Solid state recycling of Mg-Gd-Y-Zn-Zr alloy chips by spark plasma sintering

The consolidation Mg-Gd-Y-Zn-Zr billets containing long period-stacking ordered (LPSO) phase were recycled from the metal chips through the spark plasma sintering (SPS) process, which achieves the effective metallurgical bonding between metal chips. The effects of the sintering parameters on the microstructure characteristic and mechanical properties of the recycled billets were studied. The metal chips were effectively bonded in the recycled billets sintered at 500 degrees C, however, the metal chips partly melted into semi-solid state as sintering temperature increased to 550 degrees C. The oxidation films of rare earth (RE) element formed at the bond interface between metal chips during SPS recycling process. The consolidation recycled billets through SPS demonstrated the rival compression failure strain and superior compression stress compared with the referenced cast alloy. The lamellar 14H-LPSO phases hardly precipitate in the vicinity of the bond interface between metal chips after heat treatment with air cooling. However, the furnace cooling facilitates the precipitation of 14H-LPSO phases within the alpha-Mg grains, even the alpha-Mg matrix adjacent to the bond interface. The oxide films at the bond interface between the metal chips were zigzagged and fragmented during the isothermal compression. The cracks or holes were hardly observed adjacent to the bond interface during isothermal compression, which reveals superior bond properties and deformation consistency performance between metal chips. (C) 2020 Published by Elsevier B.V. on behalf of Chongqing University.