Abstract
We synthesized the Nb-Al alloy powder from Nb and Al elemental powders by Mechanical Alloying which provides the nanometer size crystals. Mixing ratio of Nb and Al was 7.5mass%Al corresponding to the Nb3Al composition. After 720 sec milling, the grain size of milled powder was about 3nm. Spark Plasma Sintering system was applied to sinter this MA powder. At the same time, the powder obtained by Plasma Melt Gas Atomize method (Nb-26.1at%Al) was sintered by SPS for comparison. Those SPSed compacts were investigated by SEM observation, EDX analysis, X-ray diffraction and Vickers hardness measurement at high temperature.
The results obtained were as follows;
(1) The MA powder, consisting of super saturated solid solution of Nb and Al, melted partially during SPS at 1773 K, however, the PMGA powder, consisting of mixed structure of Nb and Nb3Al, didn't melted at the same temperature.
(2) The compact of MA powder by SPS had a mixed structure of Nb and Nb2Al, which was too fine to determine by SEM. On the other hand, the mixed structure consisting of Nb2Al grains and Nb3Al grains was formed in compact of PMGA powder.
(3) Vickers hardness of SPSed compact of MA powder was higher than that of PMGA powder at R.T.-1 073K.
