Improving Centerline Solidification Crack Resistivity of AA 2024 Using Tandem Side-by-Side GTAW Technique

Abstract

In this study, four gas tungsten arc welding (GTAW) techniques were employed by varying the travel speed and arc motion to analyze centerline solidification crack resistivity, namely slow (3.6\xa0mm/s), fast (8.4\xa0mm/s), weaving (4.2\xa0mm/s), and tandem side-by-side with alternating working electrodes (3.6\xa0mm/s). Welding high-strength materials like aluminum alloy 2024 (AA 2024) using fusion welding processes may cause centerline solidification cracking due to the wide range of solidification temperatures. AA 2024 was used because of its high susceptibility to centerline solidification cracking; it is mainly used in aerospace industries. This alloy is considered a nonweldable material when fusion welding processes are applied. A GTAW process was used because it has better control over the welding parameters and produces high quality welds. Overall, the tandem technique resulted in thinner axial grain structure surrounded by some equiaxed grains in the weld zone. Moreover, the resistance of centerline solidification cracking was improved by using the tandem technique because of the resulting disordered grain orientation, which reduces crack energy by deflecting the crack path and preventing crack propagation through thickness. In addition, a reduction in the average grain size of 40–60 % was achieved by implementing the tandem technique because of its fast cooling rate. The tandem technique also showed better improvement in microhardness in the weld zone compared to the other three techniques.