Vacuum degassing behavior of Zr-, Ni- and Cu-based metallic glass powders

The vacuum degassing behavior of Zr55Al10Ni5Cu30, Ni59Zr15Ti13Si3Sn2Nb7Al1, and Cu54Ni6Zr22Ti18 (numbers indicate at.%) metallic glass powders has been investigated and compared with that of Al alloy powder. It was found that the alloy composition influenced the gas desorption behavior with heating in vacuo. Zr55Al10Ni5Cu30 and Ni59Zr15Ti13Si3Sn2Nb7Al1 metallic glass powders exhibited little H2 gas desorption from powder surfaces during vacuum degassing. Because Zr in the Zr-based and Ni-based amorphous alloy powders produced a native zirconium oxide layer, the surface of the Zr55Al10Ni5Cu30 and Ni59Zr15Ti13Si3Sn2Nb7Al1 amorphous alloys had no influence on adsorbed H2O. Cu54Ni6Zr22Ti18 metallic glass powder was the most affected by atmospheric H2O among the metallic glass powders examined in this study. The adsorbed H2O and Cu metal may react with each other with the formation of Cu2O and liberation of H2 during vacuum degassing. In order to obtain sound P/M final products with Cu-based P/M alloys, oxygen-free copper powders should be used in well-controlled atmospheres with low H2O partial pressures.