稀土Y对Mg-15Al合金组织及摩擦磨损行为的影响

通过合金制备、微观分析和摩擦磨损测试等手段,研究了不同含量的稀土元素Y对Mg-15Al合金相微观组织和摩擦磨损性能的影响。实验结果表明,加入钇后,Mg-15Al合金的α-Mg晶粒明显细化,α+β共晶组织由粗大的网状变得分散、细小,钇与铝形成稳定的Al2Y化合物,钇的加入量为0.8%时,组织细化效果最好,此时晶粒尺寸最小为23.05μm。当钇加入量超过0.8%时,α-Mg晶粒又变大,力学性能下降。稀土镁合金的摩擦磨损特性明显优于基体合金,稀土元素的加入增强了磨损表面氧化膜的稳定性,提高了稀土镁合金的承载能力,有效延迟了由轻微磨损向严重磨损的转变过程。

Microstructure and mechanical properties of cast Mg-15Al-xNd alloy by permanent mold

To improve the comprehensive mechanical properties of Mg-15AI magnesium alloy, different amounts （from 0 to 4.0wt.%） of Nd were added to the alloy and six Mg-15AI-xNd alloys were prepared by metal mould casting. The effect of Nd content on microstructure of the alloys was investigated by means of OM, SEM, EDS, TEM, and XRD. The tensile properties were tested at room temperature （RT） and high temperature （473 K）. The results indicate that the primary a-Mg dendrite is significantly refined with the addition of Nd. The best refinement is reached at 1.0wt.% Nd content and the average dendrite arm spacing decreases from 80- 100 pm （without Nd addition） to -20 pm. A further increase in Nd content leads to the coarsening of the primary a-Mg dendrite. The addition of Nd improves the tensile properties of Mg-15AI both at RT and 473 K. The Mg-15AI alloy containing 1.0wt.% Nd exhibits the best tensile properties. Compared with the alloy without Nd, the yield and ultimate tensile strength of the Mg-15AI-1.0Nd alloy at RT increase from 132.3 to 148.6 MPa and 152.3 to 189.6 MPa, increase by 12.3% and 24.5%, respectively; and the elongation at RT increases from 0.05 % to 1.24%. The yield and tensile strength of the alloy at 473 K increase from 97.9 to 115.3 MPa and 121.6 to 140.1 MPa, increase by 15.2% and 20%, respectively. Further increment of Nd content to 1.5wt.% degrades the tensile properties, which is ascribed to grain coarsening and growth of the AI-Nd phase.

不同合金元素对Mg15Al镁合金显微组织与腐蚀性能的影响

研究了Zn、Si、Nd三种元素对Mg15Al镁合金微观组织和腐蚀性能的影响,通过金相显微镜和XRD分析了Mg15Al-X合金的显微组织。结果表明:三种元素都能使Mg15Al合金的晶粒细化,Nd的细化效果最好。Mg15Al-1Zn中不出现新相,但是Zn的加入可促进β相的形成,而Mg15Al-1Si和Mg15Al-1.5Nd中分别出现了汉字状或块状新相Mg2Si和针状新相Al11Nd3,促使β相成均匀连续网状结构。添加Si元素,增加了β相含量,Mg2Si相与β相形成屏障保护α-Mg基体;添加Nd元素,β相含量减少,抑制了α-Mg基体与β相之间的微电偶腐蚀,从而提高了Mg15Al合金的耐腐蚀性。