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利用光学显微镜观察了TC4钛合金激光焊接头的显微组织,借助扫描电子显微镜对母材及接头拉伸断口进行了分析。结果表明:靠近熔合线处焊缝晶粒为粗大的柱状晶,晶内组织为针状马氏体α′;焊缝中心晶粒为粗大的等轴晶,晶内组织以小块状α+β、大块状α、层片状魏氏组织和α′为主;近焊缝热影响区组织为α+α′的“筐篮”状组织;过渡区组织由高温β转变形成的α相+少量针状α′+原始(α+β)构成;近母材热影响区组织由高温β转变形成的α相和原始(α+β)构成;母材拉伸断裂形式属于延性断裂,接头拉伸断裂形式属于脆性断裂,具有解理断裂的特征。
The microstructure of TC4 titanium alloy laser welding head was observed by optical microscope. The tensile fracture of base metal and joint was analyzed by scanning electron microscope. The results show that the grain size of weld bead is coarse columnar crystal near the fusion line, and the microstructure is acicular martensite α ’. The center grain of the weld is coarse equiaxed grain, β, bulk α, lamellar Widmanstatches and α ’were the main ones. The heat affected zone near the weld was organized as α + α’ basket. The transition zone was formed by β transformation at high temperature (α + β). α-phase and original (α + β) formed by high-temperature β transformation in the near-heat-affected zone of the base metal. The tensile fracture of the parent material belongs to the ductile fracture , The tensile fracture of the joint belongs to the brittle fracture, which has the characteristics of cleavage and fracture.