Viscous Flow Behaviour of Supercooled Liquids and Mechanical Properties in Zr-Cu-Ni-AI Bulk Metallic Glasses

摘要

Viscous flow behaviour of supercooled liquids and mechanical properties in Zr_(55+X)Cu_(30-X)Ni_5Al_(10) (X=0, 5 and 10 at. %) and Zr_(65)Cu_(18)Ni_7Al_(10)bulk metallic glasses (BMGs) have been examined. Viscosity has been measured by using a penetration viscometer at a high-speed heating rate of 400 K/min. With increasing Zr-content, T_g tended to decrease and T_x tended to increase, resulting ΔT_x (=T_x-T_g) increaseing up to about 170 K under a heating rate of 400 K/min by the DSC analysis. The viscosity lowered about one order of magnitude, e.g., minimum value of the viscosity decreased from 3～4×10~6 Pa-s for the Zr_(55)Cu_(30)Ni_5Al_(10) and Zr_(60)Cu_(25)Ni_5Al_(10) BMGs down to 5～6×l0~5 Pa-s for the Zr_(65)Cu_(20)Ni_Al_(10) and Zr_(65)Cu_(18)Ni_7Al_(10) BMGs under the same heating condition. Compression tests were also carried out at a slow strain rate of about 1 × 10~(-4) s~(-1) at room temperature. With increasing Zr-content, the apparent yield stress was decreased but the total strain at fracture was increased significantly, suggesting that there is a strong relationship between viscosity and the mechanical properties in these BMGs.