Separating Behavior of Nonmetallic Inclusions in Molten Aluminum Under Super-Gravity Field

A new approach to separating nonmetallic inclusions from aluminum melt by super gravity was investigated. To figure out the separating characteristics of inclusions under super-gravity field, the aluminum melt containing MgAl2O4 spinel particles was treated with different separating times at 1023 K (750 °C). The significant region with inclusion accumulated appears in the bottom area of the sample obtained by centrifugal separation, and thickness of the region decreases with the increase of the separating time; especially, at the gravity coefficient G = 20, time t = 5 minutes, all inclusions nearly migrate to the bottom of the sample. In addition, the volume fraction, number density, and average size of inclusions gradually increase in the samples along the direction of super gravity, and the distributed gradients of inclusions become sharper with the increase of the separating time. Moreover, the moving velocities of inclusions were theoretical studied for the first time. The moving velocities obtained experimentally agree well with the theoretical ones calculated by Stokes’ law at G ≤ 20, t ≤ 2 minutes. However, there are obvious differences between the experimental and theoretical moving velocities under the conditions of G ≥ 100, t = 2 minutes. It is indicated that Stokes’ law is applicable to the melt with low gravity coefficient in this system.