PREPARATION OF NB-CR ALLOY POWDER BY HYDROGENATION

The pulverization by hydrogenation is a new method for fabricating int ermetallic powders with high quality and low cost. In this study, the pulverization by hydrogenation was studied for various Nb-Cr alloys. T he hydrogenation was performed under the hydrogen atmosphere of 0.1 MP a in an are-melting chamber without exposure to air after are-melting. Constituent phases and lattice constants before and after hydrogenati on were examined by X-ray diffraction analysis. It is found that the p ulverization by hydrogenation occurs only in two phase alloys consisti ng of Nb solid solution (Nb-ss) and NbCr2. In the Nb-ss/NbCr2 alloys, the lattice constant of Nb-ss increases remarkably through hydrogenati on, while that of NbCr2 does not change. It is concluded that the pulv erization of the Nb-ss/NbCr2 two phase alloy is caused by large strain accompanied with lattice expansion of Nb-ss through hydrogenation and crack nucleation at intrinsically brittle NbCr2.