Microstructure and mechanical properties of twin-roll cast Mg-6Zn-1Mn-1Al alloy joined by surface-friction welding

We report that twin-roll cast and subsequently heat-treated Mg-6Zn-1Mn-1Al alloy sheets with a thin thickness of 1 mm were successfully joined by surface-friction welding process. The welded sheet revealed several distinct weld zones, which are closely related to plastic flow and frictional heat generation during welding. Although large microstructural differences were found among the welded zones, the presence of thermally stable Al8Mn5 particles pre-existing in the sheet appeared uninfluenced by the welding process. The role of the microstructural changes induced by the welding process in the hardness variation and tensile properties of the welded sheet is discussed.