Comparative study of thermal stability and crystallization kinetics between melt-spun and bulk Pd77.5Cu6Si16.5 metallic glasses

A comparative study on the thermal stability and kinetics of crystallization of both melt-spun and bulk Pd77.5Cu6Si16.5 metallic glasses was performed. Rapidly quenched Pd77.5Cu6Si16.5 ribbon and as-cast bulk metallic glass (BMG) sample were produced by melt spinning and copper mold casting, respectively. Phase identification and transformation were studied by X-ray diffraction (XRD), transmission electronic microscopy (TEM), and differential scanning calorimeter (DSC) measurements. In non-isothermal conditions, the activation energies were calculated by Moynihan and Kissinger methods, respectively. The nucleation and growth during the crystallization were investigated in the frame work of the local activation energy and the local Avrami exponent. The local activation energy was calculated by Kissinger-Akahira-Sunose, Flynn-Wall-Ozawa and Vyazovkin methods. The local Avrami exponent was calculated. The experimental results indicated that the characteristic temperatures depend on the heating rate. The obtained activation energies indicated that the Pd77.5Cu6Si16.5 amorphous alloys exhibit excellent thermal stability. The thermal stability of Pd77.5Cu6Si16.5 BMG is better than that of ribbon. The local activation energy E-a increases to a maximum and then decreases. It is indicated by local Avrami exponent that the crystallization processes of both Pd77.5Cu6Si16.5 amorphous ribbon and BMG are controlled by volume nucleation with three-dimensional growth with various nucleation rates. The crystallization process of Pd77.5Cu6Si16.5 amorphous ribbon is close to that of BMG. The isothermal crystallization kinetics of Pd(77.5)Cu(6)Si(16)(.5 )amorphous ribbon is investigated and compared with the results of non-isothermal crystallization kinetics. (C) 2022 The Authors. Published by Elsevier B.V.

Automated summary

A comparative study was conducted on the thermal stability and kinetics of crystallization of melt-spun and bulk Pd77.5Cu6Si16.5 metallic glasses. The results showed that the Pd77.5Cu6Si16.5 amorphous alloys have excellent thermal stability, with the bulk metallic glass exhibiting better stability than the ribbon. The crystallization processes of both the ribbon and the bulk metallic glass were found to be controlled by volume nucleation with different nucleation rates, as indicated by the local Avrami exponent.