Characterization and strengthening mechanism of SiC nanoparticles reinforced magnesium matrix composite fabricated by ul
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Xiaojun Wang and Kun Wu School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001, People’s Republic of China (Received 4 April 2017; accepted 4 May 2017)
SiC nanoparticles reinforced magnesium matrix composite was fabricated by ultrasonic vibration assisted squeeze casting. Since ultrasonic device could meet the use requirements according to theoretic calculation, uniform dispersion of SiC nanoparticles was expected to achieve. The grains of the composite were refined compared with the AZ91 alloy, which was related to the increase of nucleation sites during solidification and Zenner pinning effect caused by SiC nanoparticles. With increasing the ultrasonic power, grain size of the composite changed no obviously while the morphology of b-Mg17Al12 phase was significantly affected. The ultimate tensile strength, yield strength, and elongation to fracture of the composites fabricated under different ultrasonic powers were simultaneously improved compared with the AZ91 alloy. The increase of yield strength could be attributed to Hall–Petch strengthening and Orowan strengthening for the present composites. Theoretical value of the yield strength obtained by the square root method was close to the experimental value.
I. INTRODUCTION
Owing to the low density and high specific mechanical properties, pure magnesium and its alloys have considerable potential for various engineering applications in automotive, aircraft industries, and electronics industries.1–3 However, there are several limitations of magnesium such as low ductility, high corrosion rate, poor creep, and abrasion resistance.4 To overcome these limitations, substantial efforts have been implemented to produce newly developed magnesium alloys and magnesium matrix composite by the addition of different type/size of reinforcements.5,6 The addition of ceramic particles to the magnesium matrix has been shown one of the possible methods, in addition to alloying treatment. The shape, size, and distribution of the ceramic particles and their interface compatibility with the matrix could affect resultant properties of the developed magnesium matrix composite. Studies have shown that the mechanical properties of the nano-sized particles reinforced magnesium matrix composites with a low volume fraction were comparable or even superior to that of micron
Contributing Editor: Jürgen Eckert a) Address all correspondence to this author. e-mail: [email protected], [email protected] DOI: 10.1557/jmr.2017.202
size particles reinforced composites with similar or higher volume fraction.7 Nano-sized particles reinforced magnesium matrix composites are currently fabricated by liquid based or solid based processing techniques, which are similar to micro-sized particles reinforced magnesium matrix composites. For the solid based processing such as powder metallurgy, the metal powders, and nano-sized particles with reasonable composition were mixed by mechanical alloying or simple blending.8,9 Secondary processing is necessary to further consolidate
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