Study On The Preparation Of Ti₅Si₃ Alloy By Molten Salt Electrolysis

Titanium alloy is a kind of functional material with high melting point,low density and excellent corrosion resistance,which has many applications in various fields.Ti₅Si₃has a high melting point（2130℃）in titanium-silicon alloys.It has great strength at1200℃,so it is a good high-temperature structural material.At present,the main method of preparing Ti₅Si₃ are arc melting and powder sintering metallurgy,etc.These methods not only need to preparation at high temperature,but also relatively complicated.The molten salt electrolysis（FFC method）has many advantages,only need lower temperatures,easy to operate,and hardly has pollution to the environment.In this thesis,based on FFC method,tabletting and sintering the TiO₂ and SiO₂powders to prepare cathodes,graphite rods as anodes.Investing the electrolysis process of cathode prepared under different processes,the conclusions as below:The preparation method of the cathode was studied.The study showed that when tableting pressure is 5 Mpa,the internal pores are higher.After the cathode is sintered at a higher temperature and a longer time,the crystal form of TiO₂ change from anatase to rutile.Improving the assembly method from drilling and binding samples to direct binding samples.Improve the overall strength of the cathode,which can satisfy the experimental conditions.The effect of cathode sintering conditions on electrolytic products was studied.Unsintered cathode has more impurities after electrolysis,the target product is hardly collected;the cathode sintered at 700℃has a slow electrolysis rate,and there are still unreacted intermediate products in the product;when the cathode sintered at1000℃,target phase was found in the product,the sintering temperature was determined to be 1000℃.The reaction process of preparing Ti₅Si₃ by FFC was studied.When the cathodes sintering at the same temperature,the amount of Ti₅Si₃ in the product increases obviously with the increase of electrolysis time.When the electrolysis time is the same,the cathodes sintering at the higher temperature,the current in the entire electrolysis process is heavy,the electrolysis is faster.When using a thicker cathode for electrolysis,it was found that the composition of the inside and outside products was inconsistent.The outside of the cathode was Ti₅Si₃ and Ti₂O₃,and the inside products were Ti₅Si₃,CaTiO₃ and Ti₂O₃,it is confirmed that the reaction is occurd from outside to inside.According to the products in different stages of electrolysis,the reaction process is determined as follows:SiO₂ is directly reduced to elemental Si;the reaction of TiO₂ is relatively complicated,at first,TiO₂ reduced to Ti₂O₃,and at the same time the intermediate product CaTiO₃ is generated,as the electrolytic reaction proceeds,CaTiO₃is then electrolyzed to Ti₂O₃,and finally Ti₂O₃ is electrolyzed to form Ti and then reacts with Si to form Ti₅Si₃.