Effects Of Process Parameters And Aluminum Addition On The Reaction System Of Iron-based Composites

In order to resolve the key problem of high cost in the development and application of iron-based composites, a new technology has been designed to produce iron-based composites in this paper. By the technology, it is possible to fabricate iron-based composites at low cost. Iron-based composites reinforced with Ti(C,N) particle and Al2O3 particle, were produced by powder metallurgy utilizing the thermit reaction and carbothermic reaction between ilmenite and graphite, aluminum. It made progress both in experimental investigation and theory calculation.The feasibility and reaction process of the technology were investigated and discussed by thermodynamic calculation and comprehensive thermal analysis (TG-DSC) technique in this paper. The effects of aluminum content, mill time, sintering temperature and holding time were also investigated by XRD analysis and TG-DSC technique.According to the present investigation, the following results were obtained. Fistly, Al2O3-Ti(C,N)/Fe composites can be synthesized by in situ carbothermic and thermit reduction using natural ilmenite as raw material. The results showed that the progress of reduction of ilmenite (FeTiO3) was firstly reduced intoα-Fe , intermediate product TixOy and Al2O3 by aluminum, then C and N continued to react with TixOy, and TiC1-yNy finally formed. Secondly, the results of XRD showed that after sintering at 1400℃for 4 hours and 1600℃for 2 and 4 hours, the reductive products of FeTiO3-xAl-(4-3x/2)C-2Fe (x=0.5,1.0,1.5,1.75,2.0) system were Ti(C,N), Al2O3 and Fe. AlN was found in the reductive products of FeTiO3-1.5Al-1.75C-2Fe system which sintered at 1400℃for 4 hours and 1600℃for 2 hours,and in FeTiO3-0.5Al-3.25C-2Fe system which sintered at 1400℃for 4 hours.Thirdly, the effect of aluminum content on reaction process was obvious. With the increasing of aluminum content, the start temperature of thermic reduction depressed and the start temperature of carbothermic reduction heightened. Fourthly, the effect of mill time on reaction products was not abvious. But high-energy ball milling can result in smaller granularity of ilmenite, graphite and aluminum powder, larger specific surface area and form tighter combination as well as large quantity of defects and strains so that the powder reaction activation energy can be decreased, the kinetic barrier of product formation is lowered.