Preparation and characterization of a novel solid solution of aluminum in tungsten carbide by mechanically activated hig
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anfeng Maa) and Wei Zhao Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China
Huaguo Tang, Changjun Zhu, and Shuguang Cai Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, People’s Republic of China; and Graduate School of Chinese Academy of Sciences, Changchun 130022, People’s Republic of China (Received 14 October 2005; accepted 23 January 2006)
In this work, a novel substitutional solid solution (W0.8Al0.2)C was synthesized by mechanically activated high-temperature reaction. X-ray diffraction was used for phase identification during the whole reaction process. Environment scanning electronic microscopy–field emission gun and energy dispersive x-ray were used to investigate the microstructure and the quantitative material composition of the specimen. (W0.8Al0.2)C was found to crystallize in the WC-type, and the cell parameters were a ⳱ 2.907(1) Å and c ⳱ 2.837(1) Å. The hardness of (W0.8Al0.2)C was tested to be 19.3 ± 1 GPa, and the density was 13.19 ± 0.05 g cm−3.
I. INTRODUCTION
Transition-metal carbides like tungsten carbide (WC) have long attracted interest due to their many interesting physical and mechanical properties.1 They exhibit high melting point, extreme hardness, low coefficient of friction, chemical inertness, oxidation resistance, and good electrical conductivity. On the other hand, however, pure WC has some inevitable shortcomings such as high density (15.63 g cm−3)2 and high material cost. Therefore, we decided to investigate whether some other metals could react with WC to form ternary carbides that could avoid the above shortcomings while retaining the high hardness of WC. Aluminum is lighter than tungsten metal, so the dissolution of Al into WC is expected to reduce its high density. In addition, aluminum is inexpensive compared with tungsten; thus, material costs of ternary carbide Al–W–C are surely less than that of WC. Unfortunately, because of the large differences of density and melting point between W and Al metal, it is very difficult to synthesize this ternary carbide through the
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Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/JMR.2006.0232 1700 J. Mater. Res., Vol. 21, No. 7, Jul 2006 http://journals.cambridge.org Downloaded: 13 Mar 2015
traditional high-temperature reaction of W, Al, and C elemental powders. In our previous paper,3 we reported that W0.8Al0.2 alloy could be synthesized by mechanical alloying. Moreover, W0.8Al0.2 has the same bodycentered cubic structure as W and is high-temperature stable up to 1400 °C. Therefore, it is possible for W0.8Al0.2 to be carbonized to prepare the substitutional solid solution (W0.8Al02)C as the reaction between W and C to form WC.4 In this paper, we present a simple and rapid method for synthesis of the novel substitutional solid solution (W0.8Al02)C and hope that this new synthetic method can be used in the development of other new compounds. Additionally, the reaction mechanism, crystal structu
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