Annealing Effects on Viscosity of Zr_(55)Cu_(30)Al_(10)Ni_5 Supercooled Liquids

摘要

Viscous flow behavior in supercooled liquid region of as-cast and annealed Zr_(55)Cu_(30)Al_(10)Ni_5 bulk metallic glasses has been examined by using a penetration viscometer under various heating rates of 20, 200 and 400 deg C/min. Applied load for the cylindrical-shaped penetration indenter with a diameter of 1 mm was varied from 0.049 N to 0.294 N. Viscosity was quite independent of these applied loads under the various heating conditions. When the sample was slowly heated at the rate of 20 deg C/min, viscosity exhibited relatively high values that may be mainly due to the skin effects of oxides on the sample surface. At the heating rate of 200 deg C/min and above, viscosity (eta) largely decreased and tended to saturate. By annealing the bulk metallic glasses at 400 deg C, the density of the glasses increased, while the crystallization temperature (T_x), the viscosity and the activation energy for viscous flow in their soopercooled liquid decreased gradually with increasing the annealing time. The specific behaviour of viscosity has been explained by the formation of particles during annealing for relaxation.