Thermal stability and crystallization kinetics of Cu-reinforced Cu47Ti33Zr11Ni8Si1 metallic glass composite powders synthesized by ball milling:: the effect of particulate reinforcement

The thermal stability and crystallization kinetics of Cu47Ti33Zr11Ni8Si1 gas atomized powder (GAP) and composite powder reinforced with 25 vol.% nanosized Cu second phase particles introduced by ball milling was studied by differential scanning calorimetry in the mode of continuous heating and isothermal annealing. Ball milling leads to successful incorporation of Cu particles within the GAP matrix and hence offers itself as a useful technique to prepare composite microstructures. In the case of continuous heating, both the glass transition temperature T-g and the crystallization temperature T-x display a strong dependence on the heating rate. The activation energy, as determined by the Kissinger equation, for the first order transformation was found to be almost identical for the GAP (3.53 +/- 0.12 eV) and composite powders (3.59 +/- 0.06 eV). The isothermal transformation kinetics were modeled by the Johnson-Mehl-Avrami (JMA) equation. The values of the JMA exponent imply that the crystallization of the metallic glass GAP as well as the composite powder is governed by diffusion-controlled three-dimensional growth. The activation energy of crystallization derived from isothermal annealing experiments is nearly the same for the GAP (3.69 +/- 0.20 eV) and the composite powders (3.78 +/- 0. 10 eV). The addition of Cut particles does not noticeably affect the crystallization kinetics of the amorphous matrix composites. (c) 2005 Elsevier Ltd. All rights reserved.