Early crystallization stages in a Zr-Cu-Ni-Al-Ti metallic glass

The early crystallization stages of Zr52.5Cu17.9Ni14.6Al10Ti5 metallic glass with different impurity oxygen levels were investigated with differential scanning calorimetry (DSC), high resolution electron microscopy (HREM), three-dimensional atom probe (3DAP) and small angle X-ray scattering (SAXS). While the low oxygen sample showed two peaks, the high oxygen sample showed one peak in isothermal DSC slightly above the glass transition temperatures. No evidence for the previously reported phase separation was detected in the supercooled liquid by 3DAP; compositional contrasts in SAXS and 3DAP were detected only when nanocrystals were confirmed by HREM. The low oxygen sample forms fine Ti-enriched nanocrystals and then crystallizes into Ti-poor NiZr2-phase, the high oxygen sample crystallizes into very fine NiTi2-type big cube phase.