40mm厚TC4钛合金窄间隙激光填丝焊接头组织及性能

Microstructure and Properties of 40 mm-thick TC4 Titanium Alloy Welded Joint by Narrow-gap Laser Welding with Filler Wire

利用窄间隙激光填丝焊接工艺完成了40 mm厚TC4钛合金的焊接,通过OM、SEM、EDS、XRD、EBSD等测试方法对接头各区域进行微观组织和结构分析,并测试了其力学性能。结果表明,焊缝截面整体成形良好,无明显未熔合与气孔缺陷。接头三个区域的显微组织相同:焊缝柱状晶内部分布着密集排列的针状α′马氏体和弥散分布的颗粒状的α_(g)相,同一β晶粒内部α′择优取向,大角度晶界比例较高。焊缝中心各区都是典型的α′+β双相结构。热影响区为过渡态组织,越靠近焊缝侧,其组织形态与焊缝处越相似,焊接过程中Al元素向热影响区发生了扩散。焊接接头焊缝区整体硬度高于母材,盖面区最高,平均值约为380HV。接头的抗拉强度最大值为954 MPa,拉伸试样均断在母材,断口为韧性断裂,接头各区室温冲击性能均低于母材。

40 mm-thick TC4 titanium alloy was welded by narrow-gap laser welding with filler wire.The microstructure and structure of each area of the welded joint were analyzed by OM,SEM,EDS,XRD,EBSD and other testing methods,and the mechanical properties were tested.The results show that the weld cross section is well formed without obvious lack of fusion and pore.The microstructure of the three areas of the joint is essentially the same:there are densely arranged needleα′martensite and dispersed granular α_(g) phase in the columnar crystal of the weld,in the sameβgrain,theα′orientation is preferred and the ratio of grain boundary with large angle is higher and all the areas of the weld center haveα′+βphase structure.The heat-affected zone presents as transition-state structure.The closer it is to the weld,the more similar its microstructure is to that of the weld.In the welding process,Al element diffuses into the heat-affected zone.The overall hardness of the weld area of the welded joint is higher than that of the base metal,and the cover layer is the highest,with an average value of about 380 HV.The maximum tensile strength of the joint reaches 954 MPa.The tensile samples are all broken in the base metal with ductile fracture.The impact performance of the joints at room temperature is all lower than that of the base metal.