工艺参数对引晶法制备半固态浆料组织的影响

Influence of process parameters on semi-solid slurry prepared by introducing grain process

采用引晶法（Introducing Grain Process,简称IGP）制备半固态金属浆料,研究了工艺参数对半固态A356铝合金浆料组织的影响,讨论了球状初生α（Al）晶粒的形成机制及形貌控制.结果表明：当合金温度为630℃、制备浆料为4 kg时,如果引晶尺寸为10 mm、加入量为3.5%（质量分数）和倾倒温度为611～617℃,半固态浆料中初生α（Al）晶粒的平均直径可达40-75μm,形状因子可达0.82-0.89.如果引晶尺寸为10 mm、倾倒温度为613℃、加入量为2%-4%,初生α（Al）晶粒的平均直径可达45-82μm,形状因子可达0.78-0.88.合金温度和倾倒温度适当降低、或者引晶加入量适当提高,组织越好.当QR=QA、Rh=Rc时,只要倾倒温度适宜就可以制备优质半固态浆料.引晶熔化时产生的枝晶碎块是半固态浆料中初生α（Al）晶粒的直接来源,引晶熔化时形成的温度过冷区也为异质形核提供了有利条件.

Semi-solid metal slurry was prepared by introducing grain process （IGP）. The influence of the process parameters on microstructures of the semi-solid A356 Al-alloy slurries were investigated, and formation mechanism and morphology controlling of the spherical primary α （Al） grains was discussed. The results show when the alloy temperature is 630 ℃, the preparing slurry is 4 kg, the IG size is 10 mm, dosage is 3.5 % （mass fraction）, and dumping temperatures（DTs） are at 611-617 ℃, the mean diameters of the primary α（Al） grains in the semi-solid slurries can reach 40-75 p,m and the shape factors can reach 0.82-0.89. When the IG size is 10 mm, the DT is at 613 ℃, and dosage is 2 %-4 %, the mean diameters can reach 45-82 μm and the shape factors can reach 0.78-0.88. With the alloy temperature and the DT decreasing or the dosage increasing properly, the primary α（Al） grain morphology is better. When QR =QA and Rh= Rc, as long as the DT is suitable, excellent semi-solid slurry can be produced. As a result of the IG melting, a large amount of dendritic fragments can become direct source of the primary α（Al） grains. Meanwhile, many under-cooled areas are formed, where abundant primary or（A1） grains are multiplied by heterogeneous nucleation.