Metal open-cell foams with periodic topology fabricated by spark plasma sintering

Abstract

A novel manufacturing approach to controlling the pore structure of metal open-cell foams has been conceptually demonstrated based on a periodic arrangement of high temperature porogens (a.k.a. space-holders). A process integrating structured porogen replication and spark plasma sintering (SPS) was developed to fabricate metal open-cell foams exhibiting increased control over the pore size, shape, and position. A sacrificial porogen template constructed of commercially available copper spheres arranged in a hexagonal close-packed pattern was co-sintered with nickel-titanium (NiTi) powder using SPS and subsequently leached using nitric acid. The repeatability of the foam fabrication process was investigated by characterizing the density, pore structure, and mechanical properties of the resultant open-cell foams. Spatially, the foams displayed uniform, well-replicated pore structures with a high degree of interconnectivity. During compression testing the open-cell foams exhibited unexpected brittle behavior with a high variability in ultimate strength, believed to be caused by the initiation and inter-particulate propagation of cracks through the matrix leading to sudden specimen failure.