7 mm厚TC4钛合金电子束焊接头组织和性能

Microstructure and properties of electron beam welded joint of 7 mm thick TC4 titanium alloy

采用真空电子束焊对7 mm厚TC4钛合金板进行焊接,利用光学显微镜对焊接接头显微组织进行表征,分析不同区域显微组织,通过显微硬度、拉伸试验、冲击试验、弯曲试验对力学性能进行测试,借助扫描电镜对拉伸、冲击断口形貌进行观察,对焊接接头显微组织演变规律和性能进行研究。结果表明,真空电子束焊焊接接头成形良好,TC4钛合金母材组织由α相和β相组成,焊缝区组织由原始的β相转变而成α′相(针状马氏体),为粗大的柱状晶组织,热影响区组织由均匀且细小的针状马氏体α′相及原始的α相和β相组成;焊缝区显微硬度高于热影响区和母材区,从焊缝顶部到根部显微硬度逐渐下降;焊接接头抗拉强度高于母材抗拉强度;V形缺口在焊缝区的冲击试样具有较好的韧性。

The 7 mm thick TC4 titanium alloy plate was welded by vacuum electron beam welding.The microstructure of the welded joint was characterized by optical microscope,the microstructure composition of different areas was analyzed,the mechanical properties were studied by microhardness,tensile test,impact test and bending test,and the tensile and impact fracture morphology were observed by scanning electron microscope.The microstructure evolution and properties of the welded joint were studied.The results show that the welded joint is well formed by vacuum electron beam welding.The microstructure of TC4 titanium alloy base metal is composed ofαphase andβphase,the microstructure of weld zone is theα′phase transformed from the originalβphase,that is,the acicular martensite is composed of thick columnar crystal structure,the heat-affected zone is composed of uniform and fine acicular martensite and the originalαphase andβphase.The microhardness of weld zone is higher than that of heat-affected zone and base metal zone,and the microhardness decreases gradually from the top of weld to the root.The tensile strength of welded joint is higher than that of base metal.The impact specimen with V-notch in the weld zone has better toughness.