铸造Al-Mg-Mn合金的显微组织及力学性能

Microstructure and Tensile Properties of Al-Mg-Mn Alloy

研究了Mg含量、冷却速度、固溶处理对Al-6.8Mg-0.3Mn、Al-3.8Mg-0.3Mn两种合金力学性能的影响。结果表明,随着Mg含量提高,晶界相增多。当Mg含量提高到6.8%时,晶界出现网状组织;随着Mg含量升高,合金强度提高,塑性下降;通过砂型铸造空冷、金属型铸造空冷、金属型铸造淬火来实现不同的冷却速度,发现金属型淬火试样的金相组织中,在晶界附近没有析出网絮状或颗粒状第二相,而强度和伸长率要高于其他两种工艺。两种合金经过430℃×60h固溶处理后,合金的综合力学性能得到大幅度提高。Al-6.8Mg-0.3Mn金属型铸造空冷试样固溶后抗拉强度由280MPa提高到335MPa,伸长率由10.4%提高到20%。

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.