Crystallization kinetics and thermal stability of mechanically alloyed Al76Ni8Ti8Zr4Y4 glassy powder

Al76Ni8Ti8Zr4Y4 glassy powder was produced by mechanical alloying process. The phase structure and the crystallization kinetics as well as the thermal stability were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and differential scanning calorimeter (DSC) in non-isothermal mode. The glassy alloy powder shows a distinct one-stage crystallization process with a wide supercooled liquid region. Crystallization occurs by the precipitation and growth of FCC-Al, with intermetallic compound AlTi, AlTi3, Al2Y and Al3Zr. The non-isothermal crystallization kinetics is analyzed by the modified Johnson-Mehl-Avrami (JMA) equation. The values of the Avrami exponent imply that the dominating crystallization mechanism of the present glassy powder is two- or three-dimensional nucleation and growth controlled by diffusion of atoms. The present glass powder has a large supercooled liquid region (SLR) Delta T-x value (86 K) and the apparent activation energy for crystallization is as high as 316 kJ/mol. The thermal stability was also evaluated by continuous transformation diagram (CHT) obtained by the extended Kissinger equation. To convince the thermal stability for a very long period of time, a quick annealing of the glassy powder at 700 K for 24 h was conducted and the related result was discussed. (C) 2013 Elsevier B.V. All rights reserved.