Effect of Preheating and Dry Ice Cooling on Dissimilar Friction Stir Welding of AA7075-T6 and AZ31B

In this study, dissimilar friction stir welding behavior of AA7075-T6 aluminum and AZ31B magnesium alloys were investigated. Aluminum and magnesium alloys were joined by friction stir welding under four welding conditions and in two environments, namely pre-heated aluminum and dry ice for cooling, with tool rotation of 1120 rpm, table speed of 20 mm/min and two different tool offset values. The welding quality of the joined specimens were evaluated by employing destructive and non-destructive testing methods. The influence of the pre-heating applied to the aluminum alloy and employing ice cooling during the welding process on the mechanical and microstructural properties were examined. The test results showed that the higher tensile strength values were obtained from welded specimens of the pre-heated and cooled by dry ice during the welding process. Porosities were seen on the welded surface of the pre-heated specimen while the cavities were observed on the joint line of the cooled specimen using dry ice during the process. A homogenous material mixing was achieved in the stir zone of the welded specimens subjected to pre-heating and dry ice cooling process compared with the normal welded specimens.