Abstract Protection of the molten pool from gaseous contamination has always been of prime importance in welding of titanium alloys. A vacuum environment in electron beam welding serves this purpose and eliminates the use of shielding gas during the joining process. However, this may lead to variation in microstructure, mechanical properties, residual stress distribution and distortions compared to the widely used laser and TIG welding operations. In the present work, EBW was used to weld Ti-5Al-2.5Sn alloy sheet with welding current ranging from 14 mA to 20 mA. Owing to vacuum environment, oxygen contents in the fusion zone were very low for all the welding currents. However, welding current had a significant influence on the weld pool width, micro-hardness and grain size in the FZ. A complete martensitic transformation was not observed in the FZ at any of the welding currents used. Furthermore, maximum residual stresses upto 280 MPa (compressive) and 320 MPa (tensile) were found in the longitudinal direction near the weld centerline. The measured high residual stresses, distortions and partial martensitic transformations in FZ were attributed to a reduced cooling rate due to the absence of shielding gas in electron beam welding.

中文翻译：

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全熔透电子束焊接Ti-5Al-2.5Sn合金薄板组织、力学性能及残余应力研究

摘要 保护熔池免受气体污染一直是钛合金焊接的首要任务。电子束焊接中的真空环境用于此目的，并在连接过程中消除了保护气体的使用。然而，与广泛使用的激光和 TIG 焊接操作相比，这可能导致微观结构、机械性能、残余应力分布和变形的变化。在目前的工作中，EBW 用于焊接 Ti-5Al-2.5Sn 合金板，焊接电流范围为 14 mA 至 20 mA。由于真空环境，所有焊接电流的熔合区氧含量都非常低。然而，焊接电流对 FZ 中的熔池宽度、显微硬度和晶粒尺寸有显着影响。在任何使用的焊接电流下，都没有在 FZ 中观察到完整的马氏体转变。此外，在焊接中心线附近的纵向上发现了高达 280 MPa（压缩）和 320 MPa（拉伸）的最大残余应力。FZ 中测得的高残余应力、变形和部分马氏体转变归因于电子束焊接中没有保护气体导致冷却速度降低。