In Situ Investigation of Structural Evolution in Zr46Cu46Al8 and Zr56Cu36Al8 Bulk Metallic Glasses During Isothermal Annealing

The crystallization kinetics of Zr₄₆Cu₄₆Al₈ and Zr₅₆Cu₃₆Al₈ bulk metallic glasses (BMGs) during isothermal annealing in the supercooled liquid region has been studied using in situ simultaneous differential scanning calorimetry (DSC) and small-angle neutron scattering (SANS) technique. Zr₄₆Cu₄₆Al₈, known for its good glass forming ability (GFA), exhibits a complex crystallization pathway. Initially, a transition region emerges, eventually evolving into the thermodynamically stable crystalline phase of Cu₁₀Zr₇, facilitated by continuous chemical redistribution at the late stage of annealing. In contrast, Zr₅₆Cu₃₆Al₈, a poor glass former, crystallizes directly into the thermodynamically stable crystalline phase of CuZr₂ in a single step, with no observed chemical redistribution. Overall, the results suggest that continuous chemical redistribution following structural ordering may contribute to stabilizing the amorphous state and improving the thermal stability of BMGs. This study highlights the critical role of chemical redistribution in the crystallization of BMGs and introduces a new perspective for assessing their GFAs.