Fabrication of MMCs from metal and alloy powders produced from scrap

Metal matrix composites (MMCs) present a lot of advantages over conventional engineering materials due to their improved properties. In the present work, Ni3Fe–Al2O3 and (3Ni + Fe)–Al2O3 composites with a 100–65 wt% metals or alloy content were prepared. For that purpose, lower cost Ni, Fe and Ni3Fe powders, recovered from ferrous scrap by a hydrometallurgical process recently developed, with properties similar to typical commercial grades, were used along with commercial Al2O3 powder. An established simple and economical fabrication technique was applied, comprising uniaxial cold pressing and sintering. The composite microstructures were characterized by optical, scanning electron microscopy, EDX and XRD analysis. Density measurements were also performed by the Arcimedes’ method. The used metallic powders generally showed a satisfactory behavior in the fabrication steps leading to the successful development of particle reinforced MMCs containing no phases other than the constituent and exhibiting a sintering degree varying with the ceramic content. Important porosity levels were revealed, that were more pronounced in the Ni3Fe-based composites, in which zinc stearate was demanded as a lubricant.