Separation Technology of Tramp Elements in Aluminium Alloy Scrap by Semisolid Processing

A growing number of studies suggest that the accumulation of unwanted elements is a growing problem in all recycled material streams. Thus, the separation of tramp elements from aluminium alloy scrap is very important in the aluminium recycling process. In this paper, a new technique of backward extrusion in the semisolid state is reported for separating the tramp elements from aluminium alloy scrap and obtaining high-purity aluminium easily and quickly. In this process, partial solidification is adopted to condense tramp elements in the liquid phase on the grain boundary. In experimental trials, four aluminium alloys were selected: cast aluminium alloy (AC4C), two kinds of wrought aluminium alloy (A7N01, A7075) and aluminium beverage can scraps. From the results of macro-and optical microscopic analysis, Rockwell hardness testing and electron probe micro-analyser (EPMA) analysis, it was confirmed that the backward extrusion in the semisolid state could separate the tramp elements from the aluminium alloy scrap easily and high-purity aluminium was obtained.