TC4钛合金激光焊接接头组织及耐蚀性研究

采用光纤激光器对4 mm TC4板材进行对接试验，研究了焊接接头各个区域的组织特点、硬度变化及耐蚀性差异，探究显微组织对硬度及耐蚀性的影响。研究表明，焊接接头焊缝截面形貌为T形，存在少量气孔。焊缝存在粗大的原β柱状晶，晶内组织为细小的马氏体α′相；熔合线附近观察到贯穿热影响区和焊缝的原β柱状晶；热影响区组织为等轴晶，晶内组织为马氏体α′相、少量原始α相和原始β相。焊接接头的显微硬度从母材到焊缝呈现逐渐增加的趋势，至焊缝中心达到最高，约为母材的1.78倍。焊缝显微硬度也存在差异，从焊缝顶端至焊缝底端呈现不断下降的趋势。电化学测试结果表明，焊缝的Rct值分别是母材和热影响区的4.32倍和2.58倍，且具有最高的自腐蚀电位和最小的电流密度，表征为最优耐蚀性。

Microstructure and Corrosion Resistance of TC4 Titanium Alloy Laser Welded Joints

The butt welding test of 4 mm TC4 plate was carried out by fiber laser. The microstructure characteristics, hardness changes and corrosion resistance differences of each area of welded joints were studied, and the influence of microstructure on hardness and corrosion resistance was explored. The research shows that the weld section morphology of the welded joint is T-shaped and there are a few pores. There are coarse β columnar crystals in the weld, and the microstructure is fine martensite α′ phase. β columnar crystals throughout the heat affected zone and weld are observed near the fusion line. The microstructure of the HAZ is equiaxed, and the in-grain microstructure is martensite α′ phase and a small amount of original α phases and β phases. The microhardness of the welded joint increases gradually from the base metal to the weld, and reaches the highest at the weld center, which is about 1.78 times of the base metal. There are also differences in the microhardness of the weld, which shows a decreasing trend from the top to the bottom of the weld. The electrochemical test results show that the Rct of the weld is 4.32 times of that of the base metal and 2.58 times of that of the heat affected zone, and it has the highest self-corrosion potential and the smallest current density, which characterize the optimal corrosion resistance.