Sr+RE在Al-40wt%Si合金中的复合变质作用

Compound Modification Effect of Sr+RE on Al-40 wt%Si Alloy

研究了Sr+RE复合变质对Al-40wt%Si合金的组织和性能的影响。结果表明,Sr+RE复合变质处理不仅对初晶硅和共晶硅具有变质作用,对枝晶α也有明显的细化作用。当RE加入量保持不变,随着Sr加入量的增加,初晶硅由角块状或大板片状先变为小块状再变为多角的大块状,边、角钝化;共晶硅由针片状变为纤维状加短杆状,最后为密实短杆状,甚至粒状;枝晶α由高度发达的树枝状转变为等轴晶,分布均匀。另外,随Sr加入量的增加,合金力学性能得到显著提高,抗拉强度提高37%,伸长率增加1倍多,硬度提高21%;当Sr加入量为0.05wt%～0.077wt%时,组织形貌最理想,综合力学性能最优。

The effects of Sr ＋ RE complex modification on microstructure and mechanical properties of Al-40 wt% Si alloy were investigated. The results show that Sr ＋ RE complex modification not only has modifying effect on primary silicon and eutectic silicon, but also has significant refining effect on dendrite α. When the RE addition remains constant, with the increas of Sr addition, the primary silicon firstly changes from polygonal block or large plate to small block, then to large polygonal block, its edge and corner is passivated; the eutectic silicon changes from needle to fibrous sheet plus short rod, then to dense short rod, or even the granular, the dendrite α changes from highly developed dendritic shape to equiaxed shape and its distribution is uniform. In addition, with the increase of Sr addition, the alloy＇s mechanical properties significantly improves, its tensile strength is increased by 37%, its elongation is more than double, its hardness is increased by 21%; when the Sr addition is between 0.05 wt% and 0.077 wt%, the microstructure and mechanical properties are best.