| In this experiment,SiCp/ZL109 composites with different SiCp content were prepared by stir-casting process using the equipments made by ourselves.The effect of different SiCp content on the mechanical properties,friction behavior and microstructure were investigated using X-ray,OM,SEM,hard test and wear test.We also discussed the new path which can improve the combination property of SiCp/ZL109 by studying the effect of minor Sc and Zr on the microstructure and property of ZL109 alloy.The experiment results were analyzed and discussed theoretically.Several conclusions can be summarized as follows:1.In this experiment,three kinds of SiCp/ZL109 composites with different SiCp content were prepared by stir-casting process.The accurate parameter is:On 780℃,smelting ZL109 alloy;On 700℃, adding SiCp by stir-casting process,the mixing speed is about 680～780r/min and endurance period is 60min.On 740℃,pouring.The percentage composition of SiCp are tested by X-ray,the mass percent of SiCp of three kinds of SiCp/ZL109 composites is 8%,10%,12%.2.The result of mechanical properties and friction properties test show that:the hardness,friction factor and wear-resistance propery of the matrix are higher than ZL109 and with the increase of SiCp content, the properties increase too.3.SiCp is taking double-response during the friction test.Before fracturing,SiCp protects Al-Si matrix from sticking friction;When SiCp brakes,it generated many hard points and resulted in grain-abrasion.4.SEM investigating show that sticking friction,Oxidize friction and grain-abrasion are all taking effect in the friction procsse of SiCp/ZL109 and the sticking friction is the most important friction form.The friction pattern is that:Sticking friction happening on the surface of matrix alloy→SiCp protect matrix alloy from wearing→SiCp fragmenting→Sticking friction,Oxidize friction and grain-abrasion happening on the friction surface simultaneity.5.The addition of minor Sc,Zr in SiCp/ZL109 can refined the matrix's grains and improve the strength obviously.Compare with the typical as-cast structure of SiCp/ZL109.During the friction braking process Sc,Zr retardate the motion of dislocation and depress the plastic yield of microne on the matrix's surface.Then this new composite's friction factor and wear-resistance propery are higher than the typical one. |
