Microstructures and Properties of Extruded Al-0.6Mg-0.6Si Aluminium Alloy for High-speed Vehicle

The Al-0.6Mg-0.6Si aluminium alloy was extruded for high-speed vehicle. The microstructure and mechanical property of extruded Al-0.6Mg-0.6Si aluminium alloy were investigated. The results of experimentation show that the tensile strength of extruded Al-0.6Mg-0.6Si aluminum alloy is above of 245 MPa, and the percentage elongation after fracture is better than 8%. The microstructure is rolling structure, and the coarse second phases distribute in α-Al solid solution matrix structure. The second phases are inclusions, coarse stable phases of β′ (Mg2Si) or their collection. The tiny β′ (Mg2Si) strengthening precipitation phases mostly distribute in the grain boundary. The size of β′ strengthening phase is about 5 nm. The width of no precipitation band is above of 50 nm. The fatigue life is 1.061×105 cycle when σmax=0.75σb. The fatigue cracks initiate in surface of extruded Al-0.6Mg-0.6Si aluminium alloy sample. The fatigue fracture is composed of the initiation zone, the propagation zone, and the sudden fracture zone, which is characteristic of a mixed-type fatigue fracture.