Effect of pressure on beta relaxation in La60Ni15Al25 metallic glass

HY Xu and HW Sheng and MZ Li, JOURNAL OF APPLIED PHYSICS, 123, 125108 (2018).

DOI: 10.1063/1.5021383

The effect of pressure on beta relaxation in La60Ni15Al25 metallic glass (MG) was investigated by activation-relaxation technique in combination with molecular dynamics simulation. It is found that the beta relaxation behavior and the potential energy landscape are significantly modulated by pressure. With increasing pressure, the atomic motion in beta relaxation in La60Ni15Al25 MG changes from hopping-dominated to the string-like-dominated motion with increased activation energy. Moreover, while the hopping motion is gradually suppressed as pressure is increased, the cooperative rearrangements with more atoms involved but very low activation energies are significantly enhanced by pressure. It is further found that the "subbasins" in the potential energy landscape in La60Ni15Al25 MG become deeper and steeper with increasing pressure, leading to the increase of activation energy. Meanwhile, some neighboring "subbasins" merge under pressure accompanied by the disappearance of energy barriers in-between, leading to events with very low activation energies in the beta relaxation. The atomic structure analysis reveals that the transformation of atomic motions in beta relaxation in La60Ni15Al25 MG under pressure is strongly correlated with the decrease of pentagon-rich atomic clusters and the increase of clusters with fewer pentagons. These findings provide a new understanding of the beta relaxation mechanism and some clues for tuning beta relaxation in MGs. Published by AIP Publishing.

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