锂添加对Mg-6Al-2Sn-0.4Mn合金显微组织和力学性能的影响

摘要

Effects of Li addition (2%, 5%, 8% and 11%) on microstructure and mechanical properties of the as-cast and as-extruded Mg−6Al−2Sn−0.4Mn-based alloys were investigated. Mg−xLi−6Al−2Sn−0.4Mn (x= 2, 5, 8 and 11, mass fraction, %) alloys were cast under an SF6 and CO2 atmosphere at 700 °C. After homogenization heat treatment at 350 °C, cast billets were extruded with a reduction ratio of 40:1 at 200 °C. Li addition to Mg−6Al−2Sn−0.4Mn resulted in the formation of MgSnLi2 and MgAlLi2 and/or AlLi intermetallic compounds and random basal texture. With increasing Li addition,β-Li phase was increased and the average area fraction of precipitates increased. Compression yield strength was increased from 212 to 235, 242 and 239 MPa as Li content was increased from 2% to 5%, 8% and 11%, respectively. Elongation was remarkably increased above 60% in 11% Li alloy. It is probable that Li-containing phases play a significant role in the enhanced mechanical properties by Li addition.%研究添加2%、5%、8%和11%锂对铸态和挤压态Mg−6Al−2Sn−0.4Mn合金的显微组织和力学性能的影响。在SF6和CO2气氛和700°C温度下铸造Mg−xLi−6Al−2Sn−0.4Mn(x=2，5，8和11质量分数，%)合金。经350°C均匀化热处理后，铸锭在200°C进行挤压，挤压比为40：1。在Mg−6Al−2Sn−0.4Mn合金中添加锂可以形成MgSnLi2，MgAlLi2和/或AlLi金属间化合物以及随机基面织构。随着锂含量的增加，β-Li相增加且沉淀相的平均面积分数也增加。随着锂含量从2%增加至5%、8%和11%，合金的抗压屈服强度从212 MPa分别增加至235、242和239 MPa。当锂含量达到11%时，合金的伸长率超过60%。锂添加对含锂相合金力学性能的提高起到重要作用。