【摘要】 采用Al-Si-P中间合金对Al-25%Si合金熔体进行变质处理,研究了P含量和变质温度对初生硅尺寸和形态的影响规律。利用金相显微镜、扫描电子显微镜观察了硅相和AlP化合物的形态,X射线衍射仪测定了变质细化合金的衍射图谱和择优取向。利用最小二乘法计算了硅相的点阵常数。结果表明,当加热温度为880℃、保温时间为30 min时,在Al-25%Si合金熔体中加入0.07%P可以将初生硅相细化至50μm以下。其相关细化机理为,一方面Al-Si-P中间合金内生的AlP化合物在熔体中溶解后重新析出,增加了异质形核的核心,使晶粒细化。另一方面,P变质使初生硅相晶面间距和点阵常数增大,生长过程中的择优分布消失,抑制了晶粒长大,使晶粒尺寸减小。但随着P添加量增加以及变质温度的升高,熔体中的AlP化合物溶解度增大,不利于晶粒细化。更多还原

【Abstract】 Al-25%Si alloy melt was modified by Al-Si-P master alloy. The effects of P content and melt temperature on the size and shape of primary Si phase in Al-25%Si alloy were studied. The morphologies of Si phase and AlP compound were observed on OLYMPUS-DSX500 i metalloscope and LEO-1450 scanning electron microscope. Diffraction patterns and preferred orientation were measured by Siemens D5000 X-ray diffractometer. Lattice constant of Si phase was calculated with the least square method. The results show that Si phase with regular block shape in Al-25%Si alloy can be refined to below 50 μm by adding Al-Si-P master alloy with 0.07%P into melt at 880 ℃ and holding 30 min. This can be attributed to two aspects. On the one hand, endogeneous AlP compound in the Al-Si-P master alloy dissolves and re-precipitates in melt, which act as heterogeneous nucleus of the primary Si; on the other hand, the modification causes crystal plane spacing and lattice constant of primary Si phase to enlarge and preferred distribution to disappear, which restrains the Si phase growth. However, with P content increasing and melt temperature rising, the dissolubility of AlP compounds in melt will increase, which is not conducive to grain refinement.更多还原