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球磨时间对纳米晶Al-7Si-0.3Mg合金粉末微观组织及硬度的影响

Effect of milling time on microstructures and hardness of nanocrystalline Al-7Si-0.3Mg alloy powders

  • 摘要: 以机械破碎Al-7Si-0.3Mg合金粉末为原料进行高能球磨, 对不同球磨时间的合金粉末进行金相观察、X射线衍射分析、透射电镜表征及显微硬度测试, 研究球磨时间对纳米晶Al-7Si-0.3Mg合金粉末的影响。结果发现, 高能球磨导致共晶硅颗粒从微米尺度细化到亚微米尺度, 颗粒形状从多面体转变成圆形, 颗粒内部有层错生成。随着球磨时间逐渐增加到60 h, 合金粉末平均颗粒尺寸从134μm逐渐下降到22μm, Al(Si, Mg)基体晶粒尺寸从438 nm降低到23 nm, 粉末显微硬度从HV 93增加到HV 289。粉末硬度的增加主要归功于球磨导致的晶粒细化(细晶强化作用), 此外, 球磨过程中硅颗粒的细化以及球磨引起的Mg、Si原子在基体内固溶度的增加也有利于粉末硬度的提高。

     

    Abstract: Al–7Si–0.3 Mg alloy powders produced by mechanical crushing were subjected by high energy ball milling in different times, the optical microscopy(OM), X-ray diffraction analysis(XRD), transmission electron microscopy(TEM), and microhardness test were used to investigate the effect of milling time on the microstructures and hardness of Al–7 Si–0.3 Mg alloy powders. The results show that, the sizes of eutectic Si particles significantly reduce from the micrometer level to the submicrometer level by high energy ball milling, the particle shape changes from the polyhedron to the circular, and the stacking faults appear in the Si particles. With increasing the milling time to 60 h, the average particle size of the alloy powders is reduced from 134 μm to 22 μm, the grain size of the Al(Si, Mg) matrix is reduced from 438 nm to 23 nm, and the microhardness of the powders is increased from HV 93 to HV 289. The increase of hardness is mainly attributed to the grain refinement caused by ball milling, which results in a strong fine grain strengthening effect. The refinement of silicon particles during ball milling and the increase in solid solubility of Mg and Si atoms in the matrix caused by ball milling are also contributed to the hardness increase.

     

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