Effect of ceramic nanoparticle reinforcements on the quasistatic and dynamic mechanical properties of magnesium-based me
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Yulong Li Department of Aeronautical Structure Engineering, School of Aeronautics, Northwestern Polytechnical University, Xi’an, Shannxi, 710072, People’s Republic of China
Jinling Liu and Linan Anb) Advanced Materials Processing and Analysis Center, University of Central Florida, Orlando, Florida 32816 (Received 25 October 2012; accepted 24 January 2013)
We have investigated the microstructure, the quasistatic and high-rate mechanical properties of magnesium (Mg)-based metal-matrix composites (MMCs) reinforced with nanoparticles, also termed as metal-matrix nanocomposites (MMNCs), in this case reinforced with nanoparticles of b-phase silicon carbide (b-SiC) the volume fraction ranging from 5 to 15 vol%. The yield and the ultimate strength increase with reinforcement volume fraction up to 10 vol% nanoparticles. MMCs with micrometer-sized SiC particles have higher yield strength than their MMNC counterparts, whereas the ultimate strength shows the opposing trend, suggesting greater strain hardening in the MMNCs. Transmission electron microscopy shows that the average interparticle distance decreases with increasing SiC vol%. Recrystallization was reported as completed during sintering at 575 °C [R.D. Doherty et al., Mater. Sci. Eng. A, 238, 219 (1997)], but dislocations might be generated due to thermal expansion mismatch of Mg/SiC during cooling. The majority of Mg-grains below 20 nm remain around the nanoparticles. As such a reverse volume fraction effect takes place in 15 vol% nanoparticle-reinforced MMNCs, which off sets the strengthening advantage induced by the nanoparticles. I. INTRODUCTION
Magnesium alloys have found numerous applications such as in automotive, electronics and medical areas due to their extraordinarily high specific strength.1–4 More potential applications in many critical areas are yet to be identified in the short term. However, one of the stumbling blocks for the wider applications of Mg alloys is their low creep resistance. Also problematic are their relatively poor microstructural stability at elevated temperatures and the generally low corrosion resistance, as well as their usually poor tensile ductility due to the hexagonal close-packed (HCP) lattice structure.5–8 The particular HCP lattice structure of Mg limits it to less than five independent slip systems, leading to undesirable brittle behavior of its polycrystalline form. It has long been recognized that basal slip dominates the dislocation activities at ambient temperature and under ordinary loading conditions, though sporadic evidence for prismatic slip and even pyramidal slip has been reported.5,9–14
Address all correspondence to these authors. a) e-mail: [email protected] b) e-mail: [email protected] DOI: 10.1557/jmr.2013.16 J. Mater. Res., Vol. 28, No. 13, Jul 14, 2013
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Twinning has also been explored15–17 but the high stacking fault energy needs to be well addressed in the first place. Recent efforts show that severe plastic deformation such as equal channel angular extrusi
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