Papers by Author: Tetsuji Hoshika

Abstract: Superplastic forming characteristics of AZ31 Mg alloy recycled by solid-state process were investigated. Cylindrical scraps and machined chips were recycled by hot extrusion and hot rolling in air. As a result of tensile test, elongation to failure of the specimens recycled from small and large cylindrical scraps was almost the same as that of the rolled specimen from a virgin ingot. On the other hand, the specimen from machined chips had much lower elongation at elevated temperatures. The oxygen concentration of the specimen recycled from machined chips showed about 60 times higher value compared with that of the other specimens. In superplastic forming tests, the specimen from small and large 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.

Abstract: Blow forming characteristics of 5083 Al alloy and AZ31 Mg alloy recycled by solid state recycling were investigated. Scraps with different volume were recycled by hot extrusion and hot rolling in air. Oxide layers, which were contaminants from scrap surface, were distributed parallel to the extrusion direction in the recycled specimens. In the blow-forming test, the specimen from smaller scraps exhibited lower formability. The oxygen concentration in the recycled specimens was approximately proportional to the total surface area of scraps in the recycled specimen per unit volume. The low formability of the recycled specimens is likely to be attributed to contamination level of oxide.