Research On Preparation Of Oxygen Solid Solution Titanium Sintered Material With High Strength And High Ductility

Due to its high specific strength,high Young's modulus and excellent corrosion resistance,titanium alloys are widely used in space,chemical,medical and military applications.The strength of pure titanium is low,and titanium alloy can improve performance by adding precious metals,but the plasticity is lowered.In this paper,the method of spark plasma sintering is used to prepare oxygen solid solution strengthened titanium,and the mechanism of synergistic improvement of strength ductility is studied.The research content of this paper mainly includes two aspects: Firstly,the densification process of titanium during spark plasma sintering is discussed,and the influence of different process parameters on the microstructure of the sample is tested and compared.Then study the oxygen solid solution strengthening titanium,study the effect of titanium dioxide doping method,sintering temperature and oxygen content on the properties of solid solution strengthened titanium.For the ball milling method,the test found that the pure titanium powder treated by high-energy ball milling,with the prolongation of the ball milling time,the powder particle size first becomes smaller,and then the powder welding particles increase.No new phase appeared in the whole ball milling process,and the impurity element increased with the ball milling time,indicating that the amount of impurities brought by the ball milling was controllable.Compared to the unmilled powder,the ball milled powder has a higher energy and the densification temperature becomes lower.According to the sintering temperature,it is found that as the temperature increases,the sample density increases continuously,the hardness of the sample increases,and eventually stabilizes.The pure titanium phase transition temperature is 882?,and the atomic migration rate of ? titanium to ? titanium is faster.When it is sintered above this temperature,the densification efficiency is higher.The longer the holding time,the higher the density of the sample,but the density increase is slower.The length of the holding time mainly affects the degree of elemental diffusion and the morphology of the tissue.The heating rate has little effect on the density,and the heating rate essentially changes the holding time,the heating rate is too fast,and the particle bonding is insufficient,resulting in defects remaining in the matrix.With the increase of pressure,the degree of densification in the initial stage of sintering is getting higher and higher,but when the pressure is higher than 20 MPa,the influence of the pressure increase on the densification process at the initial stageof sintering is reduced,and the state of the particles is accumulated after the sintering pressure is higher than a certain value.The effect is not large,and the density of the sample in the middle and late stages of sintering increases with the increase of pressure.For the middle of sintering,as the temperature increases,the diffusion creep caused by the grain boundary diffusion or grain boundary slip Certain promotion.After obtaining the sintering densification law of titanium,the test began to study the titanium alloy of solid solution oxygen.It was found that the mechanical properties of the samples sintered by the ball milled mixed powder were much higher than those of the conventional mixed powder samples.For the oxygen doped titanium,the unballured sample has a lower hardness and is very uneven.The XRD data of the ball milled sample showed that the peak angle was shifted to a smaller angle than the non-ball milled sample,which indicated that the ball milled powder could be the ideal blending powder.For the unballured sample,the hardness increases with the increase of temperature,and the XRD peak increases with the temperature increase,indicating that the increase of temperature contributes to the decomposition of titanium dioxide and the solid solution of oxygen.In the sample pre-doped with oxygen at 1.5 at.% O,the phase transition temperature of titanium increased as the oxygen content increased,and the temperature required to obtain a denser structure was higher than that of the pure titanium sample.The sample sintered at 950? has poor plasticity due to the lower temperature of the component,the complete diffusion of oxygen,and the formation of uniform equiaxed grains.Although the sample at 1050? has the highest density,the grain grows significantly from the grain point of view,so the sample strength at1050? is lower than that at 1000?.The microstructure and properties of solid solution-strengthened titanium with different oxygen contents were studied.The sample was pre-doped with 1.0,1.5,2.0at.% O.The yield strength of the sample increased proportionally with the increase of oxygen content,and with the increase of oxygen content,XRD The peak shifts to a small angle,and the dissolved oxygen tends to remain in the octahedral position of the ?-Ti lattice.Since no other particles or precipitates appear and there is no fine grain strengthening,this indicates that the strengthening mechanism of titanium is solid solution.strengthen.