Pore structure and gas permeability of high Nb-containing TiAl porous alloys by elemental powder metallurgy for microfiltration application

High Nb-containing TiAl porous and gradient porous alloys were synthesized by elemental powder metallurgy (EPM). The effects of powder size on pore structure and gas permeability were investigated. It is found that pores are interconnected and skeletons consist of typical γ-TiAl/α2-Ti3Al fully lamellar microstructure for Ti–48Al–6Nb porous alloys. With the fining of particle size of Ti, Al and Nb powders, the pore size and porosity of Ti–48Al–6Nb porous alloys decrease. Otherwise, the gas permeability increases almost linearly when the porosity increases from 17% to 52% and the pore size increases from 3.18 μm to 26.69 μm. A good agreement is shown between the simulations by capillary permeability model and the results of the actual gas permeability. In addition, gradient porous alloys were fabricated using different powder sizes by constrained sintering process, and a prediction of the relationship between permeability and coating thickness was discussed. Results from this study indicate the potential applications in microfiltration development by tailoring porosity of the coating.