Humid Gas Stress Corrosion Cracking in MIG-Welded 5083 Aluminum Alloy Plate

In 5000 series (Al-Mg) alloys, hydrogen embrittlement (HE) becomes a concern when Mg content exceeds 5%. The local Mg content will become higher than 5% due to solidification segregation in the weld joint of 5083 alloy. In this study, resistance to HE of MIG-welded 5083 aluminum alloy at three areas (weld center, weld corner and HAZ) was investigated by newly developed humid gas stress corrosion cracking (HG-SCC) test. Slow strain rate tensile (SSRT) test on base metal and welded joint was also conducted for comparison. It was newly revealed that HG-SCC crack extends only in the sample of weld corner, confirming HE in this area. For the other areas, HG-SCC crack did not propagate, confirming HE resistance of these areas. From the results of SSRT test, neither the base nor welding material showed reduction in strength or ductility. Therefore, it was concluded that HE in 5083 MIG welds is only detectable by HG-SCC test. The reason for this should be in the fact that HG-SCC test can specifically test different local areas, while the softest area (weld center) always deforms preferentially and fractures in SSRT test.