(1. 常州大学 材料科学与工程学院，常州 213164；
2. 常州大学 先进金属材料常州市重点实验室，常州 213164；
3. 三一重工股份有限公司，长沙 410100)
摘 要: 将Al-21%Si(质量分数)合金在750~1 200 ℃分别重熔保温20、40、60、80、100和120 min后铜模快冷及重熔保温120 min后空冷，采用光学显微镜观察分析合金中初晶硅形态与尺寸的变化，对Al-21%Si合金中的初晶硅的溶解动力学进行分析。结果表明：过热温度越高，初晶硅尺寸越细小。在铜模快凝条件下，在750和850 ℃重熔时，保温时间对初晶硅颗粒尺寸的影响较大；在950~1 200 ℃重熔时，保温时间对初晶硅颗粒尺寸基本没有影响。当合金空冷时，即使过热温度足够高也不能获得细小的初晶硅组织，较高的过热温度和较快的冷却速度有利于消除过共晶铝硅合金中粗大初晶硅的遗传现象和获得细小的初晶硅。短时重熔实验和溶解动力学分析表明，当合金在1 200 ℃重熔并保温7~10 min后就可以使Al-21%Si合金中的初晶硅基本溶解。当重熔温度为950 ℃时，需要保温1.4~1.7 h才能使初晶硅得到溶解。
关键字: 初晶硅；组织遗传；溶解动力学；过热温度；快速凝固
（1. School of Materials Science and Engineering, Changzhou University, Changzhou 213164, China;
2. Key Laboratory of Advanced Metal Materials of Changzhou City, Changzhou University, Changzhou 213164, China;
3. Sany Heavy Industry Co., Ltd., Changsha 410100, China）
Abstract:The Al-21%Si alloy was rapidly cooled in copper mould after being overheated at 750−1 200 ℃ for 20, 40, 60, 80, 100 and 120 min, respectively. It was also dry quenched after being overheated at 750−1 200 ℃ for 120 min. The changes of the morphology and particle size of primary Si were analyzed with optical microscopy. The solution kinetic of primary Si in Al-21%Si melt was analyzed. The results show that the particle size of primary Si gradually decreases with the increase of overheating temperature. The effect of holding time on the particle size of primary Si is obvious as remelted at 750 and 850 ℃, and that is little as remelted at 950−1 200 ℃, when the alloy is cooled in copper mould. Fine primary Si microstructure cannot be obtained when the alloy is dry quenched even if the overheating temperature is quite high. High overheating temperature and rapid solidification are beneficial to eliminate the heredity of coarse primary Si in hypereutectic Al-Si alloy and to obtain the fine primary Si. Short-time remelt experiments and solution kinetic analysis indicate that the primary Si in Al-21%Si alloy can be mostly dissolved after the alloy is remelted at 1 200 ℃ for 7−10 min. When the remelt temperature is 950 ℃, the holding time of 1.4−1.7 h is needed for the solution of primary Si.
Key words: primary Si; structural heredity; solution kinetic; overheating temperature; rapid solidification
