Nivala, Peter Thompson, authorJames, Susan P., advisorPuttlitz, Christian M., committee memberPopat, Ketul, committee memberHeyliger, Paul R., committee member2019-01-072019-01-072018https://hdl.handle.net/10217/193191Metal open-cell foams are competitively poised to meet the demands of next generation applications due to the ability to tailor their properties to achieve multifunctionality through material selection and control of the pore structure. The topological design of metal foams must consider many factors including pore size, shape, spatial distribution, and interconnectivity; however, the current manufacturing techniques limit the degree to which the tailored pore structures can be realized. In the current research, a novel manufacturing approach to tailoring the pore structure of metal open-cell foams has been conceptually demonstrated based on a structured assembly of porogens. A process integrating space-holder replication and spark plasma sintering (SPS) was developed to fabricate metal open-cell foams exhibiting increased control over the pore size, shape, and position. The pore structure consisted of spherical copper porogens arranged into a hexagonal close-packed pattern. This sacrificial template was co-sintered with nickel-titanium (NiTi) powder using SPS and subsequently leached using nitric acid. The resultant NiTi open-cell foams were characterized for their spatial and mechanical properties, which exhibit uniform, well-replicated pore structures with a high-degree of interconnectivity. During compression testing the open-cell foams displayed unexpected brittle behavior, which was traced to the initiation and inter-particulate propagation of cracks through the NiTi matrix leading to sudden specimen failure. Additionally, the Master Sintering Curve (MSC) concept was utilized to investigate the effect of copper porogens on the densification behavior of NiTi during the fabrication of open-cell foams. Typically, the MSC is used to determine the apparent activation energy (QMSC) for sintering densification of powder materials and to predict the final specimen density under arbitrary time-temperature sintering profiles. The MSC predicted the areal matrix density of the NiTi open-cell foams to within 1.2%. Comparisons of the densification behavior between NiTi and NiTi with copper specimens suggests the porogens have little to no effect on the densification behavior of NiTi powders within the current experimental setup. The manufacturing approach demonstrated within the current research will be extended to leverage advanced manufacturing techniques, such as additive manufacturing, to realize optimum pore structures for multifunctional applications to enable the next generation of open-cell foams exhibiting higher performance at lower cost and less weight.born digitaldoctoral dissertationsengCopyright and other restrictions may apply. User is responsible for compliance with all applicable laws. For information about copyright law, please see https://libguides.colostate.edu/copyright.metal open-cell foamporogenspark plasma sinteringperiodic topologymaster sintering curvespace holder replicationText