稀土Y对Al-8%Mn合金微观组织和性能的影响

采用光学显微镜、扫描电子显微镜、电子探针和X射线衍射仪,研究了Al-8%Mn合金熔体中添加稀土Y质量分数对合金微观组织的作用机制,并分析了稀土Y添加量对合金力学性能和耐蚀性能的影响规律.结果表明:稀土Y能有效细化Al-8%Mn合金中的Al₆Mn化合物相和α-Al相.当Y的添加质量分数为3%时,细化效果最佳,使Al₆Mn相的形貌由粗大板条状和块状转变为细小块状,平均尺寸由未细化前的67.4 μm减小到36.5 μm,α-Al由粗大的柱状晶细化成等轴晶,其平均尺寸减小至48 μm.稀土Y添加后Al-8%Mn合金的抗拉强度和延伸率分别由组织未细化前的126 MPa和1.47%增加到141 MPa和2.26%,分别提高了12.0%和76.9%.此外,在30 g NaCl+10 mL HCl+1 L H₂O溶液中的腐蚀研究表明,随着Al-8%Mn合金中稀土Y添加量的增加,合金的抗蚀性能逐渐变差.

Effect of rare earth yttrium addition on the microstructure and properties of Al-8%Mn alloy

The optical microscope, SEM, electron probe and XRD were used respectively in this research to investigate the dominant mechanism of rare earth Y added in Al-8%Mn alloy melt on microstructure of the alloy. The effect of amount of rare earth Y on the mechanical properties and corrosion resistance of the alloy was analyzed as well. Our results show clearly that the addition of rare earth Y can refine Al₆Mn compounds and α-Al phases in Al-8%Mn alloy during alloy solidification. Moreover, after adding 3wt.% Y to Al-8%Mn alloy melt, the refining efficiency caused by Al₆Mn and α-Al phases is most significant. The morphology of Al₆Mn phases changes from coarse lath to small piece and blocky, and the average size of Al₆Mn reduces from 67.4 μm to 36.5 μm. Hence, the morphology of α-Al phase transfers from coarse columnar crystal to equiaxed crystal, and the average size decreases to 48 μm when 3wt.%Y is added to Al-8%Mn alloy melt. Both the ultimate tensile strength and elongation of Al-8Mn-3wt.%Y alloy are improved up to 141.37 MPa and 2.26% respectively. In the end, the addition of rare earth reduces the intergranular corrosion resistance of the alloy in etching solution (30 g NaCl+10 mL HCl+1 L H₂O).