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Crystallization Behavior of Mechanically Alloyed Zr-Cu-Al-Ni Glass Composites Containing Second-Phase ZrC Particles
Published online by Cambridge University Press: 11 February 2011
Abstract
We report on mechanical alloying of elemental powders with nominal composition Zr55Cu30Al10Ni5 together with up to 30 vol.% of ZrC particles which results in the formation of a metallic glass matrix in which the carbide particles are homogeneously dispersed and, at the same time, reduced to nanometer size. The thermal stability is investigated by isochronal differential scanning calorimetry and is found to be strongly affected by increasing the ZrC volume fraction. Comparison with calorimetric data for single-phase mechanically alloyed Zr-Cu-Al-Ni-C glassy powders suggests that dissolved carbon, originating from non-negligible ZrC-dissolution processes during mechanical alloying, is responsible for the changes in the glass transition and the crystallization behavior. Isothermal calorimetric data are also presented and discussed in the framework of the Johnson-Mehl-Avrami model. The carbon atoms dissolved in the glassy phase are suggested to slow down the kinetics of overall crystallization. On the other hand, for large ZrC volume fractions nucleation of crystalline phases is promoted by the second-phase particles and changes in the Avrami exponent from n = 4 to n = 3 suggest that the nucleation rate approaches zero after the early stages of crystallization.
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- Copyright © Materials Research Society 2003