| Aluminum alloy material is one of the most widely used non-ferrous materials in modern industry,with the acceleration of the pace of modern industrial development,the requirements for the performance of aluminum alloys are also increasing.Grain refinement is a method that can simultaneously improve the strength,hardness and plastic toughness of materials.It not only improves the material quality,but also improves the mechanical properties and processing properties of materials,and thus has received extensive attention and application.There are many methods for refining grains in industrial production,but the most economical,effective,and common method is to add intermediate alloy fine grains to the aluminum melt.In this paper,Al-Ti-C master alloys were synthesized by arc reaction using industrial pure aluminium,graphite powder and potassium fluorotitanate as raw materials.The microstructures and phase compositions of Al-Ti-C master alloys were studied by means of optical microscopy(OM),X-ray diffraction(XRD),scanning electron microscopy(SEM)and energy dispersive spectrometer(EDS)under different experimental conditions,such as changing raw materials and current,temperature of liquid aluminium,holding time and the proportion of carbon and titanium,and to explore the optimum process parameters for preparing Al-Ti-C master alloy.The results show that the phase of the Al-Ti-C master alloy synthesized by arc is mainly composed of ?-Al,Ti Al3 and Ti C.The instantaneous arc generation can form a local high temperature zone in the melt of aluminium,provide more heat,promote the wetting of carbon and aluminium melt,and make Ti C particles easier to form in the melt.The Al-Ti-C master alloy synthesized by arc is composed of K2 Ti F6 powder as titanium source and graphite powder after surface pretreatment as carbon source.K2 Ti F6 can react with aluminum liquid to generate a large amount of heat,which promotes the synthesis reaction of Ti Al3 and Ti C.Under the same experimental conditions,graphite powder can remove the oxide layer on the surface of graphite after surface pretreatment,eliminate the hydrogen bond formed between graphite particles,alleviate the graphite agglomeration phenomenon in liquid aluminium,increase the dispersion between graphite particles,improve the wettability between graphite and aluminium melt,andpromote the reaction between graphite and Ti atoms in melt to produce Ti C.The results show that the process conditions such as current,reaction time,temperature of molten aluminium and Ti/C have significant effects on the morphology and quantity distribution of Ti Al3 crystal.Under the conditions of current 70 A,reaction time 10 min,temperature of molten aluminium 800 C and Ti/C 6:1,the diameter of Ti C particles in Al-Ti-C master alloy is small,and the distribution of Ti Al3 particles is fine and uniform.Al-Ti-C master alloy prepared by the optimum process(holding time10 min,current 70 A,liquid aluminium temperature 800 C and Ti/C 6:1)was used to refine industrial pure aluminium.The effects of Al-Ti-1C master alloy addition and holding time on refinement effect of industrial pure aluminium were studied.The results show that the Al-Ti-1C master alloy synthesized under arc action has good refining properties.The best refining effect of industrial pure aluminum is obtained when the addition of Al-Ti-1C master alloy is 0.3% and the holding time is 20 minutes.In order to further promote the wetting of graphite and liquid aluminium,Al-Ti-C master alloys were synthesized by adding different amounts of rare earth Ce in the preparation of Al-Ti-C master alloys.The effects of the amount of rare earth Ce on the phase composition and microstructure of Al-Ti-C-Ce master alloys were studied.The results show that the main constituent phases of Al-Ti-C-Ce master alloy are ?-Al,Ti Al3,Ti C and Ti2Al20 Ce.When rare earth Ce is added to the Al-Ti-C master alloy,the number and morphology distribution of the second phase particles can be changed.When the addition amount of rare earth Ce is 0.5%,Ti Al3 in the Al-Ti-C-Ce intermediate alloy The particles are evenly distributed and have a small block shape.The Ti C particles have the smallest diameter and the largest number.Al-Ti-C-Ce master alloy(0.5% rare earth Ce)was prepared to refine industrial pure aluminium.The effect of the addition amount of Al-Ti-C-Ce master alloy on the refining effect of industrial pure aluminum was studied,and the difference of refining effect between Al-Ti-C and Al-Ti-C-Ce master alloys was compared.The results show that the refinement effect of Al-Ti-C-Ce master alloy is better than that of Al-Ti-C master alloy.The refinement effect of industrial pure aluminium is the best when the content of Al-Ti-C-Ce master alloy is 0.4%.Al-Ti-C and Al-Ti-C-Ce master alloys prepared under arc action have good refining effect on industrial pure aluminium,but Al-Ti-C-Ce masteralloys have better refining performance due to the alloying and modification of rare earth Ce. |
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