Microscopic and X-Ray Analysis of the Surface Changes in Aluminum Alloys during Friction
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copic and X-Ray Analysis of the Surface Changes in Aluminum Alloys during Friction O. O. Shcherbakovaa, *, T. I. Muravyevaa, **, I. V. Shkaleia, I. Yu. Tsukanova, and D. L. Zagorskiya, b a
Ishlinsky Institute for Problems in Mechanics, Russian Academy of Sciences, Moscow, 119526 Russia b Gubkin Russian State University of Oil and Gas, Moscow, 119991 Russia *e-mail: [email protected] **e-mail: [email protected] Received December 14, 2019; revised January 15, 2020; accepted January 18, 2020
Abstract—The effect of the introduction of additives of low-melting alloying elements in antifriction aluminum alloys on a change in the surface after tribological tests is estimated. Compositions are described and sample preparation is performed. For the study, a combination of electron microscopy methods (with elemental analysis) and probe microscopy (with the modes of spreading current and thermal-conductivity analysis) are used. It is shown that after heat treatment, the phase components acquire a globular shape in both alloys. Grain deformation, soft phase release to the surface, and mass transfer take place during the friction process. The hard phase components of the shoe material act as an abrasive, while mass transfer forms a film of secondary structures of variable thickness on the roller (under certain conditions, the film becomes thicker, which can lead to scuffing). The analysis of sections allows the presence of a near-surface layer (50–100 μm thick) with a modified structure to be established. The SPM method is used to establish that the thermal conductivity map at the micro level correlates with the electrical conductivity map. X-ray structural analysis of the surfaces carried out before and after tribological tests showed that the lattice spacing decreased, lattice deformation increased, and texture appeared. Keywords: aluminum antifriction alloys, tribological tests, mass transfer, film of secondary structures, electron microscopy, probe microscopy, X-ray diffraction analysis DOI: 10.1134/S1027451020040333
INTRODUCTION Over the last few years, the substitution of expensive bronzes for aluminum alloys has been a significant trend in mechanical engineering. This substitution is expedient in a number of applications, in particular, in the development of bearing assemblies [1, 2]. Here maintaining and improving high performance properties is an urgent problem [3–5]. This problem can be solved, in particular, by scientifically based selection of the alloy (base metal and alloying elements). Alloys based on aluminum meet the fundamental requirements and display antifriction characteristics comparable to bronzes. In [6–8], it was shown that alloys of the Al–5%Si–4%Cu–6%Sn system are considered optimal antifriction materials for bearing assemblies. It is also known that a change in the amount of component elements and/or adding other metals (for example, low-melting metals) can influence the structure and properties of the system alloys. Studies of the operating characteristics are carried out to estimate the effic
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