Abstract
The ultrafine grained (UFGed) 1050 Al plates with a thickness of 2 mm, which were produced by the accumulative roll bonding technique after five cycles, were friction stir butt welded to 2 mm thick 6061-T6 Al alloy plates at a different revolutionary pitch that varied from 0.5 to 1.25 mm/rev. In the stir zone, the initial nano-sized lamellar structure of the UFGed 1050 Al alloy plate transformed into an equiaxial grain structure with a larger average grain size due to the dynamic recrystallization and subsequent grain growth. However, an equiaxial grain structure with a much smaller grain size was simultaneously formed in the 6061 Al alloy plates, together with coarsening of the precipitates. Tensile tests of the welds obtained at different welding speeds revealed that two kinds of fracture modes occurred for the specimens depending on their revolutionary pitches. The maximum tensile strength was about 110 MPa and the fractures were all located in the stir zone close to the 1050 Al side.
Highlights
As a solid state joining process, friction stir welding (FSW) was invented by the welding insituteTWI in the UK with the original purpose to weld light metals such as aluminum and magnesium alloys, which has been demonstrated to be very difficult by traditional fusion welding methods [1,2].Since FSW is performed at a temperature lower than the melting point of the materials to be welded, FSW can produce joints with fewer defects or porosity, low residual stresses, etc., compared with other fusion welding methods [3,4]
ultrafine grained (UFGed) materials have an increased length of grain boundaries acting as obstacles for moving dislocation and exhibit superior properties at ambient temperature to their coarse grained counterparts, which makes them attractive candidates for a range of potential applications in the automotive, Metals 2016, 6, 249; doi:10.3390/met6100249
The dissimilar FSW was performed between 2 mm thick UFGed 1050 Al and commercial 6061-T6 Al alloy plates
Summary
TWI in the UK with the original purpose to weld light metals such as aluminum and magnesium alloys, which has been demonstrated to be very difficult by traditional fusion welding methods [1,2]. Since FSW is performed at a temperature lower than the melting point of the materials to be welded, FSW can produce joints with fewer defects or porosity, low residual stresses, etc., compared with other fusion welding methods [3,4]. With the increasing effort to improve fuel efficiency in industry, the use of the FSW technique must be in strong demand in the near future for the welding of light materials, especially aluminum and magnesium alloys. UFGed materials have an increased length of grain boundaries acting as obstacles for moving dislocation and exhibit superior properties at ambient temperature to their coarse grained counterparts, which makes them attractive candidates for a range of potential applications in the automotive, Metals 2016, 6, 249; doi:10.3390/met6100249 www.mdpi.com/journal/metals
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