Investigation on softening of welded joint of side walls of high speed train of 6N01 aluminum alloy

In this paper, the softening of welded joint of 6N01 Al alloy of the side wall of high speed train welded with laser-MIG hybrid welding was investigated. The strength, hardness, microstructure of welded joint, fracture of tensile specimen, and chemical composition of weld metal were systematically investigated by means of tensile test, hardness test, metallographic test, and SEM test. All of them were compared with the MIG welding. The result showed that the strength of hybrid welding has increased by 10% compared with that of MIG welding, and decreased by 40% to 60%, but has more and fine major strengthening phase in the weld metal. So the welded joint softening of high-speed train body side wall can be improved greatly by using laser-arc hybrid welding.