Baykov Institute of Metallurgy and Materials Science of the Russian Academy of Sciences, Moscow, Russia:

E. V. Dedyaeva, Junior Researcher, e-mail: elena.dediaeva@mail.ru
A. G. Padalko, Head of Laboratory No. 30, e-mail: padalko@inbox.ru
G. V. Talanova, Research Fellow

20 (atm) % Si – Al mini-ingots were subjected to barothermal processing (hot isostatic pressing) at the isobaric-isothermal temperature of 560 ^oC and the pressure of 100 MPa for 3 hours. It was established that after barothermal processing the initial microporosity of the aluminium alloy matrix is removed following the mechanism of plastic deformation and diffusion mass transfer resulting in a completely solid material. Using the results of metallography, scanning electron microscopy and X-ray diffraction analysis, the authors demonstrate that during a barothermal cycle the 20 (atm) % Si – Al alloy sees a bimodal distribution based on the silicon phase component with the average size of microcrystals being 5.4 μm and the size of ultradispersed silicon particles not exceeding 1 μm. The authors found that barothermal processing led to an almost 12 % reduction in the thermal expansion and a considerable reduction in microhardness compared with the initial alloy. A provision was formulated stating that the solid phase barothermal processing of the 20 (atm) % Si – Al alloy serves an effective tool for eliminating microporosity, reaching a high homogenization degree and forming a near-optimal microstructure. This would be comparable and superior to the results of regular heat treatment conducted at atmospheric and low pressure.
This research was carried out under the Governmental Assignment No. 007-00129-18-00.

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