Nitride Nanoparticle Addition to Beneficially Reinforce Hybrid Magnesium Alloys
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IN line with typical composite logic, the function of nanoparticles in a metallic matrix is related to (1) nanoparticle-matrix reactivity and (2) nanoparticle distribution in the matrix. This is with regard to any material property of the nanocomposite, be it mechanical (crystallographic structure related) or functional (electronic structure related). In the case of magnesium alloys as an easily available lightweight and energy saving metallic matrix, the AZ series of magnesium alloys are characterized by: (1) low cost, (2) ease of handling, (3) good strength and ductility, and (4) resistance to atmospheric corrosion.[1] These qualities enable the common use of AZ series magnesium alloys.[1] Regarding magnesium nanocomposites, AZ31 has been surfacereinforced with C60 molecules[2] and multiwalled carbon nanotubes (CNTs)[3], using the friction stir processing technique. It was reported in this study that (1) particle MURALIDHARAN PARAMSOTHY, Research Fellow/Consultant, and MANOJ GUPTA, Associate Professor, are with Department of Mechanical Engineering, National University of Singapore, 9 Engineering Drive 1, Singapore 117576, Singapore. Contact e-mails: [email protected]; [email protected] JIMMY CHAN, Principal Engineer and RICHARD KWOK, Chief Technology Officer, are with Singapore Technologies Kinetics Ltd. (ST Kinetics), 249 Jalan Boon Lay, Singapore 619523, Singapore. Manuscript submitted April 23, 2012. Article published online October 5, 2012 METALLURGICAL AND MATERIALS TRANSACTIONS A
dispersion was good, and (2) hardening of the base matrix at the surface occurred. Also, SiO2 nanoparticles have been added to AZ61 using the same processing method.[4] In this case, the tensile elongation at 350 °C of selected composites was barely 100 pct at 1 9 103 s1 strain rate, but reached 350 and 420 pct at 1 9 102 and 1 9 101 s1 strain rates, respectively. It was consequently implied that high strain rate super-plasticity (HSRSP) was clearly exhibited based on the sufficiently uniform dispersion of SiO2 nanoparticles. Much of the existing representative research literature on solidification processed magnesium alloy nanocomposites indicates that (1) good nanoparticle distribution can be achieved in the magnesium matrix, and (2) better mechanical properties can be achieved due to the addition of nanoparticles.[5–9] However, most of the research literature currently addresses the addition of oxide or carbon based nanoparticles to magnesium alloys, as opposed to nitride based nanoparticle addition. The magnesium-oxygen strong affinity and magnesiumcarbon weak affinity (comparatively) are both well known in the context of magnesium composite processing. However, the affinity between magnesium and nitrogen regarding effects in magnesium nanocomposite processing (let alone solidification processing) is not known. Regarding the mechanical performance of a nanocomposite, it is important to understand the nanoparticle-matrix interactions during plastic deformation from mechanical experimentation. Regarding metal matrix nanocomposites
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