Study On The Preparation And Properties Of C_sf-SiC_NW/Al Composite

In this paper,the mixed powder of C and Si was prepared by high energy ballmilling.Then the mixed powder was made into slurry of ethanol and coated onto theM40J short carbon fiber.-SiC nanowires were synthesized on the surface of carbonfiber at1200C in argon. Csf-SiCNW/Al composite was fabricated by squeeze castingtechnique using the short carbon fiber with-SiC nanowires and6061aluminumalloy.And the volume fraction of carbon fiber was6%and10%and the correspondingvolume fraction of SiC were0.6%and1.2%.The phase,morphology,composition and crystal structure were charactered byXRD,SEM and TEM.The effect of diffierent milling process on the SiC nanowiregrowth was analysed.The thermodynamic of the growth process and mechanism werealso discussed.The mechanical properties of Csf-SiCNW/Al was studied bythree-point-binding and tensile test.The metallographic and fracture morphology wereobserved.The phase and microstructure in the composites were analysed.The effect ofSiC nanowire on the mechanical properties of Csf/Al composites was investigated.The slurry of mixed powder milled for24h was coated on the carbon fiber andheated at1200C for1h.A large amount of nanowires were observed on the surface ofcarbon fiber.XRD shows that the crystal structure of nanowires is-SiC.The diameter ofnanowires is20100nm and the length is several tens micrometer to several hundredmicrometer.There are two different kinds of morphology,which are straight andcurved.The synthesized naonowires has the “core-shell”structure,which has a uniformSiOxamorphous layer with the SiC core.In the core there are many stacking faults andtwins,leadeing to the serrated surface.The growth direction of SiC nanowires is <111>.There is a little amount of nanowires are bamboo-like or has a chain morphology withbeads.Some spherical particles were found at the end of nanowires,whose diameter are alittle larger than the nanowires.They play the role of melal catalyst in traditional VLSmechanism by absorbing SiO and CO.SiC precipitates when the concentration becomessaturated.Mechanical properties experiment shows that the introduction of SiC improves thestrength of the composites.For the composites with the same volume fraction of carbon fiber, SiC nanowires is favourable to increase the plasticity.When carbon fiber volumefraction reaches10%, the maximum binding strength of the composites with SiCnanowires after T6treatment is602MPa,which is improved by33%and the maximumtensile strength is374MPa,which is increased by18.6%,when they are compared withthe composites without SiC nanowires.The placticity of composite is greatly improvedby introducing the SiC nanowires.The fracture observation suggests that the surface of carbon fiber the didn’t changesignificantly.The carbon and the matrix are mechanicaly bonded.There were somecarbon debonded and pull out of the matrix. The introduction of SiC nanowires gain theplacticity of the composite,leading to obvious micro plactic deformation and fracturecharacteristics.