Enhancing the tensile and ignition response of monolithic magnesium by reinforcing with silica nanoparticulates
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Low volume fraction (0.5, 1, and 2 vol%) SiO2 reinforced magnesium nanocomposites were synthesized using powder metallurgy technique followed by hot extrusion. The nanocomposites were studied for physical, microstructural, ignition, and mechanical properties to study the influence of nanoparticulate addition on monolithic magnesium. The grain size of the developed nanocomposites was observed to marginally decrease with the addition of SiO2 nanoparticulates with 2 vol% SiO2 addition resulting in a grain size of ;23 lm which is ;32% lower than that of pure Mg. The ignition temperature of pure Mg was enhanced with the addition of SiO2 nanoparticulates with Mg 2 vol% SiO2 nanocomposite exhibiting an ignition temperature of 611 °C (;20 °C greater than pure Mg and AZ31 alloy). Under room temperature tensile loading, Hall–Petch strengthening mechanism was the most dominant wherein the addition of SiO2 nanoparticulates to pure magnesium enhances the strength within 0–2 vol% range and ductility in 0–1 vol% range.
I. INTRODUCTION
Magnesium (Mg) has been investigated for almost 200 years initiated due to the excellent work of Sir Humphry Davy back in 1808.1 Mg is the sixth most abundant element in the earth’s crust accounting to ;2.5% of its weight.2 In addition to being the lightest structural material commercially available, properties like enhanced specific strength, excellent castability, excellent weldability, high thermal and electrical conductivity, high damping capacity, and recyclability make it an appealing material for wide spread industrial applications.3–6 However, its limited ductility at room temperature coupled with poor wear and corrosion resistance has narrowed its potential applications.7,8 In recent times, several attempts have been made to understand the behavior of Mg in several physiological environments.9,10 Several advancements in improving the corrosion behavior of Mg and Mg based alloys have been reported in the open literature.11,12 The HCP crystal structure of Mg strongly affects its plastic deformation behavior resulting in limited ductility at room temperature.13 In comparison with grain refinement through alloy development, addition of stable inexpensive low volume fraction nanoparticulates leading to dispersion strengthening can be a promising approach to enhance the mechanical properties of Mg-based materials.14 High ductility in Mg-based materials can be realized by the activation of nonbasal cross slip systems or twinning through the Contributing Editor: Michele Manuel a) Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2017.194
modification of texture by incorporation of nano-length scale secondary reinforcements.15 Hence, the nanocomposite technology has significant potential to enhance the mechanical response of Mg-based materials. The five major strengthening mechanisms for metal matrix nanocomposites (MMNCs) are16: (i) Orowan strengthening mechanism, (ii) Hall–Petch relationship, (iii) Forest strengthening, (iv) Taylor relationship, and (v) Load bearing
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