Formation, Thermal Stability and Mechanical Properties of Ni_(60)Zr_(20)Nb_(15)Al_(5-x)Pd_x (x = 0 - 5 at percent ) Bulk Metallic Glasses

摘要

The alloying effect of Pd on the thermal stability and glass-forming ability (GFA) of Ni_(60)Zr_(20)Nb_(15)Al_5 bulk metallic glass has been investigated in the present work. The Pd substitution for Al was found to be effective in improving the thermal stability of the base alloy. The glass transition temperature (T_g) increased from 852 to 873 K with increasing Pd content. The supercooled liquid span (DELTA T_x) showed a maximum value of 55 K at the 2-3 at percent Pd compositions. The glass-forming ability of the alloy exhibited little change when the Pd content is lower than 3 at percent . Glassy rods with a critical diameter of 4 mm can be made at these minor Pd alloyed compositions. The further substitution of Pd for Al reduced GFA, and the critical BMG size was lowered down to about 2mm for Ni_(60)Zr_(20)Nb_(15)Pd_5. The room-temperature mechanical testing revealed that these newly-developed Ni-based BMGs posses a good combination of high strength and a certain amount of plasticity.