Enthalpy relaxation and its relation to the thermodynamics and crystallization of the Zr58.5Cu15.6Ni12.8Al10.3Nb2.8 bulk metallic glass-forming alloy

This paper reports on the thermodynamics, on the enthalpy relaxation kinetics, and on the crystallization kinetics of the Zi(58.5)Cu(15.6)Ni(12.8)Al(10.3)Nb(2.8) bulk metallic glass-forming alloy. The thermodynamics functions were determined from heat of fusion and specific heat capacity measurements. A novel differential scanning calorimetric method was optimized for the measurement of the enthalpy relaxation in the vicinity of the glass transition. The residual enthalpy frozen-in the glass is found to relax with stretching exponents approaching unity, which indicates rather strong glass behavior, reflected also by the high value of the fragility parameter and the small driving force for crystallization. The apparent activation energy for both, enthalpy relaxation and primary crystallization is the same as for the diffusion of the midsize atoms suggesting that their mobility controls both processes, but on different time and length scale. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.