The effect of boron on the thermal properties of the zirconium-based bulk amorphous alloys

Abstract

Abstract Ribbons of amorphous Zr 65− x Al 7.5 Cu 17.5 Ni 10 B x alloys with 0.1 mm thickness were prepared by melt-spinning. The thermal properties and microstructural development during the annealing of amorphous alloys have been investigated by the combination of differential thermal analysis (DTA), differential scanning calorimetry (DSC), high-temperature optical microscope, X-ray diffractometry (XRD), and transmission electron microscopy (TEM). The glass transition temperature for the Zr 65− x Al 7.5 Cu 17.5 Ni 10 B x alloys were measured around 645 K. The crystallization temperature increased with increasing boron content to 4 at.% and obtained a relative large temperature interval Δ T x of around 88 K. The calculated T rg for Zr 65 Al 7.5 Cu 17.5 Ni 10 alloy, Zr 63 Al 7.5 Cu 17.5 Ni 10 B 2 alloy, and Zr 61 Al 7.5 Cu 17.5 Ni 10 B 4 alloy exhibit the same value of 0.57. The activation energy of crystallization for the Zr 61 Al 7.5 Cu 17.5 Ni 10 B 2 alloy was about 360 or 380 kJ/mol, as determined by the Kissinger or Avrami plot, respectively. These values are about 20% higher than the activation energy of crystallization for the base alloy (314 kJ/mol as determined by the Kissinger plot). The average value of the Avrami exponent n were calculated to be 1.96±0.25 for Zr 65 Al 7.5 Cu 17.5 Ni 10 alloy, 1.75±0.15 for Zr 63 Al 7.5 Cu 17.5 Ni 10 B 2 alloy, and 1.9±90.45 for Zr 61 Al 7.5 Cu 17.5 Ni 10 B 4 alloy. This indicates that these three alloys exhibit similar crystallization process, a diffusion controlled growth process with a decreasing nucleation rate.