中文摘要：

研究了熔体温度对原位自生Al-18Mg2Si（质量分数,%）复合材料组织和力学性能的影响。结果表明：随着熔体温度的提高,Al-18Mg2Si复合材料中,初生Mg2Si由粗大的树枝状变成多边形状、块状,有的成为颗粒状。熔体温度为870℃时,初生Mg2Si最细小,平均晶粒尺寸为12μm（形状因子最大）;超过870℃后,晶粒尺寸略有增大（形状因子减小）。随着熔体温度的提高,共晶Mg2Si由片层状变为颗粒状,而后又变成颗粒状和棒状的混合组织,共晶团尺寸先减小后增大。复合材料的抗拉强度、延伸率、硬度随熔体温度的提高先增大后减小,并在870℃过热时,力学性能达到最佳值。DTA分析表明,随着熔体温度的提高,合金的凝固开始温度先降低后升高,形核过冷度呈先增大后减小的变化趋势。熔体温度达到870℃时,形核过冷度最大,复合材料的硬度最大,耐磨性最好。

英文摘要：

The effects of the melt temperature on the microstructures and properties of in-situ Al-18Mg2Si composites were investigated. The results show that the coarse dendrite primary Mg2Si phases transform into the polygons and lumps and some transform into small particles with the rising of the melt temperature. The primary Mg2Si is the smallest with the average grain size of 12 μm and its shape factor is the maximum when the melt temperature is 870℃. The grain size of the primary Mg2Si increases slightly when the temperature is over 870 ℃, and its shape factor decreases. The lamellar eutectic Mg2Si transforms into small particles, and then changes into the mixed microstructure of small and rodlike particles as the melt temperature increases. The size of the eutectic group decreases first and then increases. The tensile strength, the elongation and the hardness increase first and then decrease with the rising of the melt temperature. The mechanical properties achieve the best values when the temperature is 870 ℃. The DTA analysis shows that the solidification onset temperature of the alloy decreases first and then increases, while the nucleation condenser depression first increases and then decreases, as the melt temperature is raised. The nucleation condenser depression is the largest at 870 ℃; in the meantime, the hardness of the composites achieves its maximum value and the wear-resisting property is the best.