Influence of Cu on Crystallization Kinetics of Zr-Co-Al Metallic Glass

Effect of Cu alloying on the crystallization kinetics of Zr-Co-Al metallic glass (MG) is investigated under non-isothermal conditions using differential scanning calorimetry (DSC). Activation energies for Zr72Co24Al4 (ZCA) and Zr72Co16Cu8Al4 (ZCCA) MGs are determined by employing Kissinger's technique. Further, variation of activation energy during crystallization process is investigated for both ZCA and ZCCA MGs. The influence of nucleation and growth mechanism on the crystallization process is understood using local Avrami exponent from the data obtained under non-isothermal conditions. Crystallization pathway in terms of phase formation during devitrification of ZCA and ZCCA MGs is investigated for samples annealed at 973 K and the phases identification is carried out using X-ray diffraction analysis. Addition of Cu lowers the activation energy and influences the phase formation in Zr-Co-Al MGs. Cu destabilizes the transformation of ZrCo and alpha Zr in ZCCA and results in precipitation of Zr3Co and Zr0.98Cu0.02 phases.