Experiment Of Preparing Al-Ti Master Alloy By Aluminum Melt Reduction

Grain refinement can improve the strength,plasticity and toughness of metal materials.Al-Ti master alloy,as a kind of grain refiner,can change the grain size of aluminum,and improve the quality of aluminum and aluminum alloy materials.In the present study,Ti Al₃ phase Al-Ti master alloy was prepared by reducing TiO₂ dissolved in electrolyte molten salt with aluminum electrolyte molten salt as reaction medium and liquid aluminum as reducing agent.This method has the characteristics of low-cost and efficient preparation.The main research includes the following:The dissolution amount and existing form of TiO₂ in Na₃Al F₆-Al F₃-Ca F₂ molten salt system were studied by isothermal saturation method,and the effects of stirring strengthening,dissolution time,molecular ratio of molten salt and temperature on the dissolution amount of TiO₂ were also investigated.The results showed that the dissolution rate of TiO₂ in stirring state is fastest and the dissolution amount is largest under the same conditions of temperature,dissolution time and composition of molten salt.At a temperature of 960?,the dissolution amount of TiO₂ increases with the extension of dissolution time,and the basic equilibrium time is 120 min,but the dissolution amount of TiO₂ decreases with the increase of molecular ratio of molten salt system.Furthermore,as the temperature of the molten salt increases,the amount of dissolved salt also increases.Titanium dioxide mainly exists in the form of TiO₂ phase and Ti FO₂ in the molten salt system.The feasibility of preparing Al-Ti master alloy with Al as reducing agent was analyzed by thermodynamic calculation.The results show that at the reduction temperature of 298?1200 k,TiO₂ can be reduced by aluminum melt,and can produce Ti Al₃ and Al Ti two different aluminum-titanium intermetallic compounds.Moreover,the Ti Al₃ is most easily formed.Al-Ti master alloy was prepared by aluminothermic reduction with TiO₂ as raw material in Na₃Al F₆-Al F₃-Ca F₂ molten salt system.The effects of reduction conditions,such as dispersed aluminum,aluminum proportion,reduction time,reduction temperature,TiO₂concentration and the way of adding aluminum,on the particle size and morphology of Ti Al₃ in Al-Ti master master alloy were studied.The results show that the shape of Al-Ti master alloy prepared by adding 1.0 mol of dispersed aluminum is more regular;when the aluminum ratio is 1.8,the proportion of Ti Al₃ particles of 10-30?m is the highest;as the reaction time increases and the temperature increases,the proportion of Ti Al₃ particles of 10-30?m increases;When the concentration of TiO₂ is 4%,it not only ensures the nucleation of Ti Al₃,but also the growth of Ti Al₃ grains.When aluminum is added in batches,the aluminum added for the first time is mainly used for the nucleation of Ti Al₃,and the aluminum added for the second time is mainly used for the growth of Ti Al₃ grains.The suitable process parameters for preparing Al-Ti master alloy by aluminothermic reduction in molten salt system are as follows:reduction temperature960?,aluminum proportion 1.8,TiO₂ concentration 4%,reduction time5 min and dispersed aluminum 1.0 mol.The XRD and SEM-EDS tests of the Al-Ti master alloy prepared by thermite reduction showed that the phases were mainly Al and Ti Al₃;Ti Al₃ was lumpy and uniformly distributed.