- Tayfun Soysal, The University of Wisconsin, Madison
Solidification cracking is a serious weld defect in welding Al alloys. A new test method has been developed and used to evaluate solidification cracking susceptibility of Al alloys. The test method was used with both gas tungsten arc welding (without filler metal) and gas metal arc welding (with filler metal) to make lap welds. The test results of wrought Al alloys showed that the susceptibility to solidification cracking increased in the order of 2219 Al, 2014 Al, 2024 Al, 7075 Al, and 6061 Al; that is consistent with the literature. The cracking test was also used to study the effect of filler metals on reducing susceptibility of 2024 and 6061 Al alloys to solidification cracking. Sheets of 2024 Al were welded with commercial filler metals 2319 Al, 4043 Al, and 4145 Al; 6061 Al sheets were welded with fillers 4043 Al and 4943 Al (a recently commercialized filler metal to increase weld strength). The test results showed that 4145 Al and 2319 Al are respectively the most and the least effective filler metals to reduce the crack susceptibility of 2024 Al alloy. The effects of filler metals 4043 Al and 4943 Al on reducing the crack susceptibility of 6061 Al alloy were similar. These test results were compared to the susceptibility predictions made with a recently proposed cracking index, the maximum │dT/d(fS)1/2│, where T is temperature and fS is fraction of solid, which has been used to predict crack susceptibility of Al alloys. These crack susceptibility predictions were made using the thermodynamic software Pandat based on the compositions of the 2024 and 6061 Al welds. The predictions agreed well with the test results. Micrographs and T vs. fS curves of the welds were used to explain the crack susceptibility test results.