压力对A380铝合金的铸造组织和力学性能的影响

Effect of pressures on macro-/microstructures and mechanical properties of A380 aluminum alloy

对A380铝合金进行了挤压铸造成型和传统重力铸造成型,并制得试样.采用偏光显微镜、扫描电镜、定量金相分析、拉伸性能测试等手段,研究在不同压力下挤压铸造A380铝合金的铸造组织和力学性能.结果表明:当压力在0~75 MPa范围内时,随着压力的增加,一次枝晶臂尺寸和气孔率得到大幅下降,共晶组织体积分数增加;二次枝晶臂间距减小;针状富铁β-Al_5FeSi相尺寸大幅度减小,同时有部分汉字状α-Al8(Fe,Mn)_3Si_2相生成.当压力在75~100 MPa范围内时,压力继续增加对合金组织细化、第二相形貌改善和力学性能提高的作用不明显.挤压铸造试件与重力铸造试件相比,气孔率减小,显微组织细化,力学性能显著提高.当压力为75 MPa时,挤压铸造A380铝合金的铸态抗拉强度和伸长率分别比重力铸造提高19%和65%.

This study investigated the microstructures and the mechanical properties of the A380 alloy solidified at different squeeze pressures by polarizing microscopy,scanning electron microscopy,image analysis,and tensile test.The obtained results show that the microstructures of the squeeze casting specimens are much finer than those of gravity casting specimens.Moreover,the porosity and the mechanical properties of the squeeze casting specimens are remarkably improved compared with those of the gravity casting specimens.The size of the dendrite arm and the porosity decrease when the squeeze pressure is increased from 0 MPa to 75 MPa in the squeeze casting process.The eutectic volume fraction of the specimen increases,while the secondary dendrite spacing decreases.The size of the needle-like β-Al5FeSi phase significantly decreases.In addition,a few α-Al8（Fe,Mn）3Si2 phases with Chinese characters are observed in the grain boundary.The influence of the pressure on the microstructures,second-phase morphology,and mechanical properties of the squeeze casting specimens does not significantly improve with the increasing squeeze pressure when the squeeze pressure is larger than 75 MPa.The tensile strength and the elongation of the A380 alloy when the squeeze pressure is 75 MPa increase by 19% and 65%,respectively,compared with those of the gravity casting specimens.