Formation and compression mechanical properties of Ni–Zr–Nb–Pd bulk metallic glasses

The formation of bulk metallic glasses (BMGs) and their room temperature mechanical properties have been investigated in a serial of Ni65−xZr20Nb15Pdx (x = 0∼15; at.%) quaternary alloys, which are hopefully hydrogen-permeation materials. The partial substitution of Ni with Pd in Ni65Zr20Nb15 alloy has proved to be effective in improving glass-forming ability (GFA) and thermal stability. In particular, good BMG-forming compositions were revealed within the Pd content range of 2.5–12.5 at.%, and BMG rods of 3 mm in diameter were successfully made at compositions Ni57.5Zr20Nb15Pd7.5 and Ni55Zr20Nb15Pd10 by copper mold casting. The addition of Pd enhanced the thermal stability of the supercooled liquid. With an increase of Pd content, the supercooled liquid span, ΔTx = Tx − Tg, increased from 29 K at Ni65Zr20Nb15 to 47 K at Ni52.5Zr20Nb15Pd12.5. The Pd-bearing BMGs exhibited high fracture strength, which ranged from 2750 to 2850 MPa. These Pd-bearing BMGs showed a certain degree of toughness, and the highest plastic strain, about 2%, was reached in the Ni60Zr20Nb15Pd5 BMG.