A new process for efficient purification of 6061 aluminum alloy scrap under semi-solid and super-gravity conditions

Abstract

A new method for efficient and sustainable recovery of pure Al from 6061 aluminum alloy scrap based on semi-solid processing and supergravity separation was proposed in this study. Firstly, the microstructural variations of the alloy scraps after semi-solid isothermal treatment (SSIT) were investigated, and the liquid phase accumulated with a large amount of impurity elements would gradually aggregate at the grain boundaries and eventually form a dendritic network, while the spherical Al particles within the grain had high purity. Subsequently, the inter-dendritic liquid was successfully extruded from the intergranular by super-gravity separation technology and the pure Al was efficiently recovered. In this process, the effects of separation time (i.e., isothermal treatment time, t), separation temperature (i.e., isothermal treatment temperature, T) and gravity coefficient (G) on the purification effect were evaluated. The recovery rate of pure aluminum (Al ≈ 99.3 wt%) was 81.98% at the optimum conditions of t = 15 min, T = 640 °C, G = 500. In addition, it was found that increasing the separation time and temperature was beneficial to the purification effect of the alloy scrap but had a negative impact on the recovery rate. Therefore, this study has designed a new process for super-gravity purification and recovery, which realized cyclic recycling and significantly improves the recovery efficiency of aluminum scrap.