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采用金相显微镜、扫描电镜和X射线衍射仪等手段,研究了质量分数为0%~0.5%的镧对Al-Zn-Mg-Cu合金铸态组织的影响。结果表明:La元素能有效抑制Al-Zn-Mg-Cu合金的晶粒长大,起到细化晶粒的作用;合金中La超过一定含量后,细化效果减弱,不均匀化程度增加。当La含量为0.3%时,铸态组织中基体晶粒细化效果最显著,晶粒减小到50μm左右;铝合金的第二相粒子主要包括η(MgZn_2)相、θ(Al_2Cu)相、S(Al_2CuMg)相和富La的AlZnMgCu相,并且弥散分布在晶界上。
The effects of lanthanum (0% ~ 0.5%) on the as-cast microstructure of Al-Zn-Mg-Cu alloy were investigated by metallographic microscope, scanning electron microscopy and X-ray diffraction. The results show that La can effectively inhibit the grain growth of Al-Zn-Mg-Cu alloy and refine the grains. When La exceeds a certain content, the refining effect is weakened and the degree of heterogeneity is increased. When the content of La is 0.3%, the grain refinement effect is the most significant in the as-cast microstructure, and the grain size is reduced to about 50 μm. The second phase particles of the aluminum alloy mainly consist of η (MgZn 2) phase, θ (Al 2 Cu) phase, S (Al 2 CuMg) phase and La-rich AlZnMgCu phase, and dispersedly distributed on the grain boundary.