The Microstructure, Properties Of Some Titanium Alloys And Sputtering Process Of Targets

With the development of high-tech new material, the research and development of high quality titanium alloy target and special titanium alloy materials must rise to digital design level. Due to the traditional phase diagram thermodynamic method cannot calculate the site occupancy fractions of alloying elements in defferent sublattices correctly, in this thesis, the sublattice models were employed and aided by first-principles calculations to predict the site fractions and ordering behaviours of some titanium alloy intermetalllics. The elastic constants and modulus of Co3 Ti-based alloys with L12 type were calculated by building supercell based on its fine microstructure. The interactions between ions and solids in alloy targets were simulated based on the cascaded collision theory. Some pollution-free and uniform titanium ingots were prepared by vacuum induction levitation melting method. And the heat treatment procedure, equilibrium phase stucture and microstructure were predicted based on phase diagram calculation. Some considerably good quality alloy films were prepared by magnetron sputtering experiment using self-made high quality binary or ternary titanium alloy targets.The calculated results of the ordering behavior of the L12 type Co3Ti-based alloys show that the stoichiometric intermetallic Co3Ti is fully ordered intermetallics, meanwhile, the site preferences of alloying elements are independent of the heat treatment temperature. The systematic and quantitative studies on the ordering behaviours of Co3Ti based alloys adding with a small amount of the third transitional metal element M were also carried out. When M represents Fe or V atom, M occupies 3c sublattices, and when M represents Al atom, it occupies both la and 3c sublattices. The site occupation distribution rules of alloy elements are relatively complicated. With the increase of extranuclear electrons, the site preference of the transition metal tends to change from 1a sublattices to 3c sublattices gradually. The site occupancy fractions varying with temperature were also calculated in Co2Ti (C36), CuTi2 (C11b), γ-CuTi (B11) and NiTi2 alloys.The calculated results of elastic properties of L12_Co3TiM (M=Al, Fe and V) intermetallics show that the elastic constants meet the stability condition of crystal structure. Co3TiM alloys show some brittleness according to the tough/brittle criterion. Al, Fe or V atoms occupy 3c (Co) sublattices in stable structure, but the elastic modulus tend to smaller than supposing they occupy la (Ti) sublattices. It reveals that the stabilities of the structure of alloys are enhanced by adding alloying elements, and alloying elements tend to occupy the sites where they could improve alloy’s ductility.The ion-beam sputtering process simulation results of alloy target by using SRIM software package show when fixing incident ion for Argon, incident energy at 10 keV, and varying incident angle, the maximum sputtering yield is obtained when incident angle is at 75°. There is a considerable deviation of the ratio of YTi/YM between the sputtering atoms and targets when the target compositions show a large difference in elements’surface binding energy during the sputtering process. The correlation plots of composition ratio between the sputtering atoms and targets were figured out by simulating a series of alloy targets. The plot of composition ratio is linear tendency. Thus the compositions of alloy target material and film can be designed accordingly.After homogenization heat treatment Co3Ti ingot, most of β-Co2Ti phase (HCP structure) disappeared in casting-state structure, and almost single y’-Co3Ti phase (FCC structure) was obtained. Alloy’s hardness was reduced from 615.5HV (as-cast) to about 220±5 HV (heat treatment). It shows that the alloy machinability can be improved by adopting proper heat treatment process. When homogenization heat treatment is at 800 ℃ for 5 hours, Ti4Cu alloy’s microstructure was more uniform and its hardness increased, while Ti51.5Cu29Nii18.5 alloy has no obvious changes.The sputtering process conditions were tested by using magnetron sputtering equipment based on self-made titanium alloy targets. The results show that the compositions of alloy films agree well with that of Ti50Ni50 and NisoCrso alloy targets. However, there is a selective sputtering between Ni and Mn atoms (element Ni preferentially) in Ni70Mn30 alloy from simulation, which considerably disagree with current experimental results. Further exploration is nessary to identify the composition deviation among the target, sputtering yields and films by combing sputtering with deposition process simultaneously.