Changes in the Defective Structure of the Surface of a Fe 77 Ni 1 Si 9 B 13 Metal Glass Ribbon under the Influence of Hy
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Changes in the Defective Structure of the Surface of a Fe77Ni1Si9B13 Metal Glass Ribbon under the Influence of Hydrostatic Pressure and Isothermal Annealing P. N. Butenkoa, *, V. I. Betekhtina, V. E. Korsukova, A. G. Kadomtseva, and M. V. Narykovaa a Ioffe
Institute, St. Petersburg, Russia *e-mail: [email protected]
Received July 13, 2020; revised July 13, 2020; accepted July 16, 2020
Abstract—The features and generality of the effect of hydrostatic pressure and annealing on the surface relief of the contact and non-contact side of the Fe77Ni1Si9B13 metal glass ribbon are revealed. The relationship between transformation of the ribbon surface inhomogeneities under these effects and possible formation of nanocrystalline regions are analyzed. We found that the evolution of the surface inhomogeneities at the contact side of the ribbon after annealing procedure leads to appearing of discrete-sized fractions in these regions. Keywords: metallic glass, surface relief, annealing, pressure, excess free volume, crystallization DOI: 10.1134/S1063783420110104
1. INTRODUCTION The great interest to amorphous metallic materials is caused by the complex of their specific physicochemical, mechanical, and magnetic properties [1–6]. Based on this, the application of so-called metallic glasses (MGs) is widening in various fields of modern technologies from space and military industry to biotechnologies and medicine. However, MGs have disadvantages such as structural instability manifested especially under temperature and mechanical influences. This imposes significant restrictions on the MG application and, at the same time, requires studying on structure and properties of such materials in initial and changed states, especially in surface layers. To some extent, the surface structure is the reflection of the processes taking place in the bulk of materials. Moreover, it is more defective and changeable than bulk [3, 7]. Heterogeneity of void and non-void nature are usually the elements of bulk defect structure and, partly, materials surface. It is known that free volume (FV) is one of the key objects in the investigation of amorphous materials. The free volume concept was proposed by Turnbull and Cohen [8] more than half a century ago, and it was developed in numerous works [10–12, 15]. To date, this concept is confirmed experimentally [13, 14]. There are two types of free volume. Excess free volume (EFV) affects changing the physicomechanical properties of the material. The removal of EFV at temperature and mechanical impact can “start” the process of nanocrystal forma-
tion [9, 15].1 It was shown experimentally that in the surface layers (1–3 μm) of Co60Fe10Si15B10, Fe56Co24Si15B15, Fe78Ni2Si8B12, and Fe85B15 metallic glasses, the main part of EFV is located as relatively large micropores (a size ~100 nm) having a slightly elongated shape, while in the bulk a more homogeneously located fine fraction (about 20–50 nm) of inhomogeneities was observed [16]. The study of the geometry of such objects, their orientation a
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