Friction stir welding of steel-aluminum bimetals using a nickel-based superalloy tool

In this work, the possibility of producing steel-aluminum bimetals by friction stir welding using nickel superalloy tools was investigated. Aluminum alloy 5056 and stainless steel 304 were used as materials. Several welding techniques were investigated: with a large pin diameter tool through steel and through aluminum, and with a small pin diameter tool through aluminum. It was found that when welding through steel, the large pin quickly failed. When welding with a large pin through aluminum, it is very difficult to achieve quality joints because the distribution of the heat input is not optimal. The best joints were produced when welding by a small pin through aluminum. This resulted in a strength of 68% of the aluminum alloy strength.