Study On The Microstructure And Properties Of Mixed Particles Reinforced Aluminum Matrix Composites

SiC reinforced aluminum matrix composites is a new material, its quality is onlyabout one sixth of the traditional metal-based composite material and its controlledexpansion coefficient, good mechanical, thermal conductivity performance and highstrength ratio advantages. Mixed particles reinforced Al-30Si composites werefabricated by vacuum hot pressing plus sintering, which had reinforcing phasedistributed evenly, adjustable volume, and without full penetration during thepreparation of the high-temperature state, which avoided the interface occurs of theproblem of the excessive reaction between the casting method of the matrix and thereinforcing phase. The Al-30Si alloy powders and SiC particles have a little away froma thermal expansion coefficient, with small residual stress in the material, and multi-scale silicon phase was precipitated in vacuum hot pressing plus sintering process,which can reduce the coefficient of thermal expansion and thermal cycling stresssignificantly, increase the tensile strength of the material.The matrix was Al-30Si alloy powder and the reinforcement was SiC particles inthis subject,1000°C high temperature roasting (with different times)+washingtreatment of SiC particles were treated, SiC particle reinforced Al matrix compositeswere prepared by vacuum hot pressing plus sintering. The microstructures and fracturesurfaces of the materials were analyzed by SEM and EDS; The phase structure of thecomposite materials was analyzed by the D-8X ray diffraction; Density of the sampleswas measured using Archimedes method; and the tensile strength were examined bythe Shimadzu Ag-1250KN precision-universal testing machine; the melting point ofthe test material was examined in the DSC differential thermal analyzer; thecoefficient of thermal expansion was tested in the German NETZSCH DIL402PCdilatometer; Turner and Kerner theoretical models were employed to calculate thecoefficients of the thermal expansion.The affect of different SiC surface treatment of SiC were analyzed on the SiC particles distribution in the composites; the affect of SiC particle volume fraction andparticle size were studied on the tensile strength, density, coefficient of thermalexpansion and SiC particles distribution in the composites; the SiCp, Sip with thesubstrate binding interface mechanism were investigated.The result showed that the optimum ratio: SiC particle volume fraction was25%,particle size was13μm, the Al-30Si powder volume fraction was75%and particle sizewas8μm. The surfaces of the SiC powder miter were passivated, the roughness andmobility of the powder in the matrix were increased, distributed evenly, reducing thevoids generated in the material. SiC particle reinforced Al-Si matrix composites wereprepared. At this time, the tensile strength was190MPa, the thermal expansioncoefficient was10.8×10-6K-1, the densification was98.78%. The combination ofinterfacial phenomena was calculated and explained by theoretical thermodynamicmodel, interfacial chemical reaction and interface wetting principle. The results showthat the edges of SiC and Si were observed to be clean and sharp, indicating that nointerfacial reactions have occurred. three types of different orientation relationshipswere observed between the SiC and Al phase, with the SiC[011] parallel to theAl[011]、(111) SiC//(111)Al and (022) SiC//(022)Al，where a good semi coherentbonding exists between them.