Ti-48Al-6Nb porous alloys were synthesized by the powder metallurgy (PM) method, and the associated phase transformation and pore parameter were investigated in order to reveal the pore-formation mechanism. The present results indicate that the Nb-Al and Ti-Al phase transformations contribute to the pore-formation. It was found that the five-step phase transformations for the Ti-48Al-6Nb porous alloys occur as follows: (1) Ti+Al→TiAl3 at 600-700°C; (2) Nb+Al→NbAl3 at 700-900°C; (3) TiAl3+Ti→TiAl at 900-1100°C; (4) TiAl+Ti→Ti3Al/TiAl at 1100-1350°C; (5) NbAl3+Nb→Nb2Al and the Ti3Al turns to the major phase at 1350°C. These phase transformations made the pore-diameter increasing continuously from 1.71μm to 12.10μm and also made the pore volume distributing widely. At the second step of 700-900°C, the Nb-Al phase transformation leads to 5% more volume expansion compared to the Ti-Al based porous alloys. Meanwhile, the porosity and total pore area initially increase and then decrease at this step, but they increase intensely at the final step, which is needed as a catalytic carrier.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Mechanics of Materials
- Mechanical Engineering