Aluminium alloy battery tray / lower box of battery pack is mainly made of steel and aluminium alloy. Aluminium alloy is favored by more and more automobile OEMs and battery tray manufacturers around the world because of low destiny of battery tray bracket and various forming processes, which can meet the requirements of electric vehicle lightweight. At present, the aluminium alloy battery tray has two process schemes: integral casting and aluminium profile welding. Friction stir welding has been widely used in universal battery tray welding because of its non-melting, automation, intelligence, environment-friendly and integrated characteristics.