熔体温度对Al-18%Mg2Si复合材料组织与性能的影响

Influences of Melt Temperature on Microstructures and Properties of in-situ Al-18%Mg2Si composites

摘要:

本文主要研究了熔体温度对原位自生Al-18%Mg₂Si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-18%Mg₂Si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7μm,超过870℃后,晶粒尺寸略有增大；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结果及分析表明,熔体温度为870℃时,原位自生Al-18%Mg₂Si复合材料组织和性能最佳,是形核过冷度大和生长方式改变的综合作用结果。

Abstract:

The effects of the melt temperature on the microstructures and properties of in-situ Al-18%Mg₂Si composites were investigated. The results show that the coarse dendrite primary Mg₂Si phases transformed to the polygons and lumps and some transformed to small particles with the rising of the melt temperature. The primary Mg₂Si is the smallest with the average grain size of 7μm when the melt temperature is 870℃.The grain size of the primary Mg₂Si increased slightly when the temperature is over 870℃.The lamellar eutectic Mg₂Si transformed to small particles, then changed into the mixed microstructure with small and rodlike particles with increasing the melt temperature. The size of the eutectic group decreased first and then increased. The tensile strength, the elongation rate and the hardness increased first and then decreased with the rising of the melt temperature. The mechanical properties achieved the best value when the temperature is 870℃.The result and analysis of DTA show that the microstructure and mechanical properties of in-situ Al-18%Mg₂Si composites are the best, which results from the comprehensive function of multiple factors including large nucleation undercooling and the change of growth pattern.