Study On The Process Of Preparing Mo-Ti Alloy Target By Powder Metallurgy

Molybdenum has many excellent physical and mechanical properties and good chemical stability.It has a wide range of applications and good prospects in many fields.However,there are some defects in molybdenum,such as low recrystallization temperature,low room temperature strength and high brittleness,which limit its application.Solution strengthening is the most effective way to improve the properties of molybdenum.Titanium is one of the most effective and commonly used alloying elements,which is soluble in molybdenum.When the solid solution is formed,the lattice constant will change and the comprehensive properties of molybdenum alloy will be improved.At present,the common production process of pure molybdenum target in the market includes cold isostatic pressing,hydrogen sintering,hot rolling and machining.However,due to the embrittlement of titanium after hydrogen absorption,it is easy to crack during rolling of Mo Ti alloy.Therefore,in this paper,Mo Ti alloy was prepared by hot pressing sintering in powder metallurgy.The effects of ball milling,sintering and Ti content on the microstructure and properties of Mo Ti alloy were investigated.It lays a foundation for the preparation of Mo Ti alloy target and the study of sputtering properties.The main work of this experiment is as follows:When the ball milling parameter is set as 150 rpm,the ball material ratio is 4:1,and the ball milling time is 20 h,the agglomerates or flakes produced by ball milling are the least.If the rotation speed is too fast or too slow,the material will be uneven.If the ball material ratio is not properly selected,the ball material contact will not be sufficient,and if the ball milling time is too long,the agglomerates will be increased.The titanium phase in Mo Ti alloy was transformed into ?-Ti at 1500-1600 ?and dissolved in mo.With the increase of sintering temperature,the density,hardness and bending strength of Mo Ti alloy increase gradually.When the sintering temperature increased from 1500 ? to 1600 ?,the density of the alloy increased from 97.4% to98.4%,the bending strength increased from 354.1MPa to 396.5MPa,and the Rockwell hardness increased from 31.26 HRC to 32.58 HRC.With the increase of sintering pressure,the grain growth of Mo Ti alloy is obvious,the number of pores is greatly reduced,the crystallinity is increased,and the density of material is greatly improved.When the pressure is increased from 20 MPa to40MPa,the density is increased from 94.5% to 98.4%.The most obvious change brought about by the great increase of density is the improvement of performance.The bending strength was increased from 290.3MPa to 396.5MPa,and the Rockwell hardness was increased from 30.43 HRC to 32.58 HRC.The holding time also has an important influence on the structure and properties of molybdenum alloy.The grains grow up gradually to fill the pores during the holding process.As the holding time changed from 10 min to 180 min,the relative density of the material increased from 96.6% to 98.4%,the hardness increased from 31.92 HRC to32.58 HRC,and the bending strength increased from 382.6MPa to396.5MPa.However,insufficient holding time will lead to poor crystallinity,greatly reduced grain size and greatly increased fine grains.At 1600 ?,molybdenum and titanium can form continuous solid solution.With the increase of Ti content,the grain size increases and the number of pores decreases.The fracture type of mo-50% Ti is transcrystalline fracture,while the alloy with low Ti content is intergranular fracture.XRD analysis shows that there is only molybdenum peak in the alloy,but no titanium peak.It shows that ?-Ti has been completely dissolved in Mo,and with the increase of Ti content,the peak moves to a low angle,indicating that the lattice constant increases.With the increase of titanium content,the density of Mo and Ti alloy increases gradually.The hardness and bending strength of Mo and Ti alloys increase gradually due to the effect of solution strengthening and the decrease of the number of cavities.When the ratio of Mo to Ti is1:1,the best sintering results in 99.5% density,679.63 MPa bending strength and45.47 HRC hardness.