Effects of Mg content

cooling rate and solution treatment on the tensile properties of Al-6.8Mg-0.3Mn

Al-3.8Mg-0.3Mn alloy were investigated.The results show that the amount of grain boundary phases is increased with increasing in Mg content

and with 6.8% Mg content

network structure occurs in grain boundary.In addition

strength is improved and the plasticity of the magnesium alloy is decreased with the Mg content increases.Mg alloy samples were fabricated in sand casting with air-cooled

metal mold casting with air-cooled

metal mold casting quenched in water to achieve different cooling rates

respectively.The results reveal that absence of flocculent or granular precipitation in the grain boundary of microstructure in quenched sample can be observed

and the strength and elongation are higher than those of the samples fabricated in the other two cooling rates.After 430 ℃ for 60 h solution treatment

comprehensive properties of the two alloys have been substantially improved.Tensile strength and elongation of Al-6.8Mg-0.3Mn alloy in permanent mold casting with air cooled are improved from 280 MPa to 335 MPa and from 10.4% to 20%

respectively

after solid solution treatment.