Study on Laser Welding Technology of TA5 Titanium Alloy with Filler Wire
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摘要: 采用激光填丝焊,实现了4 mm厚TA5钛合金I型坡口单道焊双面成型,研究了工艺参数对焊缝成型、气孔率和力学性能的影响,结果表明,焊缝成型美观,抗拉强度最高可达797.5 MPa,为母材的98.2%。激光功率增加,背面焊透量增加,焊缝气孔率先降低后增加,抗拉强度增加;离焦量由负离焦增加到正离焦时,焊缝的咬边缺陷消失,气孔率呈先增后降的趋势,抗拉强度增加;随着焊接速度的增加,背面焊透量降低,气孔率降低,抗拉强度略微降低。金相分析结果显示,焊接时焊缝区完全发生α→β转变,而焊后冷却速度较快,导致焊缝区在冷却过程中生成了大量的针状α′相;热影响区部分发生α→β,主要是由块状α相和锯齿状α相组成。硬度测试结果显示,焊缝中心硬度较高,母材区硬度最低,近母材热影响区到母材方向的硬度出现明显的降低;焊缝顶部的硬度值高于焊缝中心和底部的。Abstract: Laser welding with filler wire is adopted to realize single pass welding and double-sided forming of 4 mm thick TA5 titanium alloy with I-groove, and welding parameters on weld formation, porosity and mechanical properties are studied.Resultsshow that the welding seam is in good shape, and that the tensile strength can reach 797.5 MPa, 98.2% of that of the base metal. With the increase of laser power, the back penetration increases, the weld porosity first decreases and then increases, and the tensile strength increases. When the defocusing amount increases from negative defocusing to positive defocusing, the undercut defects disappear, the porosity first increases and then decreases, and the tensile strength increases. With the increase of welding speed, the back penetration, porosity and tensile strength decrease slightly. The results of metallographic analysis show that in weld zone, α phase has transformed to β phase completely, The rapid cooling rate after welding results in a large number of needle like α′ phase formed in weld zone during the cooling process. In heat affected zone, α phase has partially transformed to β phase was partially destroyed which is mainly made up of bulk α phase and zigzag α phase. The hardness test shows that the hardness of the weld center is the highest, that the hardness of the base metal is the lowest, meaning the hardness from the heat affected zone to the base metal zone decrease. The hardness at the top of the weld is higher than those at the center and the bottom of the weld.
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