LAUSR

Abstract The crystallization kinetics of Zr55Cu30Al10Ni5 and (Zr55Cu30Al10Ni5)98Nb2 melt-spun metallic glasses in non-isothermal and isothermal conditions were studied by differential scanning calorimetry. According to the non-isothermal and isothermal conditions, the crystallization activation energy for the Nb-containing sample is lower than the Nb-free sample, suggesting that crystallization transformation becomes easier by Nb microalloying. The time-temperature-transformation (TTT) diagrams demonstrate that the Nb minor addition delays the onset of crystallization by shifting the incubation time to longer times, but then accelerates the crystallization progress by shortening the endset time of crystallization, yielding a narrower crystallization transformation region. The Avrami exponents for both non-isothermal and isothermal conditions have larger values in Nb-containing sample, revealing increased nucleation rates in this glassy alloy. In the isothermal condition, the Avrami exponent values in both alloys are either above or below 2.5, indicating that the governing crystallization mechanism is diffusion-controlled three-dimensional growth with either decreasing or increasing nucleation rate.