Characteristics and formation mechanism of sidewall pores in NG-GMAW of 5083 Al-alloy

Narrow-gap gas metal are welding was carried out on thick plate of 5083 Al-alloy, and the characteristics of welding pores were analyzed in terms of their size and distribution. The large pores were found to occur frequently in the weld zone adjacent to the sidewalls of narrow gap groove. Their amount and size increased along with increasing welding current and/or decreasing travel speed, which was totally different from conventional GMAW of aluminum alloy. The hydrogen was found to be the main cause to the pores by using SEM and EDS analysis. The formation of sidewall pores in narrow-gap weld beads were greatly related to the groove type, the shape of molten pool and its solidification behavior, and it was verified by polarization observation and EBSD analysis. The optimized parameters for avoiding sidewall pores and lack of sidewall fusion were 175 A and 5 mm/s in the narrow-gap welding of given aluminum alloy. (C) 2016 Elsevier B.V. All rights reserved.