Study On Microstructure And Properties Of SiC/2009Al Composites Prepared By Powder Metallurgy

SiC reinforced aluminum matrix composites have high specific strength,high specific modulus,high thermal conductivity,low density,low thermal expansion coefficient,wear resistance,fatigue resistance and other excellent properties,and are widely used in aerospace,automotive,electronics and other fields.SiC/2009 Al composites were prepared by powder metallurgy.The influence of aluminum powder particle size and hot pressed temperature on the microstructure and mechanical properties of the materials were investigated.The microstructure of the materials was observed and analyzed by metallography,X-ray diffraction,scanning electron microscope and electron probe.The experimental results show that the particle size of aluminum powder greatly affects the distribution uniformity of SiC particles.Too large aluminum powder size will lead to serious agglomeration of SiC particles,reduce the degree of material alloying,reduce the bonding strength of SiC/Al interface,and reduce the mechanical properties of the material.Hot pressed temperature also has a significant impact on the microstructure and properties of materials.Too high hot pressed temperature will cause strong interface reaction to generate insoluble coarse phase,which is harmful to the material properties.In view of the shortcomings of traditional powder metallurgy,such as the preparation cost is high,the preparation efficiency is low,and the process is complex.The cold isostatic pressing + press-free sintering process was used to prepare SiC/2009 Al composites instead of cold pressing billet + vacuum hot pressing,the influence of sintering temperature on the microstructure and properties of materials was also emphatically explored.The experimental results show that the sintering temperature is too low,even after extrusion,the bonding between reinforcement and matrix is very poor,SiC does not play the load transfer strengthening,there are a lot of pores in the material,the density is very low,and the material performance is very poor;With the increase of sintering temperature,the properties and density of the materials are on the rise,but there is a big gap with the properties of hot pressed materials;High sintering temperature will produce a large amount of liquid phase,resulting in the loss of alloy elements,reduce the effect of solid solution strengthening,so that the strength of the material decreases.620 is the best sintering temperature,at which the strength and plasticity of the material reach the maximum,but the density and interface bonding strength of the material need to be further improved.In order to further improve the density and performance of materials,high-energy ball milling method was used for ball milling granulation,so that the reinforcement particles and matrix alloy were well combined in the ball milling process.The influences of ball milling time,ball diameter and stearic acid content on the powder morphology after ball milling were investigated,and the ball milling powder under the optimal parameters is selected to prepare the composite.The experimental results show that uniform near-spherical particles can be prepared by using large diameter grinding ball milling for 30 min without stearic acid.The density of the composite material is significantly improved by pressureless sintering,cold isostatic pressing and extrusion of the powder particles,the SiC/Al interface bonding strength is also greatly improved.The yield strength and tensile strength of the materials are both increased by about 10%,and the plasticity of the materials is slightly reduced,but the decline is very small.It can be seen that the ball milling granulation method can solve the main problems existing in the cold isostatic pressing + press-free sintering process.On the basis of improving the preparation efficiency and reducing the production cost,the high performance 15%SiC/2009 Al composites can be prepared.