Optimization and characterization of novel injection molding process for metal matrix syntactic foams

Abstract

Metal matrix syntactic foams are particulate composites comprised of hollow or porous particles embedded in a metal matrix. These composites are difficult to manufacture due primarily to the lightweight, relatively fragile filler material. In this work, an injection molding process was developed for metal matrix syntactic foams. First, an aqueous binder was optimized for low-pressure injection molding. A mixture model was used to optimize the composition of the binder to achieve the highest relative density. The model predicted the maximum relative density was at a binder composition (in vol.%) of 7% agar, 4% glycerin, and 89% water. Second, this binder was used to manufacture copper matrix syntactic foams with 0, 5, 10, and 15 vol.% porous silica as the filler material. The solids loading for these compositions decreased with increasing filler material from 55 to 44 vol.%, likely due to binder filling the pores in the porous silica particles. Finally, the sample quality after injection molding was characterized. Only 0.11 ± 0.06 vol.% carbon remained in the samples. Silica particles were well-dispersed in the samples after sintering, and they did not appear to be fractured. The specific strength of the copper matrix material increased with increasing porous silica additions.