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

The vacuum degassing behavior of Zr 55Al 10Ni 5Cu 30, Ni 59Zr 15Ti 13Si 3Sn 2Nb 7Al 1, and Cu 54Ni 6Zr 22Ti 18 (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. Zr 55Al 10Ni 5Cu 30 and Ni 59Zr 15Ti 13Si 3Sn 2Nb 7Al 1 metallic glass powders exhibited little H 2 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 Zr 55Al 10Ni 5Cu 30 and Ni 59Zr 15Ti 13Si 3Sn 2Nb 7Al 1 amorphous alloys had no influence on adsorbed H 2O. Cu 54Ni 6Zr 22Ti 18 metallic glass powder was the most affected by atmospheric H 2O among the metallic glass powders examined in this study. The adsorbed H 2O and Cu metal may react with each other with the formation of Cu 2O and liberation of H 2 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 H 2O partial pressures.