In this study, a broad range of parameter combinations (laser power: 100–400 W; scanning speed: 10–90 mm/s) were used to fabricate Ti-47Al-2Cr-2Nb alloy at the layer thickness of 100 μm by selective laser melting (SLM). The preparation of the TiAl-single track by SLM was prone not only to balling and irregularity but also to cracking. Although the optimized process parameters were used to fabricate TiAl specimens, many pores and cracks still existed and a low density was achieved. To understand the mechanism for the crack and pore formation, the connections among the cracks, pores, and the process parameters were investigated in addition to the variation in the crack propagation with an increase in the number of deposition layers. The results indicated that the cracks originated in the third layer, because of the accumulation of residual stresses and the changes in the composition of Ti-47Al-2Cr-2Nb deposition layers. Additionally, the frequency of cracks constantly increased with an increase in the number of deposition layers. Preheating the substrate to 200 °C improved the degree of cracking to a certain extent, as the initiation layer for the cracks increased from the third layer to the fifth layer. Despite the achieved improvement, it was not possible to produce crack-free specimens on the SLM machine used for this study. Finally, there was a good metallurgical bond between the Ti-6Al-4 V substrate and the Ti-47Al-2Cr-2Nb deposition layers that was free of pore and crack defects. These findings suggest that using SLM to fabricate Ti-6Al-4 V/TiAl intermetallic laminate composites may potentially eliminate cracking and improve the properties of TiAl alloys.

在这项研究中，广泛的参数组合（激光功率：100–400 W；扫描速度：10–90 mm / s）被用于通过选择性制造厚度为100μm的Ti-47Al-2Cr-2Nb合金激光熔化（SLM）。SLM对TiAl单轨的准备不仅容易产生滚珠和不规则性，而且还会产生裂纹。尽管使用了优化的工艺参数来制造TiAl样品，但仍然存在许多孔和裂纹，并且密度很低。为了理解裂纹和孔形成的机理，除了随着沉积层数的增加裂纹扩展的变化之外，还研究了裂纹，孔之间的连接以及工艺参数。结果表明，裂纹起源于第三层，由于残余应力的积累和Ti-47Al-2Cr-2Nb沉积层组成的变化。另外，随着沉积层数量的增加，裂纹的频率不断增加。将基板预热至200°C时，裂纹的起始层从第三层增加到第五层，在一定程度上改善了裂纹的程度。尽管取得了改进，但仍无法在用于本研究的SLM机器上生产无裂纹的样品。最后，在Ti-6Al-4 V衬底和Ti-47Al-2Cr-2Nb沉积层之间有良好的冶金结合，没有孔隙和裂纹缺陷。