Solid-state recycle processing for magnesium alloy waste via direct hot forging

A solid-state recycle processing for magnesium alloy waste has been developed by combining cyclic plastic working and direct hot forging under the short thermal explosion. AZ91D machined chips, which were employed as wasted materials in this study, were consolidated to the green compact with fine microstructures via bulk mechanical alloying (BMA) process, where the compaction and forward extrusion in the closed die were repeated at room temperature. To keep fine microstructures after hot forging, that is, to prevent from the matrix softening due to the grain and/or intermetallic growth, the thermal damage on the green compact in pre-heating before forging was controlled by using the infrared gold image rapid heating furnace. The hot forged AZ91D alloy showed superior mechanical properties such as hardness and ultimate tensile strength (UTS) to the cast one used as input raw materials. The same effects were recognized in the case of wasted Al-Si alloys via this process. The developed solid-state recycle processing revealed a possibility to improve the mechanical properties of the consolidated light alloys even in employing their wasted materials.