Basic Research On Preparation Of Ti6Al4V Alloy Powder By Multistage Depth Reduction Process

Ti-6Al-4V(TC4)alloy is one of the earliest and most widely used titanium alloys.Its output accounts for 50%of the total titanium alloy output,and accounts for 95%of all titanium alloy processed parts.It is a typical ?+? type titanium alloy.The ? phase at room temperature is about 15%and the rest is a phase.It has good strength,toughness,plasticity,formability,heat resistance,candle resistance and biocompatibility.Used in aerospace,biomedical and other high-end industries.Current methods for producing TC4 alloys include atomization,rotating electrode,ball milling and electrolysis.The atomization method uses gas to blow the molten TC4 alloy into spherical particles,and then rapidly condenses to achieve the purpose of atomization;the rotating electrode method welds the TC4 alloy material into an electrode,then rotates at a high speed,and changes the molten TC4 alloy by centrifugal force.The droplets are rapidly condensed to achieve the purpose of powdering;the ball milling method uses raw powders to achieve long-term ball milling in the high-energy ball mill to achieve the purpose of alloying;the electrolytic method uses electrodes made of the target product's oxide to rely on the cathode reduction reaction Alloy powder.The first three methods are currently the mainstream methods for producing TC4 powders.There are problems with high equipment maintenance costs,complicated processes,and high production costs.Electrolysis is still in the experimental stage.In view of the deficiencies in the current production of TC4 powder,the group proposed a new idea for the preparation of TC4 alloy powder by multi-level deep reduction method to solve the current difficulties and expand its application.The specific method is to mix TiO2,V2O5 and Al,and mix it with Mg powder for the first reduction in a self-propagating manner.The primary reduction product is pickled and then calcium is added for further reduction.The main research contents and conclusions are as follows:(1)Thermal analysis results show that the adiabatic temperature of the primary reduction reaction system is greater than 1800K,and the self-propagation reaction can proceed.For the complexes that may be generated in the reaction,such as MgTiO3,MgTi2O5,Mg2TiO4,MgV2O6,Mg2V207,MgA12O4,Al2TiO5,etc.It can be reduced by Ca during deep reduction.Low-order oxides such as TiO and Ti2O produced by primary reduction reactions can be reduced by Ca during deep reduction.(2)A primary reduction experiment showed that the primary composition of the primary reduction product is TiO and a small amount of Ti2O and Ti60.With the addition of reducing agent Mg,the Mg content in the acid-washed product increased from 4.49%to 7.22%.As the sample preparation pressure increases,the Ti,Al,V content in the product increases first and then decreases.The increase of the initial reaction pressure contributes to the reduction reaction.With the increase of the initial reaction pressure,the oxygen content in the product decreases from 27.73%to 17.84%.The best experimental conditions for obtaining a reduction experiment are as follows:the amount of Mg is 0.9 times that of the equivalent;the sample pressure is 10 MPa;the initial reaction pressure is 0.2 MPa.The oxygen contents of the obtained products Ti,Al,V,Mg,O after pickling were respectively 68.20%,7.00%,3.72%,3.24%,and 17.84%.(3)The experimental study of acid leaching process showed that the content of Ti2O and Ti60 in the product decreased with the increase of temperature,the time of acid leaching,the increase of the liquid-solid ratio and the increase of the concentration,and the removal rate of magnesium was increased.The optimum conditions for experimental acid leaching experiments were as follows:room temperature leaching,acid concentration 4 mol/L,leaching time 40 min,liquid to solid ratio 8:1,and two-stage leaching.At this point,the recovery rate of Ti was 87%,the recovery rate of V was 75%,and the removal rate of Mg was 97%.(4)The depth reduction experimental study showed that the oxygen content in the product decreased from 2.97%to 0.49%and then remained at about 0.6%as the amount of Ca increased.As the reduction time increases,the oxygen content in the oxygen content product in the product is reduced from 0.56%to 0.25%and then maintained at about 0.3%,With the increase of reduction temperature,the oxygen content in the product first decreased from 3.6%to 0.81%and then increased to 4.65%.The best conditions for determining the depth reduction were as follows:the amount of calcium was 0.75 times the mass of the precursor;the reduction time was 2.5 hours;and the reduction temperature was 900?.The final alloy composition is:Ti89.75%Al6.2%,V3.64%,O0.24%,Mg0.01%,Ca0.16%.