THE RECYCLING AND RECLAMATION OF METAL-MATRIX COMPOSITES

The development of viable techniques for the recycling and reclamation of metal-matrix composites (MMCs) is critical to the commercializatio n of these advanced materials. The recycling of both MMC wrought alloy (6061) scrap and foundry alloy (high-silicon) returns has been studie d. The MMC extrusion alloy scrap has been recycled back into direct-ch ill cast logs and the resulting billet has been tested to determine wh ether the composite properties are degraded by repeated recycling. Sim ilarly, fluxing and degassing techniques have been developed so that M MC foundry alloy gates and risers produced in shape-casting may be rec ycled back into useful castings. These fluxing and degassing processes have been tested commercially. Ultimately, when either type of MMC sc rap can no longer be recycled, the alumina particles in the wrought al loys or the silicon carbide particles in the foundry alloys may be rem oved by common salt or other fluxing techniques. Rotary salt furnace t echnology has been shown to be effective for this approach, and the re sults of large-scale trials are reported here.