Experimental Study On Preparation Of Al-Ti Master Alloy By Sintering

Grain refinement can improve mechanical properties,corrosion resistance and thermal stability of the alloy.As commonly used grain refiners,Al-Ti and Al-Ti-B master alloys can change the grain size and improve the quality of Al.In this paper,Ti O₂ powder,Ca O and Al powder were used as the main raw materials.After mixing,pressing and sintering,Al₃Ti phase master alloy was prepared.This method has the advantages of low raw material cost,sufficient reaction,easy separation of slag phase and metal phase,and can prepare Al₃Ti phase intermediate alloy.The main research work is as follows:The feasibility of preparing Al-Ti and Al-Ti-B master alloys with Al as reducing agent was analyzed by thermodynamic calculation.The results show that at the reduction temperature of 298～3760K,aluminum reduces Ti O₂ to form?G_T^θ<0,the reaction can happen;From the perspective of thermodynamics,at the reduction temperature of 298～3389K,aluminum can reduce B₂O₃ to form Ti B₂,Al B₁₂ and other Al-Ti-B master alloys,in which the?G_T^θvalue of Ti B₂ is the smallest.The effects of sample pressure,sintering temperature,sintering time,calcium oxide ratio and aluminum powder ratio on the preparation of Al-Ti master alloy were investigated by sintering method.The results show that:When the sample preparation pressure is 18KN,sintering temperature is 1500℃,sintering time is 20min,calcium oxide ratio is 1.6,aluminum powder ratio is 1.6,the metallization rate is 45.61%,the sintering reaction is full,the reaction degree is high,can nucleate more Al₃Ti phase,metal phase aggregation is better,can form low melting point Ca Al₂O₄ slag phase.XRD,SEM-EDS and XPS analysis of the sintered products show that the metal phase and slag phase are distributed in the sintered products obtained by thermite reduction of Ti O₂,and the main phases are Al,Al₃Ti and Ca Al₂O₄,which lays a foundation for the subsequent separation of slag and gold.The distribution of metal phase and slag phase is changed by adding self-made sintering additives,which is conducive to the separation of slag and gold.The effects of sintering temperature,ratio of aluminum powder,ratio of self-made sintering additives,adding different aluminum particle size and ratio of aluminum particle on the preparation of Al-Ti master alloy were studied.The results showed that the metal recovery reached 89.14%,when the sintering temperature was 1490℃,the ratio of aluminum powder was 1.2,the ratio of self-made sintering additives was 10%,and the aluminum particle with the particle size of 0.1mm was added and the ratio was 0.6.By XRF,XRD,SEM-EDS and XPS analysis of the sintered products,it is shown that the phases of the sintered products are mainly Al,Al₃Ti,Ca Al₂O₄ and Ca Al₄O₇,and the metal phases are all aggregated into small particles,which can be separated by crushing,grinding and sieving.Al-Ti-B master alloys were prepared by adding B₂O₃ at different sintering temperatures.The results show that the sintering temperature of1485℃can achieve the best sintering effect.XRD,SEM-EDS and XPS analysis of the sintered products show that the phases of the sintered products are mainly Al,Al₃Ti,Ca Al₂O₄,Ca Al₄O₇ and Ti B₂.Boron mainly exists in the aluminum matrix in the form of small particles of Ti B₂.The metal phases are aggregated into small particles.The slag gold can be separated to obtain metal.