Titanium compacts with controllable porosity by slip casting of binary powder mixtures

摘要

Titanium compacts with tailored porosity and pore size were fabricated by slip casting of binary powder mixtures, followed by debinding and vacuum sintering. Two different particles sizes (avg. 14 μm & avg. 56 μm) of pure titanium hydride-dehydride powder were used in six volume ratios (0:100,20:80,40:60,60:40,80:20 & 100:0). The packing density and sintering behaviour of the titanium compacts were characterised, in terms of porosity, pore size analysis, tensile properties and gas permeability. A theoretical model predicted that the green density reaches a maximum when the volume fraction of fine particles is 0.35. It was found that although experimental results showed similar behaviour there was no well-defined maximum green density. The sintered compacts showed that an increase in the volume fraction of fine powder particles reduced the porosity, permeability level and pore size, and increased the tensile properties. The relationship between permeability and porosity level was non-linear and this was caused by the differences in pore diameters in the compacts. The capillary tube model was used to discuss the relationship between the permeability, pore diameter and porosity. Using this information, a graded porosity compact was designed and fabricated by slip casting.