Blow forming of Mg alloy recycled by solid-state recycling

Blow forming characteristics of AZ31 Mg alloy recycled by solid-state recycling were investigated. Cylindrical scraps and machined chips were recycled by hot extrusion and hot rolling in air. Oxide layers were observed in the recycled specimens by oxygen mapping with EPMA (Electron Probe Micro Analyser). The interval of the oxygen layers for the specimen from machined chips was much shorter than that for the specimen from cylindrical scraps. As a result of tensile tests, the mechanical properties of the specimen from cylindrical scraps were found to be almost the same as those of a rolled specimen from a virgin ingot. On the other hand, at elevated temperatures, the elongation of the specimens from machined chips was low, compared with those of the rolled specimens from a virgin ingot. The large amount of oxide contamination is likely to be responsible for the lower elongation of the specimens from machined chips. In blow-forming tests, the specimen from cylindrical scraps exhibited excellent formability similar to the rolled specimen from a virgin ingot. However, the specimen from machined chips showed poor formability. Thus, oxide contamination adversely affected the formability of recycled Mg alloy.