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Metastable phase and microstructural degradation of a TiAl alloy produced via selective electron beam melting
Vacuum ( IF 3.8 ) Pub Date : 2021-07-27 , DOI: 10.1016/j.vacuum.2021.110491
Hangyu Yue 1 , Hui Peng 2, 3 , Ruifeng Li 1 , Jixin Yang 4 , Runqi Gao 2, 3 , Shuzhi Zhang 5 , Xiaopeng Wang 4 , Yuyong Chen 4
Affiliation  

Selective electron beam melting (SEBM) is an attractive rapid prototyping technology to fabricate TiAl alloys with a complex structure. A near fully dense Ti–47Al–2Cr–2Nb alloy was fabricated by SEBM by using a low-energy density of 20.04 J/mm3. The phase transformation, microstructural degradation and microhardness of the SEBM-produced TiAl alloy were investigated. The results showed that the microstructure was inhomogeneous along the building direction. Multiple phase transformations were observed during the in-situ thermal cycle. Disordered α phase was observed in the last solidifying tracks in the top surface due to the rapid cooling rate. A metastable Ti2Al phase was observed due to the relatively high residual stress that was caused by a quick cooling rate when fabrication occurred under a low energy density of 20.04 J/mm3. The decomposition of α2 lamellae, continuous coarsening and discontinuous coarsening of lamellar structure were the three main routes for microstructural degradation for SEBM-produced TiAl alloys. The microhardness exhibited an increasing tendency from a height of 18 mm to the top surface due to the increasing content of the lamellar colony. Finally, the degradation mechanism of the lamellar colony was discussed in detail.



中文翻译:

选择性电子束熔化制备 TiAl 合金的亚稳相和显微组织退化

选择性电子束熔化 (SEBM) 是一种极具吸引力的快速成型技术,可用于制造具有复杂结构的 TiAl 合金。通过使用 20.04 J/mm 3的低能量密度,通过 SEBM 制造了一种接近完全致密的 Ti-47Al-2Cr-2Nb 合金。研究了 SEBM 制备的 TiAl 合金的相变、显微组织退化和显微硬度。结果表明,沿建筑方向的微观结构是不均匀的。在原位热循环期间观察到多个相变。由于快速冷却速度,在顶部表面的最后凝固轨迹中观察到无序的 α 相。亚稳态 Ti 2由于在 20.04 J/mm 3的低能量密度下进行制造时快速冷却速度导致相对较高的残余应力,因此观察到 Al 相。α 2片晶的分解、片状结构的连续粗化和不连续粗化是SEBM制备的TiAl合金显微组织退化的三个主要途径。由于层状菌落含量的增加,显微硬度从 18 mm 高度向顶面呈增加趋势。最后,详细讨论了层状菌落的降解机制。

更新日期:2021-07-28
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