Chair “Physical Problems of Material Science”, National Research Nuclear University MEPhI (Moscow Engineering Physics Institute), Moscow, Russia:

G. N. Elmanov, Assistant Professor, e-mail: GNElmanov@mephi.ru
E. A. Ivanitskaya, Post-Graduate Student
V. I. Skrytnyy, Senior Researcher
E. S. Zharikov, Post-Graduate Student

Changes in the structure, phase composition and topology of the surface of metallic glasses Ni – (Cr, Fe, Si, B) were investigated on different crystallization stages at the temperature range of 450–650 ^oС by differential thermal analysis, X-ray diffraction analysis (XRD), atomic force microscopy, scanning electron microscopy and energy-dispersive X-ray microanalysis. There were investigated the Ni_71.5Cr_6.8Fe_2.7B_11.9Si_7.1 and Ni_63.4Cr_7.4Fe_4.3Мn_0.8B_15.6S_i8.5 alloys, appointed according to the American Welding Society as AWS BNi2. Metallic glasses were obtained in the form of belts with 0.04–0.05 mm thickness by speed cooling from liquid state. The sequence of formation of crystalline phases was defined together with their structure and nature of chemical elements redistribution during crystallization of these metallic glasses. The processes, which occur during crystallization, are clearly shown by the surface topology change. α-Ni-based solid solution crystals (80–100 nm diameter) are formed on initial crystallization stage at the temperature range of 450–500 ^oС in amorphous matrix. At the same time, the basic boron mass is displaced on the crystal boundaries and amorphous phase. At the second stage (500–550 ^oC), the residual amorphous phase is crystallized in fine metastable -phase with М₂₃B₆ crystal structure. At the third stage (more than 550–600 ^oC), the -phase changes the structure into Ni3B with low silicon content, and Ni₃Si crystals with low boron content are formed on the boundaries. Finally, strongly projecting Ni3B crystals with identical size are formed on the sample surface. At the temperatures, close to the melting, formation of boride crystals (Cr, Ni, Fe)B with high chromium content, which have a specific elongate pyramidal shape, was observed by scanning electron microscopy, instead of XRD-method.

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