Structure Formation during Preparation of Variable Porosity Titanium Foams by Solid State Replication

Fabrication of variable porosity titanium foams through incorporation of sacrificial sodium chloride powder has been investigated. A three-dimensional solid foam pore skeleton containing macro- (200-400 mu m), micro- (5-10 mu m) and sub-micropores (<1.5 mu m) was formed during high temperature sintering of commercial purity titanium powder containing sacrificial sodium chloride particles, faceting of the interior pore powder surface being noted throughout. The largest macro-pores had a cubical topography representative of the sodium chloride powder that had been vaporized during heating to the sintering temperature. Formation of the smaller micro-pores appeared to have occurred during the compaction process these being retained in the specimen body due to incomplete sintering of the host powder. Finally formation of the smallest sub-micropores was associated with high temperature gas evolution and entrapment during sodium chloride vaporization.