Microcracks in aluminium alloys developed in the cleaning action region

Abstract

Summary Microcracks developed in the cleaning action region during the GTA (TIG) process have been investigated using aluminium and aluminium alloys. Although no microcracks are found in pure aluminium and commercially pure aluminium, microcracks are mainly developed in Al‐Mg alloys where the oxide film is ruptured by the cleaning action. The microcracking trend found is analogous to the weld solidification crack susceptibility of Al‐Mg alloys, and the microcracks developed in the cleaning action region are predicted to be related to solidification cracks. The microcracks readily develop with an increasing EN ratio of the welding current. A pattern of solidified dendrites is clearly visible, suggesting that the microcracking has developed by the cathode spot formed leading to local melting. The microcracking is also intergranular. The cooling rate during solidification can be estimated from the dendrite size, being put at around 104 °C/sec. Microcrack development is considered to be due to the fact that t...