熔体分散混合法制备半固态浆料

Preparation of semi-solid slurry by melt spreading and mixing technique

提出一种采用强制均匀凝固技术制备半固态浆料的新方法——熔体分散混合法。该方法通过制浆室内旋转的熔体分散器，将大体积金属液体均匀分散到低温的制浆室筒壁上，形成向下流动的厚度极小的液膜，利用筒壁对其进行冷却，实现熔体的强制均匀凝固。以Al-Si（6．56％Si，质量分数）合金为模型合金，进行浆料制备实验。结果表明：在强制熔体分散条件下，整个熔体中发生异质形核，这些晶核在均匀的温度场中以球状方式生长；经过熔体分散混合法处理，可以将温度为680-630℃、流量为0．2kg／s的熔体均匀过冷到液相线下2～15℃；制备的半固态浆料具有均匀、细小、非枝晶状微观组织，其初生相α（Al）的形状因子1．5左右，等效直径在33～70μm。

A new semi-solid slurry-making method, melt spreading and mixing technique, was proposed. In MSMT process, the melt is spreaded by rotating plat onto the wall of barrel and then distributed into thin film of melt. During flowing down along the barrel was, the melt film is cooled uniformly by the cool barrel wall. Al-Si （6.56%Si） alloy, as model alloy, was used to conduct a series of experiments. The results show that under intensive forced spreading, heterogeneous nucleation occurred continuously throughout the entire volume of the solidifying melt, and the nuclei grow spherically due to the uniform temperature created by the melt spreading and mixing. After processing by the MSMT, the melts at a temperature range between 680 ℃ and 630 ℃ and a flux 0.2 kg/s, are cooled a few degrees （2-15 ℃） below the liquidus temperature. Semi-solid slurry with non-dendritic microstructures is got steadily, the shape factors of α（Al） primary phase are about 1.5 and the sizes are about 33-70 μm.