薄板TC4钛合金TIG电弧和激光焊接接头晶粒尺寸与微观组织

对薄板TC4钛合金进行TIG电弧和激光焊接技术研究，重点分析了TIG焊接电流、焊接速度和激光输出功率对TC4钛合金焊接接头晶粒尺寸、微观组织和显微硬度的影响规律. 试验结果表明，在实现薄板TC4钛合金完全熔透的条件下，激光焊接具有更小热输入，接头焊缝区和热影响区宽度也显著降低. TIG焊接接头晶粒尺寸随热输入增加，呈现增加趋势. 随距焊缝中心位置增加，焊接接头晶粒尺寸均逐渐降低. TC4钛合金激光焊接接头焊缝区呈现魏氏组织特征，针状α'马氏体细小. 近缝热影响区组织为网篮状α'马氏体，而近母材热影响区为未转变α相和针状α'马氏体的双相组织. 随距焊缝中心位置增加，马氏体生成量逐渐减少，焊缝显微硬度值呈现降低趋势；同时相比于TIG焊接，TC4激光焊接接头具有更高的显微硬度.

Study on grain size and microstructure of TC4 titanium alloy TIG and laser welding joint

The TC4 sheet was welded by TIG and laser welding technology. The effects of TIG welding current, welding speed and laser output power on the grain size, microstructure and microhardness of TC4 titanium alloy welded joint were analyzed. The experimental results show that laser welding had a lower heat input, and the width of weld zone and heat-affected zone was significantly reduced under the condition of complete penetration of TC4 titanium alloy sheet. The grain size of TIG welded joint increased with the increase of heat input. The grain size of welded joint decreased gradually with the increase of distance from the center of weld. The laser welded joint showed the characteristics of widmanstatten structure with the finer acicular martensite α' phase. The microstructure of martensite α' near the heat-affected zone was basket shaped, while the microstructure of martensite α' near the base metal was double phase of untransformed α phase and needle shaped martensite α'. With the increase of the distance from the weld centerline, the martensite content decreased gradually, and the weld microhardness decreased. At the same time, compared with TIG welding, TC4 laser welded joint had higher microhardness.