Solid-state recycling for machined chips of iron by hot extrusion and annealing

Solid-state recycling for machined chips of pure iron by hot extrusion at 823 K and annealing at 1073–1273 K was carried out. The as-extruded solid recycled specimen without annealing was fractured prior to yielding at room temperature. However, high ductility was recovered by annealing at 1073–1273 K. This is because the oxides at the interface of the machined chips dispersed in grain by annealing. The annealed solid recycled specimens showed higher yield stress than the annealed virgin extruded specimens. Grain refinement for the solid recycled specimens was enhanced by the high dislocation density in the machined chips, resulting in higher strength in the recycled specimens. Thus, the solid-state recycling is a low energy upgrade recycle process.