Development of tensile-compressive asymmetry free magnesium based composite using TiO 2 nanoparticles dispersion
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In this present study, different volume percentages of titanium dioxide nanoparticles were added as dispersions in commercially pure magnesium using the blend-press-sinter powder metallurgy process followed by hot extrusion. The physically blended titanium dioxide nanoparticles dispersoid induced a significant grain refinement in the extruded magnesium matrix. Characterization of the mechanical properties revealed that the increasing volume percentage of titanium oxide nanoparticles dispersion was effective in enhancing the ductility of magnesium without disturbing the strength under tensile loading and enhancing the strength of magnesium without disturbing the ductility under compressive loading. The dominating deformation mechanism in pure magnesium was the dislocation slip, which was subdued by the tensile twinning deformation mechanism due to the increasing presence of titanium dioxide dispersion. The effect of shift in the dominating deformation mechanism was displayed by the elimination of tensile-compressive asymmetry in magnesium when dispersed with 1 vol% of titanium dioxide nanoparticles.
I. INTRODUCTION
Titanium dioxide is widely used in implant and healthcare applications1,2 due to its known biocompatibility in the anatase form3 despite some serious concerns.4 Reports suggest that titanium oxide improves the mechanical properties of metallic materials such as aluminum,5 magnesium,6,7 titanium,8 and zinc.9 Magnesium is one of the metallic elements which attracts interest for a wide range of applications from automobile to aerospace, owing to its lightweight and high specific mechanical properties, to biomedical owing to its good biocompatibility. Magnesium degrades in the human body fluid and forms a harmless compound dischargeable through urination. Hence, there is a renewed interest in recent years to use magnesium as a biodegradable implant in cardiovascular stent, bone fixation, and tissue engineering scaffolds.10,11 However, large scale of the wide-range application requires a further enhancement of strength with reduced tensile-compressive yield asymmetry and formability of magnesium using various ways including the advanced processing technique, alloying, and reinforcement. Reported studies show the limitation of biocompatible alloying elements10,11 on the mechanical properties of magnesium, where strengthening deteriorates the intrinsic limited formability. However, like many other oxide Contributing Editor: Yang-T. Cheng a) Address all correspondence to this author. e-mail: [email protected] or itsforfi[email protected] DOI: 10.1557/jmr.2017.430
nanoparticle dispersoids,12 titanium oxide nanoparticles showed potential in enhancing the strength and/or formability of magnesium without compromising each other.6,7 There is a potential for the development of a titanium oxide reinforced magnesium composite possessing a good combination of mechanical properties with tensilecompressive yield asymmetry. The incorporation method plays a major role in the exploitation of fine particle dispersion in the magnesiu
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