Prominent ?-relaxation and stress relaxation decoupling phenomenon in Gd-Ni-Al metallic glasses

GdxNi20Al80-x (x = 50, 60, 65, 70 at%) metallic glasses (MGs) with prominent fl -relaxation were developed, which provide a new model system for studying some controversial issues concerning fl -relaxation. The relaxation behavior and thermal stability of GdxNi20Al80-x MGs were probed by dynamic mechanical re-laxation, static stress relaxation, and differential scanning calorimetry. In view of the temperature and frequency dependence of the dynamic mechanical relaxation spectrum, we investigated the fl-relaxation and a -relaxation separation phenomena of Gd50Ni20Al30 and Gd60Ni20Al20 MGs. With increasing Gd/Al ratio, the activation energy of the fl -relaxation decreased, which was conducive to the flow units and prominent fl-relaxation. The Gd70Ni20Al10 alloy had the most significant fl-relaxation phenomenon, although some nanocrystalline Gd3Ni phase was distributed in the amorphous matrix. The Gd50Ni20Al30 glass had a crystallization activation energy of 476 kJ/mol, corresponding to the highest thermal stability. At a constant strain, the static stress relaxation process of the Gd70Ni20Al10 alloy was analyzed over a wide time window and temperature range. A decoupling phenomenon of the relaxation into a two-step process occurred in the Gd70Ni20Al10 alloy, namely, a fast relaxation process and a slow relaxation process, at different time scales. Analysis of the relaxation dynamics and time scales of the relaxation confirmed that the fast relaxation process differed from the fl-relaxation process. This study elucidates the fl -relaxation behavior and stress relaxation decoupling phenomenon in Gd-Ni-Al MGs and should, therefore, help clarify the mechanical relaxation behavior and intrinsic characteristics of MGs in future work.(c) 2023 Elsevier B.V. All rights reserved.