| Magnesium alloys are the lightest metallic structural materials and have been hailed as the 21st century's green materials for their superior performance.SiC particles have high strength,wear resistance,and low cost.In order to give full play to the advantages of both,to prepare a wear-resistant material with high strength,modulus,hardness and dimensional stability,it is necessary to compound the two.In this paper,magnesium alloy is selected as the matrix of composite materials,SiC particles are the reinforcing phase,and magnesium matrix composites are prepared by powder hot pressing process.Firstly,SiC powder was pretreated,and mixed powders with different SiC contents were mixed and ball milled.The effects of different time and rotating speed on powder uniformity were explored.After the cold pressed into a powder blank,the powder compact is then put into a sintering furnace protected by a vacuum atmosphere,sintered at 580? to 640 0C,and kept warm for 1 hour.Finally,the temperature was lowered to 500?,and hot pressing was performed at 15 MPa,20 MPa,and 25 MPa for 20 min to improve the compactness of the material.Using SEM,EDS and other testing methods,the effects of different sintering temperatures and hot-pressing pressure on the microstructure and properties of the composites were studied.The results show that when the mixing speed is 100r/min and the time is 2h,the SiC dispersion is not uniform;at 4h,it shows a slight black color and oxidation phenomenon,at 3h,the mixing material has no oxidation and there is a mechanical bonding phenomenon.Magnesium matrix composites have a SiC volume fraction of 15%,a sintering temperature of 580 ?,a hot pressing temperature of 500 ?,and a pressure of 20 MPa.The SiC particles are exfoliated.Holes appear in the material,the relative density of the material is 93.33%,and the porosity is 6.67%.At 610 0C,the material pores decrease,but the SiC has agglomerates,the relative density is 95.72%,and the porosity is 4.26%.At 620 0C,the interface between the SiC particles and the matrix is well-bonded,the SiC is uniformly dispersed,and the denseness is high.The relative density is 96.17%,porosity 3.83%;640 0C,the material delamination phenomenon,because the higher the temperature,magnesium self-diffusion faster,in some of the substrate deposited on the bottom of the material.The SiC volume fraction of the composite is 15%,the sintering temperature is 620 ?,and the hot-pressing temperature is 500 ?.During the pressureless sintering,a large number of holes appear in the material,the compactness is very low,the relative density is 76.67%,the porosity is 23.33%,and the pressure is 15MPa.At the time,the materials show a few holes,the interface is poorly bonded,the relative density is 92.24%,the porosity is 7.76%;when the pressure is 20MPa,the interface of the material is well-bonded,the compactness is good,the relative density is 96.17%,the porosity is 3.83%;when the pressure is 25MPa,a small amount of particles The SiC particles with larger diameter appear cracks with a relative density of 97.21%and a porosity of 2.7%.The mechanical properties of SiC particle reinforced Mg-based composites show that the flexural strength of the Mg-based composites is significantly improved.When the volume fraction of SiC particles reaches 15 vol.%,the flexural strength of the composites is the best,and it is brittle fracture.With the increase of SiC volume fraction,the hardness of the composite gradually increase,the hardness of the matrix alloy is 84.8 HV,the SiC volume fraction is 5%,the hardness is 93.51 HV,the hardness is 143.5 HV at 10%,and the hardness is 197.5 HV at 15%.The 20%hardness is 228.6 HV.The friction and wear curves of composites with different SiC volume fractions show that the average friction coefficient of the composites is lower than that of the matrix alloys after the addition of SiC particles,and decreases at volume fractions of 5%,10%,15%,and 20%,respectively.20.6%,31.6%,39%,and 48%,however,the friction stability of 15%SiC volume fraction is better than 20%. |
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