Sustainable recycling of aluminum scraps to recycled aerospace-grade 7075 aluminum alloy sheets

Abstract

The production of aerospace-grade aluminum alloy sheet is characterized by stringent demands, resulting in a low yield rate. The processing of this material generates considerable amounts of highly alloyed scrap, complicating its recycling due to the challenge of maintaining melt cleanliness. This study employed an aerospace-grade melt refining system to purify the recycled 7075 alloy melt obtained from comprehensive scrap remelting. The melt's cleanliness was assessed using Porous Disc Filtration Analysis (PoDFA) and Liquid Metal Cleanliness Analyzer (LiMCA) and Alscan. The microstructure of the ingots and sheets was examined through Scanning Electron Microscopy (SEM) and Electron Backscatter Diffraction (EBSD), whereas the mechanical properties of recycled sheets were evaluated and benchmarked against those of primary sheet at an aerospace-certified testing facility. The findings indicate that the recycled 7075 sheet meets aviation standards, with no significant differences in microstructure or performance when compared to primary sheet. Furthermore, the study highlights the economic benefits of recycling scrap, revealing a potential cost saving of $4210.8 per ton of recycled sheet. The findings presented herein offer a theoretical framework and empirical evidence supporting the development of a recycling system for aerospace scraps and the certification of airworthiness for recycled aerospace aluminum alloy.