Study On Preparation Process And Properties Of SiCp/Al Matrix Composites

In this paper,by the means of mechanical stirring,SiC particles reinforced 2014 Al alloy composites was fabricated,and the best preparation process parameters were determined,specifically,the melt temperature was 630°C and the stirring speed was 350 rpm during stirring.After the addition of SiC particles,stirring was continued for 1 hour.The metallographic observation showed that in the prepared samples SiC particles were uniformly distributed and the interface was well-bonded.The grains of the matrix in as-cast SiC/2014 Al composites are coarse dendrites,and the average grain size is about 50 μm.After SiC particles are added,SiC is mainly distributed on the grain boundaries.The dendrite around the SiC transforms into nearly spherical grains.The average grain size is about 30 μm which shows grains are refined.After T6 heat treatment,the grains of the matrix in the composite material are converted from dendrites in the as-cast state to equiaxed grains.The main phase in the matrix is the α-Al phase,and some second phases,such as the θ phase(Cu Al2),the W(Cu4Mg5Si4Al)phase,and S(Cu Mg Al2)phase equal.Density measurements of composite materials decreased with the increase of silicon carbide content.The density of 2% vol SiC composite was 99.5%,that of 5% vol SiC composite was 98.95%,and that of 10% vol SiC composite was 97.51%.The mechanical properties of as-cast and heat-treated composites were tested.It was found that the microhardness of the as-cast composites increased by 16% from the substrate and reached 109.5 from 93.4.After heat treatment,the microhardness of the composites was higher than that of the matrix.Aluminum alloy increased by 46.94%,reaching 158.4 from 107.8.The maximum yield strength of the as-cast composite is 118.8 MPa,the maximum tensile strength is 176.2 MPa,and the maximum elongation is only 1.12%.After T6 heat treatment,the tensile strength of the composites containing 2%vol SiC reached 363.4MPa,the elongation reached 3.25%,and the yield strength of the composites containing 10%vol SiC was as high as 292.1MPa.For the fracture analysis of composite materials,it was found that the composite material was mainly brittle fracture.The fracture mechanism mainly includes three types of debonding of silicon carbide particles and matrix alloy,fracture of silicon carbide particles,and destruction of matrix alloy.