Investigation of Superplasticity and Formation of Embedded Zones in Beryllium

I. I. Papirov$^{1}$, A. A. Nikolayenko$^{1}$, V. S. Shokurov$^{1}$, A. V. Shokurov$^{1}$, Yu. V. Tuzov$^{2}$

$^{1}$National Science Center ‘Kharkiv Institute of Physics and Technology’, NAS of Ukraine, 1 Akademichna Str., UA-61108 Kharkiv, Ukraine
$^{2}$National Research Nuclear University ‘MEPhI’ (Moscow Engineering Physics Institute), 31 Kashirskoe Shosse, RU-115409 Moscow, Russian Federation

Received: 08.02.2018. Download: PDF

As a result of long-term research, for the first time, the authors succeeded in obtaining high-purity fine-grained beryllium, which is by the order of magnitude more plastic then technical metal at room temperature and passes to superplastic state at elevated temperatures. This review summarizes the results of the study of nature of superplastic flow and high-temperature deformation of beryllium. The coefficient of high speed sensitivity of fine-grained high-purity beryllium and alloys based on it is determined in the ranges of temperatures, 823–1023 K, and strain rates, 10$^{-5}$–10$^{-3}$ с$^{-1}$. As found, the texture of beryllium practically does not change under the superplastic flow. The superplastic deformation is characterized by a strong inhomogeneity of the local plastic flow against the background of the relative homogeneity of the macroscopic flow. As established, the superplasticity of beryllium is a complex process involving sliding along grain boundaries, various variants of grain rearrangement, dislocation and diffusion creep, as well as the formation of embedded zones in grains. The restructuring of grains is also a complex process, which is a result of the joint operation of both the Ashby–Verrall mechanism and the Gifkins’s one. As found, during a high-temperature creep of beryllium, in the body of the grain and near its boundaries, specific deformation reliefs called as embedded zones are formed. As revealed, the formation of embedded zones has a diffusion nature. A mechanism for their formation and growth is proposed; it differs from the classical Herring–Nabarro diffusion creep due to shortened mass-transfer paths.

Key words: fine-grained beryllium, superplasticity, embedded zones, grain boundary.



PACS: 61.72.Mm, 62.20.fq, 62.20.Hg, 66.30.Fq, 81.40.Ef, 81.40.Lm, 83.60.La

Citation: I. I. Papirov, A. A. Nikolayenko, V. S. Shokurov, A. V. Shokurov, and Yu. V. Tuzov, Investigation of Superplasticity and Formation of Embedded Zones in Beryllium, Metallofiz. Noveishie Tekhnol., 40, No. 6: 817—843 (2018) (in Russian)

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