Point Defects, Recovery Kinetics and Ordering in Irradiated Bulk Metallic Glasses
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Point Defects, Recovery Kinetics and Ordering in Irradiated Bulk Metallic Glasses Yuri Petrusenko1, Alexander Bakai1, Valeriy Borysenko1, Dmitro Barankov1, Oleksandr Astakhov1, and Michael-Peter Macht2 1 National Science Center "Kharkov Institute of Physics & Technology", Kharkov, 61108, Ukraine 2 Hahn-Meitner-Institut Berlin, Berlin, D-14109, Germany ABSTRACT The problem of structural properties and structural defects of amorphous solids is still of vital importance. To make clear whether stable point defects exist in metallic glasses (MGs) or not, we have studied the accumulation and recovery kinetics of radiation defects in ZrTiCuNiBe and ZrTiCuNiAl bulk MGs irradiated with 2.5 MeV electrons at T ~ 80 K. The electrical resistance measurements of the irradiated samples were performed. The recovery spectrum of irradiationinduced electrical resistance was measured for the 85–300 K temperature range. The most important result of the recovery experiments is that they clearly show the annealing stages for the irradiated samples. Two annealing peaks located at T~150 K and T~225 K are resolved for ZrTiCuNiBe glass. Similar peaks are also revealed for ZrTiCuNiAl. It can be concluded from the data that the defect mobility is a thermally activated process, and that the activation energy is not as high as that for vacancies in crystalline alloys. Thus, the data obtained testify in favor of the structure with “perfect” local ordering of atoms. It should be noted that this property is basic in the formulation of the polycluster model of amorphous solids. INTRODUCTION The microscopic structure of amorphous solids, and especially of metallic glasses, remains not quite understood up to now because of many difficulties met in direct observation of disordered structures at the atomic level. Several models of the metallic glass structure have been proposed. The most advanced and widely used in interpretation of the physical properties of glasses was for a long time the densely random-packed spheres (DRPS) model. The basic DRPS model was developed by Bernal [1] to simulate the structural properties of fluids. This model and a series of its modifications were also used in the physics of metallic glasses on the assumption that their structural properties are similar to those of simple liquids [2, 3]. The main features of a DRPS glass are a poor short-range order (SRO) and a comparatively low density. As a result, as shown by computer simulations [4], point defects appear to be unstable in the DRPS structures. Based on experimental observations, ideas of prevailing “perfect” SRO and medium-range order (MRO) in metallic glasses were formulated and repeatedly reincarnated in different models of the glass structure [5-10]. These ideas underlie the polycluster model [8-10], which includes a self-consistent description of the structure and structural defects of glasses. A polycluster amorphous solid consists of locally regular clusters, which are separated by intercluster boundaries. Several types of the SRO are randomly alterna
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