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Effect of different sizes of balls on crystalline size, strain, and atomic diffusion on Cu-Fe nanocrystals produced by mechanical alloying

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Effects of ball diameter on the crystalline size, induced strain, and atomic diffusion in Cu-50%Fe immiscible alloy system have been investigated. Milling parameters affect atomic diffusion in binary or ternary systems separately. The aim of this research work is to prove the fact that ball diameter is an important parameter. It is shown that different diameters can change milling power, and consequently, the final crystalline size and atomic diffusion can alter. X-ray diffraction and scanning electron microscopy were used to analyze the effect of ball diameter. It is shown that the strain increases from 0.0025 to 0.0052, while the crystalline size decreases to 18 nm.

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Published 01 January 2012
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Language English
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Vaeziet al.Journal of Theoretical and Applied Physics2012,6:29 http://www.jtaphys.com/content/6/1/29
R E S E A R C HOpen Access Effect of different sizes of balls on crystalline size, strain, and atomic diffusion on CuFe nanocrystals produced by mechanical alloying 1* 22 Mohammad Reza Vaezi, Seyed Hesam Mir Shah Ghassemiand Ali Shokuhfar
Abstract Effects of ball diameter on the crystalline size, induced strain, and atomic diffusion in Cu50%Fe immiscible alloy system have been investigated. Milling parameters affect atomic diffusion in binary or ternary systems separately. The aim of this research work is to prove the fact that ball diameter is an important parameter. It is shown that different diameters can change milling power, and consequently, the final crystalline size and atomic diffusion can alter. Xray diffraction and scanning electron microscopy were used to analyze the effect of ball diameter. It is shown that the strain increases from 0.0025 to 0.0052, while the crystalline size decreases to 18 nm. Keywords:Mechanical alloying, CuFe, Immiscible systems, Diffusion, Nanocrystals, WilliamsonHall PACs:81.20.Ev, 66.30.h, 61.46.Hk, 61.05.cp.
Background In recent years, immiscible systems have been of great interest, owing to the nonequilibrium structure trans formation and technological merits related to them. However, the mechanisms for structure transformation in immiscible systems during the process of alloying are still under debate [1]. The repeated fracturing and cold welding of powder particles during mechanical alloying (MA) process induce a reaction between solid compo nents of the initial mixture [2]. Mechanically stored en thalpy caused by internal strains due to a very high density of dislocations and a large fraction of grain boundaries can serve as a driving force for the formation of alloy [3]. A special advantage of MA is to produce alloys of immiscible elements such as CrCu [4], AgCu, CuFe [5], CuW [6,7], and AlPb [8], which are difficult to produce by conventional methods because of the problem of heavy segregation while solidifying from the liquid phase. In such cases, MA provides a route to obtain a homogeneous distribution in the solid phase [5,9,10]. During MA, ball energy transfers to the
* Correspondence: m_r_vaezi@merc.ac.ir 1 Division of Nanotechnology and Advanced Materials, Materials and Energy Research Center, Karaj 3177983634, Iran Full list of author information is available at the end of the article
entrapped powders and causes severe plastic deform ation, soit enhances the density of dislocations and pro motes the formation of excess vacancies [11]. On the other hand, pipe diffusion needs low temperature and a high strain rate or stress which are provided by MA [12,13]. These conditions together increase atomic diffu sion and consequently lead to the formation of a solid so lution of Cu (Fe). The most important and wellknown parameter which is still under investigation in most of re search works is milling time. The effect of other milling parameters such as milling speed [14], amount of process control agent [15], and balltopowder ratio (BPR) [16] has also been investigated. Our recent research [17] was focused on the optimization of mechanical alloying by finding the optimum level of milling parameters. Although these parameters are obviously effective, ball diameter seems to be the missed one. By using different mixtures of ball diameters, namely 15 and 10 mm, at the same BPR, we face two specific conditions. In the 10mm case, we have more balls and consequently more surfaces and effective impacts. In the 15mm case, although the rate of effective impacts decreases, the amount of trans ferred energy per collision increases which depends on the kinetic energy of the balls. The aim of the present study is to determine the effect of ball diameter on
© 2012 Vaezi et al.; licensee Springer. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.