Study On The Interface Reaction And Wettability Of C_f/Al-Si Composites

The Gibbs free energy and critical nucleation size of Al4C3and SiC generated werecalculated from the the perspective of thermodynamics in this article. It is shown that:the Gibbs free energy and the critical nucleation size of of Al4C3increase with thecontent of Si in Al-Si alloy, while that of SiC decrease with higer Si content,whichindicates that Si element in Al-Si alloy can inhibit the generation of Al4C3andaccelerate the interface reaction between Si and Carbon fiber. Al20Si alloy was used forpreparing the Cf/Al20Si composites by pressure infiltration to replace the Al4C3production with SiC on the interface between Carbon fiber and Aluminum alloy.Cf/Alpurecomposites was also prepared by the same method as the comparison withCf/Al20Si composites.The Cf/Alpureand Cf/Al20Si composites were heat at750℃for1h,2h and3h,making sure that the reaction between Carbon fiber and Al-Si alloy was completelyaccomplished. The optical microscope, scanning electron microscope,transmissionelectron microscope and X-Ray Diffraction were used to analyse the composites afterheat treatment. Accordiong to the results, the percent of Al4C3in Cf/Al20Si compositesis10wt.%, lower than17wt.%in Cf/Al composites, and there is also10wt.%SiCgenerated in Cf/Al20Si composites. Therefore, a higher Si content in Al alloy is good forthe formation of SiC, reducing the content and size of Al4C3in Cf/Al composites, whichis well agreed with the thermodynamics calculation result.The interface bonding strength of Cf/Alpureand Cf/Al20Si composites wasmeasured by three point bending test along the transverse direction of Carbon fiber. Thebonding strength of Cf/Alpurewith clean interface is53.89MPa, which is improved to64.80MPa in Cf/Alpurecomposites and63.65MPa in Cf/Al20Si composites after heattreatment at high temperature. It is well demonstrated that the interface production(Al4C3and SiC) can improve the interface bonding strength of Cf/Al-Si composites.The wettability of Cf/Alpureand Cf/Al20Si was also studied in this article. Thecontact angle of Cf/Alpureand Cf/Al20Si was calculated by modified Young’s equation.The contact angle of Cf/Alpureand Cf/Al20Si between1023K and1423K was measuredusing sessile drop method. The results of experiment were in good accordance withcalculation of modified Young’s equation. The initial contact angle of Cf/AlpureandCf/Al20Si is about145to115with the temperature varing from1023K to1423K. Thecontact angle of Cf/Alpureand Cf/Al20Si decreases to70～60after interface reactionbetween Carbon fiber and Al-Si alloy with the extension of heat preservation time at1223K、1323K、1423K. It can be seen that Cf/Alpureand Cf/Al20Si have no big difference on reaction wettability. The Al2O3thin film on the surface of Al-Si alloyliquid has effect on the interfacial wetting behavior and it cracksbetween1170K and1275K temperature range.