FREE-VOLUME CHANGES IN THE BULK METALLIC-GLASS ZR46.7TI8.3CU7.5NI10BE27.5 AND THE UNDERCOOLED LIQUID

Volume changes in Zr46.7Ti8.3Cu7.5Ni10Be27.5 bulk metallic glass have been observed by positron-annihilation and density measurements. Exces s volume of the order of 1% is quenched in the bulk glass at cooling r ates as low as 1-2 K/s. The isothermal relaxation kinetics obey a Kohl rausch law with beta exponents of similar to 0.3 between 180 and 230 d egrees C. The effective activation energy is similar to 0.7 eV. Struct ural relaxation is not accompanied by severe embrittlement. The outer surface is shown to play a crucial role in annealing of excess volume. Relaxed excess volume is restored completely after heat treatment in the undercooled liquid state. The observed free-volume changes contras t with the behavior of perfectly strong glasses. [S0163-1829(98)09017- 1].