凝固压力对Al-4.4Cu-1.5Mg-0.4La合金组织及性能的影响

Effect of Solidification Pressure on Microstructures and Mechanical Properties of Al-4.4Cu-1.5Mg-0.4La Alloy

采用凝固过程加压工艺,研究了凝固压力对Al-4.4Cu-1.5Mg-0.4La合金组织与性能的影响。结果表明,随着压力的升高,合金中的缩松等铸造缺陷逐渐减少,微观组织由树枝晶转变为等轴晶,晶粒得到细化,合金的综合性能得到显著提高;压力增加使合金中的Cu、Mg、La元素在晶粒内固溶度提高,合金元素在晶界处的偏聚得到改善,晶界中形成的S相和θ相减少,含La的脆性相比例升高,合金元素在合金中的分布更加均匀。当压力继续升高至120 MPa时,抗拉强度继续提高但伸长率反而有所下降。当压力为80 MPa时,该合金的抗拉强度为217.23 MPa,伸长率为10.61%。

The microstructures and mechanical properties of the squeeze casting Al-4.4Cu-1.5Mg-0.4La alloy under different solidification pressures were investigated. The results show that with the increase of pressure applied during solidification, the dispersed shrinkage in the alloy disappears gradually, the microstructure of the alloy transforms from the dendritic to the equiaxial crystals and is refined effectively, the mechanical properties of the alloy are improved greatly. With increasing the pressure, the solid solubility of Cu, Mg and La in grains increases, the segregation along the grain boundary is reduced, the S-phase and 0-phase at the grain boundary are decreased, the brittle phase containing La increases, and the distribution of alloy elements is homogeneous. When the pressure reaches 120 MPa, the tensile strength is improved while the elongation is decreased. When the pressure is 80 MPa, the tensile strength and elongation of the alloy can reach 217.23 MPa and 10.61%, respectively.