Microstructures and mechanical properties of 30 mm thick titanium alloy TC4 welded joint by narrow gap TIG welding
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摘要: 对30 mm厚钛合金TC4板材进行磁控电弧窄间隙TIG焊接试验，并对其接头组织与力学性能进行检测分析，包括金相组织、拉伸强度、冲击韧性及显微硬度。通过优化焊接工艺试验，得到了外观成形美观、保护效果良好，未见宏观缺陷的窄间隙焊接接头。焊缝显微组织主要由片状α相、β相及细针状马氏体α'相组成。磁控电弧窄间隙TIG焊接中电弧在窄间隙坡口中进行周期性摆动，能够降低焊接热输入的同时保证侧壁充分熔合，得到的热影响区与常规TIG焊接方法相比要窄，宽度大约为1～2 mm。对接头进行拉伸试验，断裂位置均在焊缝处，断裂方式为韧性断裂，接头抗拉强度可达到母材的96%以上。接头热影响区硬度值最高，焊缝中心区显微硬度最低，整个接头的硬度峰值出现在热影响区的粗晶区，但未见明显的硬化及软化区域。Abstract: Narrow-gap TIG welding of the 30 mm thick titanium alloy TC4 plates was carried out,and microstructures and mechanical properties of the joint were analyzed,including metallographic microstructure,tensile strength,impact toughness and micro hardness.Through optimizing the welding process test,the appearance and the protection effect are good,the narrow gap welded joints are obtained with free of macroscopic defects.The microstructure of the weld is mainly composed of lamellarαphase,βphase and fine needle martensiticα’.The arc of the narrow clearance in TIG welding of magnetic controlled arc is oscillating periodically in narrow gap slope,which can reduce the welding heat input while guaranteeing the full fusion of the side wall,the resulting thermal influence zone is narrower than in the conventional TIG welding method,and the width is about 1-2 mm.In the tensile test of the joints,the fracture position is in the weld seam,the fracture mode is ductile fracture,the joint tensile strength can reach up to 96% of that of the parent material.The hardness of heat affected zone is the highest,that of the weld is the lowest,the hardness peak of the whole joints appears in the coarse grain zone of the HAZ,but no obvious hardening and softening zone were found.
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