STUDY ON WELDING CHARACTERISTICS OF COMBINING LASER WELDING AND RESISTANCE SEAM WELDING JOINED TI-6AL-4V LAP JOINTS

摘要

Combining laser welding and resistance seam welding (LW-RSEW), lap welding of Ti-6Al-4V alloy plates with 1.4mm thickness was carried out and the welding characteristics of LW-RSEW joint were investigated. The results indicate that, compared with "V" profile of LW weld, the cross section of LW-RSEW joint is "cross" profile and the weld width at faying interface is greatly increased, which is correspond to increase the joint shear strength. The LW-RSEW joints fail in the heat affected zone (HAZ) and average tensile shear load is 21.50kN. By means of X-rays inspecting, it's found that there is almost no porosity in the LW-RSEW joints. The mechanism of porosity elimination was analysed in detail. Furthermore, metallographic examination of the joint reveals that in the nugget the microstructure is coarse beta with internally acicular morphology and the HAZ consists of a mixture of primary alpha and transformed beta with some acicular alpha. Hardness of the HAZ slightly rises compared with base metal (350HV); the hardness in the nugget is highest and the peak value reaches about 425 HV due to the structure transformation to martensite.