稀土Ce对7A52铝合金组织与性能的影响

Effect of RE Ce on microstructure and properties of 7A52 aluminum alloy

采用金相、扫描电镜(SEM)观察、力学拉伸实验、剥落腐蚀实验、电化学腐蚀实验以及慢应变速率拉伸实验等分析测试方法研究稀土Ce对7A52铝合金组织与性能的影响。研究表明:稀土Ce降低合金的强度,随着Ce含量从0增加至0.6%(质量分数),合金的抗拉强度由494.81 MPa降低至476.46 MPa,屈服强度由454.24 MPa降低至435.84 MPa,伸长率由10.15%降低至7.06%;稀土Ce导致合金的耐腐蚀性能得到大幅提高,耐腐蚀性能由大到小的顺序为:0.5%Ce、0.6%Ce、0.25%Ce、0Ce。其原因是,添加稀土Ce的合金中会形成一种大块多边形状的脆性稀土相(Al_xMg_yZn_z(TiCr)_mCe),该脆性稀土相容易成为拉伸断裂的裂纹源,降低7A52铝合金的强度。同时,稀土Ce能提高合金表层氧化膜腐蚀时的电荷转移电阻(R_t),使其耐腐蚀性能得到提高。

The effects of RE Ce on the microstructure and properties of 7A52 aluminum alloy were studied by optical microstructure, scanning electron microscopy（SEM）, mechanical tensile testing, exfoliation corrosion testing, electrochemical corrosion testing and slow strain rate tensile testing. The results show that the tensile strength decreases from 494.81 MPa to 476.46 MPa, the yield strength decreases from 454.24 MPa to 435.84 MPa and the elongation decreases from 10.15% to 7.06% when Ce content increases from 0 to 0.6%（mass fraction）. The corrosion resistance of 7A52 alloy is greatly improved by Ce addition, with descending order as follows： 0.5%, 0.6%, 0.25%, 0. It is attributed to that by Ce addition, a brittle polygonal shape RE-rich-phase（AlxMgyZnz（TiCr）mCe） forms in the alloy, which becomes the crack source in the tensile test, leading to the decrease of the strength of 7A52 alloy. Moreover, the charge transfer resistance of the oxide film on the surface is enhanced by Ce addition, and thus the corrosion resistance is improved.