Composition dependence of open-volume relaxation in Zr-Cu-Al bulk amorphous alloys studied by positron annihilation

• Published in: Journal of alloys and compounds Vol. 707; pp. 73 - 77
• Main Authors: Hori, F., Ishii, A., Ishiyama, T., Iwase, A., Yokoyama, Y., Konno, T.J.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 15.06.2017; Elsevier BV
• Subjects: Alloys; Aluminum base alloys; Amorphous alloys; Annealing; Bulk density; Differential scanning calorimetry; Energy distribution; Eutectic alloys; Free volume; Glass transition temperature; Isothermal annealing; Local chemical order; Metallic glasses; Positron annihilation; Structure relaxation; Studies; Temperature; X-ray diffraction; Zirconium base alloys; Free volume; Local chemical order; Positron annihilation; Structure relaxation
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2016.12.416

Structural relaxation behavior of various composition for Zr-Cu-Al ternary bulk amorphous alloys (hyper-eutectic: Zr45Cu45Al10 and Zr49Cu41Al10, eutectic: Zr50Cu40Al10, hypo-eutectic: Zr55Cu35Al10 and Zr60Cu30Al10) during isothermal annealing below glass transition temperature (Tg) has been investigated by positron annihilation techniques (positron lifetime and coincidence Doppler broadening (CDB)), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and bulk density measurements. The annealing makes the positron lifetime decrease owing to the relaxation. However, maximum decreasing of positron lifetime after 10 ks annealing for eutectic alloy was observed. And different composition dependence of positron change between hypo- and hyper-eutectic alloys was confirmed. Especially, open-volume in hyper-eutectic alloys is hard to change by the annealing. We found that the trend of positron lifetime change Δτ with Zr concentration is not necessarily correlated with the change in bulk density consistently. On the other hand, the positron lifetime during annealing obeys a stretched exponential relaxation function. Also we found the relaxation parameter β, which indicates the distribution activation energy for open-volume relaxation, varies in Zr concentration. •The nature of open-volume was classified by hyper- and hypo-eutectic alloy region.•Composition dependence of open-volume relaxation for BA alloys was confirmed.•Relaxation process of open-volume obeys stretched exponential function.•Open-volume relaxation divided into two composition regions essentially.