快速凝固过共晶铝硅合金的微观组织特征及耐磨性研究

利用单辊旋淬快速凝固法制备Al-21Si和Al-30Si过共晶铝硅合金,采用扫描电镜、透射电镜及XRD技术对所制备合金的组织形貌和相结构进行表征.结果表明:快速凝固合金形成微纳米晶组织,晶粒明显细化.Al-21Si过共晶合金凝固组织由羽毛针状(α-Al+β-Si)共晶体和雪花状α-Al相组成;快速凝固有效抑制初生硅相的形核与生长,α-Al相领先共晶形核生长,形成微纳米级亚共晶组织.Al-30Si高硅过共晶合金初生硅相细小钝化,初晶Si相显微结构为孪晶形貌,呈典型的过共晶组织特征.快速凝固显著提高了合金的显微度和耐磨性,快速凝固Al-21Si合金的耐磨性是传统铸造合金的5倍.

Microstructure and Wear Resistance of Rapidly Solidified Hypereutectic Al-Si Alloys

Rapidly solidified hypereutectic Al-21 Si and Al-30Si alloys were prepared by a single roller melt-spinning technique. The microstructure and phases of the alloys were characterized using scanning electron microscopy (SEM) , transmission electron microscopy (TEM) and X-ray diffraction (XRD). Fine grains with a micro-nano composite microstructure were obtained by rapid solidification. The microstructures of the Al-21 Si alloys were characterized by primary micro-nanostructured a-Al phase and feather-needle-like α-Al + β-Si eutectic. The nucleation and growth of primary silicon were effectively inhibited, α-Al phase had a higher priority to nuclate and grow than eutectic α + Si phase. The hypereutectic Al-21 Si alloy showed the hypoeutectic microstructure. The primary Si phases in Al-30Si alloy were fine twins. And this microstructures were a typical hypereutectic microstructure. Microhardness and wear resistance (i. e. 5 times as high as that of traditional casting alloys) of alloys were greatly improved by rapidly solidification.