大厚度TC4钛合金超窄间隙激光填丝焊接头组织性能研究

Study on Properties and Microstructures of Large Thickness TC4 Titanium Alloy Welded Joint by Ultra-Narrow Gap Laser Welding Using Filler Wire

采用激光填丝焊接方法进行96 mm厚TC4钛合金板超窄间隙焊接,并对焊接接头进行了组织和性能分析。研究发现:焊缝整体呈钉形,没有出现气孔、裂纹及侧壁未熔合等焊接缺陷;焊缝区域主要由大量细长针状α’马氏体相互交织构成;焊接接头上中下3部分热影响区宽度、焊缝区域中α’马氏体板条宽度和位错密度呈递减趋势;焊接接头下部焊缝区域的α’马氏体晶界取向差在55°~65°的大角度晶界分布较中部和上部焊缝区域组织中略少一些;上中下3部分焊接接头中的焊缝区域显微硬度均明显高于热影响区和母材;沿壁厚方向焊接接头的抗拉强度与母材相当,焊接接头断裂位置均位于硬度值较高的焊缝处;最大局部应变出现在焊接接头下部中靠近母材的焊缝区域,局部应变值达到26.3%,而最小的局部应变值出现在焊接接头上部靠近母材的焊缝区,局部应变值约为14.5%。

TC4 titanium alloy plate with a thickness of 96 mm was joined through ultra-narrow gap laser welding using filler wire.Microstructures as well as properties of the joint were investigated.It was found that the appearance of the weld was like a nail,and welding defects including porosity,crack and incomplete fusion were not observed;weld zones in the upper,center and lower parts of the welded joint mainly consisted of a great deal of elongated acicular and interlacedα’phases;width of heat affected zones in the three parts of welded joint,width ofα’martensite laths,and dislocation density of weld zones were decreased;α’phase grain boundary misorientation was less in high-angle grain boundaries of 55°~65°in lower the part of the welded joint than that in the center and upper parts.The microhardness of the upper,middle and lower parts of the welded joint is obviously higher than that of the heat affected zone and the base metal,and the tensile strength of the welded joint is similar to that of the base metal,the fracture of the welded joint occurred at the weld with higher hardness value,and the maximum local strain appeared in the lower part of the welded joint near the base metal,the local strain reached 26.3%,while the minimum local strain appears in the upper part of the welded joint near the base metal,and The local strain is about 14.5%.