The formation of intermetallic compounds in aluminium alloy to copper friction-welded joints and their effect on joint efficiency

摘要

This article describes an investigation of nine types of aluminium alloy to copper friction-welded joints to determine their weldability, weld interface intermetallic compounds, and fracture modes. The results obtained may be summarised as follows. 1 Evaluation of the friction weldability of aluminium alloys to copper by joint efficiency suggests that A1050 and 5000 and 6000 series alloys have a maximum joint efficiency of more than 80 percent. However, 2000 series alloys and A7075 have a joint efficiency of less than 50 percent and should be regarded as having inferior weldability because of the difficulty of obtaining stable joint strength. That is to say, friction welding of A1050 and 5000 and 6000 series alloys to copper provides a higher joint strength than for 2000 series alloys and A7075. 2 Three types of Al-Cu intermetallic compounds are formed in the weld interface during friction welding of A1050, A2011, A2017, 6000 series alloys and A7075 to copper. High-Mg A2024 and 5000 series alloys form Al-Cu-Mg ternary intermetallic compounds in addition to these three types of Al-Cu intermetallic compounds. 3 Entrainment of intermetallic compounds and copper occurs near the weld interface of joints friction-welded under the optimum friction welding conditions. A5052 and A6061 form a uniform thin entrainment layer, whereas A1050, A2017, A5056, and A6063 show less entrainment. A2011, A2024 and A7075 with low joint efficiency show very intense entrainment, sustaining fracture in the entrainment layer and weld interface.