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.

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。