UCLA

Invar metal matrix composites, incorporating amorphous silica ranging from 0-50vol%, were produced with the intention of processing the composites using additive manufacturing. These composites were aimed to have a lower density and CTE than that of pure Invar. Densities ranging from 7.44 g/cm3 (92% of theoretical) to 4.79 g/cm3 (93% of theoretical) were attained for pure Invar and the 50/50 composite respectively when sintered at 1250oC for 5 hours. These high temperatures were necessary to sinter the silica-rich regions of the composite however at temperatures exceeding 1200oC, the phase separation of iron silicate was observed on the surface of 90/10 vol% samples. X-ray diffraction also found the amorphous silica would devitrify to cristobalite and tridymite during sintering. These crystalline forms of silica have a larger CTE than Invar, which resulted in a CTE increase with the addition of silica in the composites.