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| Narrow-gap|TC4 titanium alloy|Laser welding|Microstructure|Microhardness |
| WANG Xiangyu, GONG Shuili, YANG Jing, LU Wei, SHAN Feihu |
(Science and Technology on Power Beam Processes Laboratory, AVIC Beijing Aeronautical Manufacturing Technology
Research Institute, Beijing 100024, China) |
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Abstract The IPG YLS-5000 multi-mode fiber laser is used for the 12mm thick TC4 plate by the multiple-pass
narrow-gap approach. Optimized process parameters are attained, as well as the microstructure in laser beam welds of TC4
titanium alloy is investigated. The result shows that incomplete fusion and porosity could be reduced using the optimized
welding parameters. The microstructure of the base metal (BM) is typical equiaxed structure. The microstructure of fusion
zone (FZ) is composed of β columnar crystal and basket weave martensite α′ phase. The grain size of heat affected zone
(HAZ) is obviously refined. The HAZ partially transformed is made up of martensite α′ phase, transformed α and transformed
β. Moreover, the microhardness of weld metal and heat affected zone is higher than that of base metal, and the hardness
reaches to peak value in the heat affect zone near weld metal.
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2016, 
