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RISS 인기검색어
- 검색키워드
- 저자 : Zhilyaev, A.P. (검색결과 3 건)
- 무료
- 기관 내 무료
- 유료
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Rapid synthesis of an extra hard metal matrix nanocomposite at ambient temperature
Ahn, B.,Zhilyaev, A.P.,Lee, H.J.,Kawasaki, M.,Langdon, T.G. Elsevier Sequoia 2015 Materials science & engineering. properties, micro Vol.635 No.-
The strengthening of metals is essentially controlled by the microstructures of the metal solids and it is well understood that smaller grain sizes lead to higher hardness and increased strength. Nevertheless, true bulk nanostructured materials are difficult to produce using established engineering techniques, especially when considering the practical and societal needs of materials selection. Lightweight Al and Mg are conventional metals having excellent physico-chemical and mechanical properties and with good strength/weight ratios in the finished products. However, the fabrication of high-strength metals consisting of these elements, using mechanical alloying and milling and cladding-type metal working, generally involves long-term processing conducted under extreme conditions using special facilities. The present study demonstrates the very rapid synthesis of a metal matrix nanocomposite (MMNC) of the Al-Mg system which was achieved by stacking metal disks of the two pure metals and processing by high-pressure torsion at ambient temperature for 10 turns. An exceptionally high hardness was achieved, similar to many steels, through rapid stress-induced diffusion of Mg and the simultaneous formation of intermetallic nano-layers and a nanostructured intermetallic compound with a supersaturated solid solution. This unexpected result suggests a potential for simply and expeditiously fabricating a wide range of MMNCs.
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Using high-pressure torsion to process an aluminum-magnesium nanocomposite through diffusion bonding
Kawasaki, Megumi,Ahn, Byungmin,Lee, HanJoo,Zhilyaev, Alexander P.,Langdon, Terence G. Cambridge University Press (Materials Research Soc 2016 Journal of materials research Vol.31 No.1
<▼1><B>Abstract</B><P/></▼1><▼2><P>Disks of commercial Al-1050 and ZK60A alloys were stacked together and then processed by conventional high-pressure torsion (HPT) through 1 and 5 turns at room temperature to investigate the synthesis of an Al-Mg alloy system. Measurements of microhardness and observations of the microstructures and local compositions after processing through 5 turns revealed the formation of an ultrafine multi-layered structure in the central region of the disk but with an intermetallic β-Al3Mg2 phase in the form of nano-layers in the nanostructured Al matrix near the edge of the disk. The activation energy for diffusion bonding of the Al and Mg phases was estimated and it is shown that this value is low and consistent with surface diffusion due to the very high density of vacancy-type defects introduced by HPT processing. The results demonstrate a significant potential for making use of HPT processing in the preparation of new alloy systems.</P></▼2>
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Haghdadi, N.,Zarei-Hanzaki, A.,Abedi, H.R.,Abou-Ras, D.,Kawasaki, M.,Zhilyaev, A.P. Elsevier Sequoia 2016 Materials science & engineering. properties, micro Vol.651 No.-
<P>This study demonstrates the evolution of microstructure and mechanical properties of a hypoeutectic Al-7Si-0.4Mg (A356) alloy processed by accumulative back extrusion (ABE) at temperatures ranging from 200 to 500 degrees C. ABE processing is one of the new severe plastic deformation techniques enabling one to produce relatively large ultrafine-grained materials in a cylindrical shape. One complete pass of ABE was estimated to introduce a reasonably homogeneous effective strain of similar to 3 as calculated by finite element analysis. Microstructural observation showed that globular alpha-Al primary phase was subdivided into fine substructures and Si particles having a fibrous shape were fragmented and spheroidized within the eutectic constituent through ABE processing. There was no evidence of homogeneous distribution of the fine Si particles in the alpha-Al phase after ABE. Mechanical testing at room temperature showed that both yield strength and ultimate tensile strength of the A356 alloy dramatically increased through ABE, especially at lower processing temperatures, as compared with the as-cast condition whereas there was no significant reduction in ductility at all processing temperatures. The experimental results were discussed with emphasis on the microstructure evolution involving dynamic recrystallization and deformation behavior including strengthening mechanisms and strain hardening in the Al-Si alloy. (C) 2015 Elsevier B.V. All rights reserved.</P>
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