Research On Laser Hybrid Welding On Microstructure And Mechanical Properties Of 6N01 Aluminum Welding Joints

Aluminum alloy in railway transportation especially more and more wide application of rail vehicles, 6N01 aluminum alloy as the main material of China’s high-speed train body, has the advantages of light weight, high strength and long service life etc., but have some inconvenience to the welding, especially for the welding method of welding a reasonable choice of the more is imminent. In this paper, the different welding method(MIG welding, laser monofilament hybrid welding, laser double wire hybrid welding) of 6N01 aluminum alloy 3mm sheet thickness butt welding, through nondestructive testing, tensile test, bending test, microhardness test, metallographic test and fatigue test of welding test plate, a comprehensive evaluation method of welding effect on the microstructure and properties of 6N01 aluminum alloy butt joints of different, choose the reasonable welding method.Different welding 6N01 aluminum alloy butt joint method under all excellent weld, Xray flaw detection test were B grade, and bending test of all the joints are qualified, specimen bending angle reached 180 degrees, the specimens are all no cracks. The tensile strength of butt joints under the three kinds of welding methods are up to standard, the tensile strength of laser welding and the yield strength of the composites was obviously higher than that of other two kinds of welding methods, cross-section shrinkage and elongation is lower than that of other two kinds of welding method, laser composite double wire welding section shrinkage is far higher than other two kinds of welding methods. Three methods of welding, butt joints are softening, softening zone MIG welding is widest, softening zone laser monofilament hybrid welding and laser double wire hybrid welding is similar, but the degree of softening laser composite double wire welding is more serious.6N01 aluminum alloy base metal microstructure along the rolling direction in grain for extended fibrous, alpha(Al) matrix on the distribution of precipitation in the process of aging Mg2 Si strengthening phase; three welding methods morphology weld area was mainly under the dendrite structure, and has the Mg2 Si phase precipitated in the organization. Laser monofilament hybrid weldingand laser double wire hybrid welding due to heat input quantity is big, makes the grain in weld zone grain size is larger than during MIG welding; heat affected zone microstructure are all along the rolling direction extension is grain fibrous, and the alpha(Al) matrix on the distribution of precipitation during the aging process of Mg2 Si strengthening phase in addition, the precipitated phase increased, little change in the fusion zone morphology; no obvious columnar crystal.In the specified service life is 1×107 cycles under different welding methods, docking of 6N01 aluminum alloy joint(to remove residual high fatigue) performance of the more obvious effects. MIG welding of aluminum alloy 6N01 butt joint fatigue performance of minimum, fatigue properties of laser monofilament hybrid welding and laser double wire hybrid welding of 6N01 aluminum alloy butt joint of composite monofilaments relative MIG welding is higher, but because the welding joint by laser compound double wire softening phenomenon is more serious, so laser composite single wire welding fatigue performance is excellent.6N01 aluminum alloy 3mm sheet thickness were welded by laser monofilament hybrid welding, welding butt joint microstructure and properties of the relative MIG welding and laser double wire hybrid welding is better.