Environmentally benign fabricating process of magnesium alloy by cyclical plastic working in solid-state

Solid-state processing via cyclically plastic working to output the green compact has been developed to fabricate magnesium alloys with fine microstructures. The relationship between the energy consumption during the plastic working and the characteristics of hot extruded magnesium alloys was evaluated from the viewpoint of the environmentally benign process. The cyclical plastic working marks a significant advance in refining microstructures, such as matrix grain and silicon particles added to synthesize Mg₂Si via solid-state reaction with magnesium. For example, the grain size of hot extruded AZ31 alloy is 3-15 μm, which is remarkably smaller than that with 20-80μm in employing the cold compact without using such a plastic working. As a result of the grain refinement, AZ31 alloys reveal higher UTS of 330-355 MPa than the conventional alloys of 270 MPa. The energy consumption of the cyclical plastic working with 200 cycles is 10 kJg^-1 to fabricate the billet consolidated by hot extrusion, when using a high-speed screw-driven press machine. This is less than 10% of the energy consumed by the conventional recycling process in re-melting wasted magnesium alloys (126 kJg^-1). This process is highly capable of producing high performance magnesium alloys with a small energy consumption and is environment-friendly.