Influence of porosity on mechanical behaviour and gas permeability of Ti compacts prepared by slip casting

Porous titanium compacts with porosity in the range of 12.3-35.3 vol% were fabricated by slip casting. Slip casting is emerging to be an attractive process for fabrication of porous titanium products. The mechanical properties, fracture morphology, gas permeability, pore size analysis and pore shape factors for the porous Ti compacts were determined for different porosity levels. A decreasing porosity level resulted in less open porosity and gas permeability, reduced pore size, and an increased tensile stress and elongation. The mechanical properties of porous titanium compacts produced by slip casting were comparable with more conventional press and sintered materials at the same porosity levels. Theoretical models for tensile stress and ductility as a function of porosity were examined and incorporated into the results and differences between the theoretical models and experimental results are discussed. The pore shape factor analysis showed that tensile loading would stretch the pores in the compacts to produce more irregular pores, which were acting as linkage sites to allow the propagation of cracks. Additionally, a novel interconnected pore characterisation method using ammonium meta-tungstate solution is presented. By using backscatter scanning electron microscopy, the interconnected pores can be directly observed.