Microstructure,Mechanical Properties And Corrosion Resistance Of ZnOnw Reinforced Mg Matrix Composites

Magnesium matrix composites have broad potential in the field of engineering application due to their advantages of high strength,high modulus and light weight.In order to further improve the comprehensive properties of magnesium matrix composites,especially the mechanical properties and corrosion resistance,whisker reinforced magnesium matrix composites have become a research hotspot in recent years.In this paper,Pure Mg and low rare earth Mg-2Gd alloy were selected as the matrix,and the four needle ZnO nanowhisker(ZnOnw)were used as the reinforcement phase.The lattice constant of ZnOnw is very close to Mg,and ZnOnw has the characteristics of high strength,high modulus,low thermal expansion and isotropy.Therefore,ZnOnw can be used as the ideal reinforcement phase for magnesium matrix composites.This paper designed and optimized the preparation process of magnesium matrix composites,which was uniformly mixed the powder by the mechanical ball milling,prepared the prefabricated block and combined with the semi-solid melting mechanical stirring process.Using this method,the xZnOnw/Mg and xZnOnw/(Mg-2Gd)(x = 0,0.1,0.5,1.0 wt.%)were successfully prepared.At the same time,through a series of experiments and characterization,the microstructure,mechanical properties and corrosion resistance of xZnOnw/Mg and xZnOnw/(Mg-2Gd)composites were systematically studied,which provided certain basis for the development and application of magnesium matrix composites.On the one hand,with the increase of ZnOnw content in the xZnOnw/Mg composites,the texture of the as-extruded composites was weakened gradually,the grain size was refined and the strength was continuously improved.When the amount of ZnOnw was 0.5 wt.%,the composite had optimal comprehensive mechanical properties.Compared with pure Mg,0.5ZnOnw/Mg composite yield strength increased by 67.9 %and the tensile strength increased by 28.2 % without reduced plasticity.In addition,0.5ZnOnw/Mg composite also showed optimal corrosion resistance.However,with the continuous increase of addition amount.Excessive ZnOnw(1.0wt.%)was easy to form obvious clusters in the matrix,which was not conducive to further improvement of mechanical properties and also leads to the decrease of corrosion resistance.On the other hand,ZnOnw and its clusters in the xZnOnw/(Mg-2Gd)composites were distributed along the extrusion direction,which was similar to the xZnOnw/Mg composites.With the increase of ZnOnw content in the xZnOnw/(Mg-2Gd)composites,the grain size was gradually refined and the strength was gradually improved with the Schmid factor of the substrate reduced.The 0.5ZnOnw/(Mg-2Gd)had the best mechanical properties.Compared with Mg-2Gd alloy,the yield and tensile strength of the 0.5ZnOnw/(Mg-2Gd)composite were increased by 91.5% and 36.2% respectively,but the plasticity was not significantly decreased.At the same time,the main factors affecting the corrosion resistance of xZnOnw/(Mg-2Gd)composites were grain refinement and dispersion of ZnOnw.In the 0.5ZnOnw/(Mg-2Gd)composite,the fine grain size,as well as the uniform distribution of the ZnOnw and second-phases were conducive to uniform corrosion,which significantly improved the corrosion resistance.