fu
中科院分区：
文献类型：
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作者：
Qi Wang;Ruirun Chen;X. Gong;Jingjie Guo;Yan-Qing Su;H. Ding;H. Fu
采用冷坩埚定向凝固技术制备了Ti-47 Al-6 Nb-0.1C钛铝合金（Ti-47 Al-6 Nb-0.1C），输入功率为35 ~ 55 kW，抽拉速度为0.4 mm/min。结果表明：在35 ~ 55 kW输入功率范围内，定向凝固铸锭呈现β凝固特征;在40 ~ 45 kW输入功率范围内，定向凝固组织发育良好。随着输入功率的增加，片层间距减小，导致平均室温屈服强度有增加的趋势。稳态蠕变速率强烈依赖于片层间距，蠕变寿命取决于DS组织。发展完善的定向凝固合金能显著提高合金的蠕变性能，但对室温拉伸性能影响不大。此外，在测试断裂韧性后，裂纹扩展显示出层间裂纹、穿层裂纹和蠕变试验后主要沿着殖民地边界扩展的菌落间边界裂纹。
Titanium aluminide (Ti-47Al-6Nb-0.1C) alloys were prepared using a cold crucible directional solidification technique with an input power range of 35 to 55 kW under a withdrawing velocity of 0.4 mm/min. The macro/microstructure was characterized, and the mechanical properties were evaluated. The results show that the directional solidification (DS) ingots exhibitβ-solidification characteristics at an input power range of 35 to 55 kW, and a well-developed DS microstructure was acquired at an input power range of 40 and 45 kW. With the increasing input power, the lamellar spacing decreases, resulting in the increasing tendency in the average room-temperature yield strength. The steady-state creep rate strongly depends on the lamellar spacing, and the creep life depends on the DS microstructure. The well-developed DS alloy can significantly improve the creep properties but has little influence on the room-temperature tensile properties. Moreover, after testing the fracture toughness, the crack propagation showed interlamellar cracks, translamellar cracks, and intercolony boundary cracks that primarily propagated along the colony boundary after creep testing.