变温搅拌制备AlSi7Mg合金半固态浆料的研究

Study on Preparation of AlSi7Mg Semi-solid Slurry by Variable Temperature Mixing Method

采用变温机械搅拌方法制备Al Si7Mg合金半固态浆料,研究了冷却速度、剪切速率对浆料组织的影响,探讨了强制对流条件下半固态浆料中球状初生相的制备机理。结果表明在强制对流机械搅拌、剪切速率40 s-1,冷却速度0.12~0.25℃/s以及剪切速率20~80 s-1、冷却速度0.12℃/s条件下制备出近球状组织的Al Si7Mg合金半固态浆料。增加剪切速率对浆料组织形貌影响不大,冷却速度是决定半固态浆料组织形貌的关键因素。强制对流下的合金熔体,在保证合金熔体温度场、溶质场均匀性和合适的冷却速度条件下,初生相就会以球状晶的特定生长方式生长,从而获得满足流变成形的半固态浆料组织。

AlSi7Mg A1 alloy semi-solid slurry was prepared by variable temperature -mechanical stirring method. The effects of cooling rate and shear rate on the microstructure of semi-solid slurry were investigated. The preparation mechanism of the semi-solid slurry was discussed. The results show that near-spheric microstructure can be obtained under forced convection, with cooling rate of 0.12-0.25 ℃/s and shear rate of 40 s1 or cooling rate 0.12℃/s and shear rate of 20-80 s1. The influence on the microstructure of semi-solid slurry is little with the increase of shear rate. The certain cooling rate is the key factor to determine the microstructure of the semi-solid slurry. The primary phase can grow to spheroidal crystal morphology in ensuring the alloy melt temperature field, solute field uniformity and the appropriate cooling rate, and the semi-solid slurry with near-spheric microstructure for rheoforming can be obtained.