Friction welding of aluminum alloy applied positioning control process

Friction welding is one of solid-state welding processes that use friction heating to join members. Aluminum alloy is preferable performances by their high specific strength, however aluminum alloy seems to be difficulties to assemble by fusion welding processes. Friction welding process is a superior characteristics on mechanical properties and on production performances, however this process is limited to apply joining of round bar materials due to lack of positioning control capability. Positioning control means controlling the stopping position of main rotating spindle when the joining was completed. This process limitation has been overcome introducing recent servo systems. This study is carried out to clarify effect of process parameters on mechanical properties of positioning controlled joints of aluminum alloy, A6061 in case of square cross section. In addition, the effect of geometry is revealed on friction welding in comparison with ordinary round bar. Two type specimens are prepaired in this study. One is square sectional bar of 17mm on a side. Other is ordinary round bar of 19mm in diameter. Cross sectional area of two type specimens are almost equivalent. In the result, Positioning control process is successfully performed, and mechanical properties are almost equivalent to conventional friction welding process when sufficient upset distance is applied. It seems to yield imperfection at the corner of square joints when the small upset distance. Higher upset load and longer friction time make a sufficient contact area in weld interface resulting in larger upset distance eliminating weld imperfection. Width of softened zones in both sections, square and round, is almost equivalent under the optimized parameters.