Cold consolidation of ATR-niobium powder under high pressure

This paper presents the results of a study concerning the consolidation of aluminothermic niobium powder under high-pressure conditions at room temperature. The method of cold powder consolidation consists of two steps: initial die-compaction followed by high-pressure treatment in almost hydrostatic conditions. The densification behaviour of the aluminothermic niobium powder during compaction was evaluated by using the compaction response diagram. The microstructure of highly dense parts was evaluated by SEM. The influence of the precompacting pressure and the high pressure on the final density was investigated. Successful compaction was obtained for precompacting pressure of up to 700 MPa and high pressure of up to 4 GPa. The niobium powder compaction is governed, at the applied high-pressure range, by mechanisms such as axial and radial plastic deformation. In addition, the experimental results showed that porosity lower than 2% can be attained under high-pressure compaction conditions, without external heat supply.