Abstract The influence of the addition of filler powder on the microstructure and properties of laser-welded Ti2AlNb joints was comparatively investigated using scanning electron microscopy, transmission electron microscopy, electron back scattered diffraction, and tensile tests. The heat affected zone (HAZ) of laser-additive-welded joints was divided into B2, B2 + α2, and B2 + α2 + O — three regions with increasing distance from the fusion line. The HAZ of laser-welded joints could only be divided into two regions, viz., B2 + α2 and B2 + α2 + O. The microstructure of the fusion zone was composed of a single B2 phase for both laser welding and laser-additive welding. Columnar grains were observed in the fusion zone of laser-welded joints, while the B2 grains in the fusion zone of laser-additive-welded joints were basically equiaxed. A misorientation angle distribution analysis showed that the fraction of high-angle grain boundaries of laser-additive-welded joints was higher than that of laser-welded joints. The addition of filler powder promoted heterogeneous nucleation during solidification in laser-additive welding. Following tensile tests at room temperature, failure tended to occur in the fusion zone of the laser-welded joints and in the HAZ of the laser-additive-welded joints. The laser-additive-welded joints exhibited better tensile properties because of the higher Mo content as well as the equiaxed microstructure of the fusion zone.

中文翻译：

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激光焊接与激光增材焊接添加填料粉末制备Ti 2 AlNb接头组织和拉伸性能的对比研究

摘要 采用扫描电镜、透射电镜、电子背散射衍射和拉伸试验，对比研究了填料粉的添加对激光焊接Ti2AlNb接头组织和性能的影响。激光增材焊接接头的热影响区（HAZ）随着距熔合线距离的增加，分为B2、B2+α2和B2+α2+O三个区域。激光焊接接头的热影响区只能分为两个区域，即 B2+α2 和 B2+α2+O。熔合区的微观结构由单一的 B2 相组成，用于激光焊接和激光添加剂焊接. 激光焊接接头熔合区观察到柱状晶粒，而激光增材焊接接头熔合区B2晶粒基本为等轴晶。取向角分布分析表明，激光增材焊接接头的大角度晶界比例高于激光焊接接头。填充粉末的添加促进了激光增材焊接凝固过程中的异质形核。在室温下进行拉伸试验后，激光焊接接头的熔合区和激光增材焊接接头的热影响区往往会发生失效。由于较高的钼含量以及熔合区的等轴显微组织，激光增材焊接接头表现出更好的拉伸性能。填充粉末的添加促进了激光增材焊接凝固过程中的异质形核。在室温下进行拉伸试验后，激光焊接接头的熔合区和激光增材焊接接头的热影响区往往会发生失效。由于较高的钼含量以及熔合区的等轴显微组织，激光增材焊接接头表现出更好的拉伸性能。填充粉末的添加促进了激光增材焊接凝固过程中的异质形核。在室温下进行拉伸试验后，激光焊接接头的熔合区和激光增材焊接接头的热影响区往往会发生失效。由于较高的钼含量以及熔合区的等轴显微组织，激光增材焊接接头表现出更好的拉伸性能。