Preparation Of Ti-6Al-4V Alloy Powder By Vacuum Aluminothermic Reduction Of Sodium Fluorotitanate

Ti-6Al-4V alloy with good hardness,light weight,corrosion resistance and good plasticity characteristics,widely used in aviation,marine and other industries.At present,Ti-6Al-4V which accounts for more than 50%of the total amount of titanium is the most widely used titanium alloy of titanium industry.Ti-6Al-4V alloy is considered to be"grass-roots" of the titanium industry.The alloy is mainly composed of ?+? phase that can be heat treated to achieve moderate strength.In this paper,the preparation process of Ti-6A1-4V powder using Al powder as reducing agent,Na₂TiF₆ and V or Al-V powder as raw materials,were studied.The process of separating titanium from titanium-containing cryolite obtained in the first aluminothemic reduction process by two-stage aluminothermic reduction was studied.The main results are as follows:The calculation of saturated vapor pressure of fluoride shows that all of the fluorides can be separated from titanium alloy by vacuum distillation at temperature above 1100?.The aluminothemic reduction reaction occurred at 660? during the preparation of Ti-6Al-4V alloy powder with aluminum powder as reducing agent and vanadium as additive.With the increase of reduction temperature,the recovery rate of the alloy increases,and the mass fraction of aluminum in the alloy decreases,and the mass fraction of titanium increases,and the mass fraction of titanium in the by-product titanium-containing cryolite generally increases.With the increase of reductiontime,the recovery rate of the alloy increases,and the mass fraction of aluminum in the alloy decreases,and the mass fraction of titanium increases,and the mass fraction of titanium in the by-product of titanium-containing cryolite increases.With the increase of the excess coefficient of aluminum powder,the yield of the alloy increases,and the mass fraction of aluminum in the alloy increases,and the mass fraction of titanium decreases,and the mass fraction of titanium in the by-product of titanium-containing cryolite decreases.The addition of NaF has a great influence on the content of titanium in the by-product When the addition of NaF is small,more amount of NaAlF4 is formed in the by-product When the stoichiometric coefficient of NaF is six,it mainly forms cryolite.For low melting point and high saturated vapor pressure of NaAlF4,it can easily lead to the loss of by-products.With the increase of the stoichiometric coefficient of NaF,the yield of the alloy increases,and the mass fraction of aluminum in the alloy increases,and the mass fraction of titanium decreases,and the mass fraction of titanium in the by-product of titanium-containing cryolite increases.The phase distribution of vanadium in the Ti-6Al-4V alloy prepared by V powder as additive is not uniformAt 1200?,the reduction time is 90 min,Al powder excess coefficient is 2%and the stoichiometric number of NaF is six,the content of aluminum and V in alloy products meeting the national standard can be obtained.In the process of preparing Ti-6Al-4V with Al and Al-V as reducing agent,the effect of reduction condition on reduction processis similar to that prepared with Al and V,but the phase distribution of vanadium in the prepared Ti-6Al-4V is relatively uniform.The experiment of two-stage aluminothermic reduction with titanium-containing cryolite shows that the AlTi alloy can be obtained by aluminothermic reduction at the conditions of reduction temperature 1050?,Al powder to titanium-containing cryolite mass ratio 1:1 and holding time 30 min.The amount of aluminum consumed is less and the content of titanium in cryolite is up to the national standard.