| In recent years, since the particle reinforced not only has low density, high specificstrength, specific stiffness, good wear resistance, low thermal expansion coefficient, goodthermal conductivity, etc, but also has low, simple preparation, easy casting complex shapeparts and isotropic etc, and its application prospect is broad, has become one of theresearch hotspots in the field of composites. Among them, the silicon carbide(SiCp)reinforced aluminum matrix composites has been applied in the fields such as aerospace,automotive, electronic. But currently there are still some problems in preparation ofSiCp/Al composites by casting, limiting its development. Such as the dispersion of SiCpinmatrix, the wetting between SiCpand aluminum matrix, the interface bonding betweenSiCpand aluminum matrix and so on. Therefore, this study tried to solve these problems.We have explored the influence law of different surface pretreatment (including pickling,oxidation, tetanizing), the size and volume fraction of SiCpto the microstructure andproperties of SiCp/2014Al composites. It has provided the experimental basis and datasupport to develop high-performance SiCp/2014Al composites with evenly SiCpdispersionand good interface bonding.In this ariticle, we prepared the SiCp/2014Al composites by stirring casting with thedifferent SiCpsurface pretreatment of pickling, oxidation and titanizing. The SiCpsize andvolume fraction that we used were5m,10m,15m and2%,4%,6%. We studied theeffects of SiCpsurface pretreatment, particle size and volume fraction on themicrostructure and property of composites. The main research results of this article are asfollows:1. Revealed the phase composition and morphology of silicon carbide particle withdifferent surface pretreatment: the surface of pickling SiCp was clean with the sharpedges and corners; the surface of oxidizing SiCp generated a homogeneous SiO2layerwith the blunt edges and corners; the surface of titanizing SiCp generated ahomogeneous Ti5Si3layer with the blunt edges and corners.2. Found the rule of the distribution of SiCpwith different surface pretreatment fromhomogeneous to inhomogeneous, from intracrystalline to grain boundary, the reunionphenomenon from mild to severe, the interface bonding between SiC and Al fromstrong to weak were: titanizing SiCp→oxidizing SiCp→pickling SiCp.3. Revealed the order from high to low of the tensile strength at room temperature of 15m2vol.%SiCp/2014Al with different SiCpsurface pretreatment was:titanizingSiCp(575MPa)→oxidizing SiCp(562MPa)→pickling SiCp(545MPa); their tensilestrength at high temperature(220℃) was slightly different, the order from high to lowfor their plastic was: itanizing SiCp(10.2%)→oxidizing SiCp(9.8%)→picklingSiCp(7.8%).4. Revealed the influence law of SiCpsize and surface pretreatment to the dispersionbehavior of SiCpin composites and the tensile properties at room temperature and hightemperature.(1) The influence law to the dispersion behavior of SiCp: the larger the SiCpsize is, themore homogeneous the dispersion of SiCpis. When the SiCpsize is15m, thedispersion of SiCpis the most homogeneous with no obvious reunion phenomenon;When the SiCpsize is10m, there is a small amount of reunion phenomenon; Whenthe SiCpsize is5m, the dispersion of SiCpis the worst homogeneous with no seriousreunion phenomenon. The dispersion of titanizing SiCpis better than The dispersion ofoxidizing SiCpin the same size, especially in a small size it is more obvious, and eventhe the dispersion of5m titanizing SiCpis better than the dispersion of10moxidizing SiCp.(2) The influence law to tensile properties at room temperature and high temperature: Atoom temperature, the tensile properties of SiCp/2014Al composites increased with theincrease of SiCpsize. At the same time, when SiCphas the same size, the tensilestrength with titanizing SiCpis higher than the tensile strength with oxidizing SiCp.When the volume fraction of SiCpis4%, their room temperature tensile strength are:524MPa (5m titanizing),507MPa(5m oxidizing);536MPa (10m titanizing),514MPa(10m oxidizing);548MPa(15m titanizing),545MPa(15m oxidizing). Underthe high temperature(220℃), the tensile strength increased with the increase of SiCpsize. Compared to oxidizing SiCp, the tensile strength of composites with tetanizingSiCpwas slightly low, the fracture strain was slightly high.5. Revealed the influence law of the volume fraction of titanizing SiCp to the dispersionbehavior, tensile properties at room temperature and high temperature.(1) The influence law to the dispersion behavior of SiCp: The higher the volume fraction,the more difficult the dispersion. Under the same size, when the SiCpvolume fractionare2%and4%, it has mild reunion phenomenon and the part distribution of SiCpis inthe intracrystalline. When the SiCpvolume fraction is6%, it has serious reunionphenomenon and the distribution of SiCpis main in the grain boundary with individual SiCpin the intracrystalline.(2) The influence law to tensile properties at room temperature: when the SiCpvolumefraction were2%and4%, the tensile properties of SiCp/2014Al composites increasedwith the increase of volume fraction, the tensile strength decreased when the volumefraction was6%. It had the highest tensile strength when the volume fraction was4%,they were524MPa(5m SiCp) and536MPa(10m SiCp).(3) The influence law to tensile properties at high temperature: when the SiCpvolumefraction were2%,4%and6%, the tensile properties of SiCp/2014Al compositesincreased with the increase of volume fraction, it had the highest tensile strength whenthe volume fraction was6%, they were308MPa(5m SiCp) and320MPa(10m SiCp).6. Revealed the main reasons of the room strength and plasticity of composites withtitanizing SiCpwas higher than the composites with oxidizing SiCpand pickling SiCpwere that homogeneous distribution of SiCp, most SiCpwere in the intracrystalline,reunion phenomenon was mild, and the interface bonding was good between SiCp-Al. |
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