稀土La和Ce对7A04铝合金组织与性能的影响

Effect of rare earth La and Ce on microstructure and properties of 7A04 aluminum alloy

采用扫描电镜、能谱仪、万能试验机和电化学工作站等研究了单一稀土(La或Ce)以及混合稀土(La和Ce)的添加对7A04铝合金微观组织与性能的影响。结果表明:在7A04铝合金中添加稀土La和Ce后,沿晶界有块状和棒状的稀土相析出,并使呈连续网状分布的第二相变成断续分布,合金的二次枝晶组织得到细化,其中添加单一稀土Ce对合金的细化效果最好,平均晶粒尺寸为20μm;添加单一稀土La或Ce以及不同比例的混合稀土La和Ce后,7A04铝合金的力学性能和耐腐蚀性能均有所提高,性能由大到小依次为:添加单一稀土Ce、混合稀土La∶Ce=5∶5、单一稀土La、混合稀土La∶Ce=3∶7、混合稀土La∶Ce=7∶3、无稀土,说明单一稀土Ce的添加对7A04铝合金性能改善效果最好,其显微硬度、抗拉强度、伸长率分别为125.4 HV0.5、532.5 MPa和10.8%,相比未添加稀土元素的铝合金,分别提高了72.7%、30.9%和74.2%。

Effect of single rare earth(La or Ce)and mixed rare earth(La and Ce)addition on microstructure and properties of 7A04 aluminum alloy was studied by means of scanning electron microscopy,energy dispersive spectrometer analysis,universal testing machine and electrochemical workstation.The results show that after the addition of rare earth La and Ce in the 7A04 aluminum alloy,there are massive and rod-like rare earth phases precipitated along the grain boundary,the second phase with continuous network distribution becomes discontinuous distribution,the secondary dendrite structure of the alloy is refined,and the addition of single rare earth Ce has the best refining effect on the alloy,with an average grain size of 20μm.After adding single rare earth La or Ce and mixed rare earth La and Ce with different proportions,the mechanical properties and corrosion resistance of the 7A04 aluminum alloy have been improved.The properties of the alloy from large to small are as follows:adding single rare earth Ce,adding mixed rare earth La∶Ce=5∶5,adding single rare earth La,adding mixed rare earth La∶Ce=3∶7,adding mixed rare earth La∶Ce=7∶3,and no rare earth adding,indicating that the addition of single rare earth Ce has the best effect on improving the properties of the 7A04 aluminum alloy,and its microhardness,tensile strength and elongation is 125.4 HV0.5,532.5 MPa and 10.8%respectively,which is 72.7%,30.9% and 74.2% higher than that of the aluminum alloy without rare earth elements.