Crystallization characteristics of the Ti53Cu47 amorphous allay

A thin Ti53Cu47 amorphous ribbon was prepared by rapid quenching from the m elt. The crystallization behavior was investigated by differential scanning calorimetry (DSC), X-ray diffraction (XRD), and transmission electron micr oscopy (TEM). The DSC results indicated that the activation energy for crys tallization was 170 or 150 kJ/mole (1.76 or 1.55 eV/atom) based on the Kiss inger or Arrhenius plot, respectively, which is close to that of chemical d iffusion in the TiCu alloy: 166 kJ/mol (1.72 eV/atom). The Johnson-Mehl-Avr ami (JMA) plot exhibited a linearity, with an exponent of n = 2.0 +/- 0.2. The XRD patterns revealed the transformation to the equilibrium gamma -TiCu phase. However, broad peaks due to nanocrystalline grains were not observe d. From the TEM analysis, there was a metastable phase with an fee structur e based on the Cu structure pre-existing in the as-quenched ribbon. Only a few TiCu particles in the nanoscale dimension were observed to precipitate from the amorphous matrix upon both continuous and isothermal heatings. A t heoretical calculation demonstrates that amorphous Ti53Cu47 has a very low nucleation frequencey and thus, a low tendency to form nanocrystals.