| With the development of society,the demand for high performance and light materials in automotive parts and aerospace,aviation and other industries is booming.Metal Matrix Composites(MMC)which are prepared by adding ceramic reinforcements to magnesium or magnesium alloys,could combined the best of each materials which is propitious for the development of magnesium alloy in widen application fields.Undoubtedly,exploring a highly efficient and cost-effective method to prepare high-performing magnesium alloy composites is exigent.Among them,the particulate reinforced magnesium matrix composite has attracted considerable attention by combining the advantages of low cost,easy to manufacture and isotropy.In addition,the Al2O3 ceramic sphere has high strength,strong corrosion resistance and good thermostability.Although there are various preparation methods of Al2O3 ceramic spheres reinforced magnesium matrix composites and all of them have their own character,we use the infiltration casting method to form the composites by considering the poor wettability between the Al2O3 ceramic sphere.What' more,the method of infiltration casting is also beneficial to obtain the composite with high volume fraction of reinforcement.In this work,we successfully prepared the Mg/Al2O3 composite and AZ91D/Al2O3 composite which were reinforced by different diameter(2 mm,3 mm,4 mm)of ceramic spheres based on pure magnesium and the AZ91 D matrix by infiltration casting method.The structure of the magnesium matrix composite and the interface between matrix and reinforcement were observed and characterized by scanning electron microscope(SEM).Compression tests in room temperature on the magnesium matrix composites were also conducted and relevant test data were examined to verify the changing relationship between the diameter of the Al2O3 ceramic sphere and compression performance of the composites.The failure mechanism of composites in compression tests is researched by the analysis of SEM fractographies.The composite with the certain size ceramic sphere was selected as the research object in this paper,and the quasi-static high temperature compression and analysis to fracture morphology were employed to analyze the material.As a result,the influence law of the temperature on compression properties of Al2O3 reinforced Mg MMCs and the mechanism of compression failure at high temperature were studied.The corrosion resistance properties of composites were studied by metallic material uniform corrosion method.The Na Cl solution with 3.5% mass fraction is set as corrosion environment in the experiment.The corrosion behaviors of composites with different matrix were revealed by the appearance of corroded regions.This paper reviews a comprehensive study of Al2O3 reinforced magnesium matrix composites and the results are as follows:1)In this work,we successfully fabricated the Mg/Al2O3 composites and AZ91D/Al2O3 composites by infiltration casting method which process was optimized.The reinforcement,ceramic spheres,is distributed homogeneously in matrix.It can be observed that the density of the magnesium matrix composites increases with the ceramic spheres size.with the increasing of volume fraction.In addition,the interface between reinforcement and matrix alloy is very clean and there is no interfacial reaction in Mg/Al2O3 composite.For the AZ91D/Al2O3,the Al2O3 ceramic sphere has a rough surface and presents many protuberances in micro-structure.These protuberances were the nucleation site and the ? phase are nucleated preferentially at this region which is beneficial for the matrix is tightly bound to the ceramic sphere surface.The results show that the bonding between the ceramic sphere and the matrix is mechanical and metallurgical.2)The stress strain curves obtained in the experiments of quasi static compression exhibit not only the peak strength but also the specific strength of the Mg/Al2O3 composites and AZ91D/Al2O3 composites were higher than matrix alloy.Especially,whether peak strength or specific strength of the composites increased with the volume fraction of the ceramic sphere.when the materials were compressed at evaluated temperature,the peak strength and energy absorption capability of the composites would drop due to the matrix softening.As the temperature rises,both of the composite and the matrix alloy shown a decreasing trend.Usually,because of the degree of matrix softening relatively low in 200 oC and the ceramic sphere with high temperature resistant performance,the decrease trend of peak strength of composite is much lower than that of matrix alloy.When the temperature is up to 300 oC,the degree of matrix softening increased while the reinforcement effect of the ceramic sphere decreased result in the decreased range of the peak stress of the composite is in accordance with the matrix.3)The influence of corrosive environment on materials is researched by soaking the materials in Na Cl solution.Both of the matrix alloy and the composites exhibited a similar pitting corrosion.However,whether the Mg/Al2O3 composites or AZ91D/Al2O3 composites shown corrosion resistance property compared with the matrix alloy due to their good interface bonding and good anti-corrosion properties of Al2O3 ceramic sphere. |
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