Friction Stir Welding Of 6005A-T6 Aluminum Alloy For The Metro Vehicles Car Body

Aluminum alloy is the preferred material for the production of metro vehicles car body. Owing to its characteristics of light weight, good corrosion resistance, good mechanical performance, etc. It is of great significance to research on friction stir welding(FSW) of aluminum alloy of the metro vehicles car body, for the FSW can overcome the shortage of the fusion welding.To obtain good welded joints of the 6005A-T6 aluminum alloy for the metro vehicle’s floor and roof, which the respectively thickness is 4mm and 2.2mm, welding with different stirring head and welding parameters, the characteristics of joining, tensile properties, bending properties, micro-structures, and fatigue strength were investigated to confirm the optimal friction stir welding process parameters. The main conclusions of this paper are as follows:(1) For the vehicle’s floor which material thickness is 4 mm, using the evolvent shoulder, shoulder diameter is 15 mm, diameter of stirring pin is 6.5 mm and length of stirring pin is 6.5 mm, under the condition of the stirring speed 1400 rpm, welding speed 600 mm/min, it acquire the joint without defect, and no crack of positive bending or negative bending the performance of bending meet the requirements, the joint has the optimal tensile strength and yield strength, the tensile strength is 216 MPa, yield strength is 135 MPa.(2) For the vehicle’s roof which material thickness is 2.2 mm, using the evolvent shoulder, shoulder diameter 11 mm, diameter of stirring pin is 4.5 mm and length of stirring pin is 4.5 mm, under the condition of the stirring speed 1500 rpm, welding speed 600 mm/min, acquire the joint without defect, and no crack of positive bending or negative bending the performance of bending meet the requirements, the joint has the optimal tensile strength and yield strength, the tensile strength is 224 MPa, yield strength is 146 MPa.(3) The fatigue test of the FSW’s joint showed that the location of the crack are the both up and down surface and profile of the sample, most of them are distributed in the area which the distances 3-7 mm range from the joint center, namely the weld heat engine affected zone and heat affected zone. Welded joint fatigue crack extension of the fracture zone exists obvious fatigue cracks, instantaneous fault zone mainly ductile fracture.