焊接速度对TC4钛合金光纤激光焊接接头组织性能的影响

EFFECT OF WELDING SPEED ON MICROSTRUCTURE AND PROPERTIES OF FIBER LASER WELDED JOINT OF TC4 TITANIUM ALLOY

采用光纤激光器对4 mm厚的TC4钛合金板进行了激光焊接,通过调整焊接速度获得了不同热输入下的焊接接头,利用金相设备、显微硬度计和拉伸试验机对焊接接头的显微组织和力学性能进行研究。结果表明:焊接速度从150 mm/s降低到120 mm/s时,焊缝密集型气孔消失;当焊接速度为30 mm/s时,在焊缝中没有观察到气孔;随着焊接速度的降低,焊缝上熔宽从0.7 mm增加到2.5 mm,下熔宽从0.8 mm增加到2.8 mm。从母材到焊缝,针状马氏体α'的数量明显增加,焊缝中心产生大量马氏体α'。焊接接头的显微硬度从焊缝中心的367 HV下降到母材的344 HV;低焊接速度下,有利于气孔逃逸出熔池,断裂发生在母材。高焊接速度下,断口中有气孔产生,严重影响焊接接头强度和延伸率,使得断裂发生在焊缝。

The laser welding of 4 mm thick TC4 titanium alloy plate was carried out by using fiber laser,and the welded joints with different heat input were obtained by adjusting the welding speed.The microstructure and mechanical properties of the welded joints were studied by metallographic equipment,microhardness tester and tensile testing machine.The results show that the dense pores in the weld disappear when the welding speed decreases from 150 mm/s to 120 mm/s.When the welding speed is 30 mm/s,no pores are observed in the weld.With the decrease of welding speed,the upper weld width increases from 0.7 mm to 2.5 mm,and the lower weld width increases from 0.8 mm to 2.8 mm.From the base metal to the weld,the number of acicular martensiteα'increases obviously,and a large amount of martensiteα'is produced in the center of weld.The microhardness of welded joint decreases from 367 HV in the center of the weld to 344 HV of the base metal.At low welding speed,the pores can escape from the molten pool,and the fracture occurs in the base metal.At high welding speed,there are pores in the fracture,which seriously affect the strength and elongation of welded joint,so that the fracture occurs in the weld.