Preparation Of W-10%Ti Alloys

Thin W-Ti films have many great significant properties such as thermomechanical stability, low electromigration and high corrosion resistance etc., which make these films convenient as interdiffusion barriers for metallic contacts of semiconductor devices. Naturally, the quality of the film depends on the microstructure of W-Ti alloy.In this study, the preparation of W-Ti alloy as sputtering target was explored. W-10wt%Ti alloys were fabricated by hot-pressing W-Ti mixed powders under vacuum condition. Then XRD, SEM, EDS, TEM were used to analyze the microstructure of the alloy, density and hardness were also tested in order to analyze the correlation between microstructure and properties. The milling process of W-Ti powder and the sintering process including temperature, pressure and annealing were studied systematically.The morphology of mixed powder was affected by milling methods. The mixed powder particles were greatly refined through high energy ball milling, and a mutual solid solution between W and Ti was achieved. This is not found for conventional ball milling. Using the WC balls as the milling media, layered structure of Ti particles was formed. In contrast, for the resin milling balls, original powder characteristics were matained.Powders obtained by different milling process were sintered at the same condition (1400oC, 30MPa, 1 h), and a great discrepancy was observed in W-Ti alloys. Alloys prepared by high energy ball milling powder show a uniform structure of fine grain size, and Ti-rich phase has a size of 2 m or less. In contrast, alloy sinstered by powders that prepared by general ball milling with WC balls comprised a structure with a strip-shaped Ti-rich phase about 40 m in length. And powders prepared by general ball milling with resin balls formed a structure consisting a pure Ti phase in the centre of the Ti-rich phase.W-Ti alloys were fabricated with powders that prepared by general ball milling with rein balls, and the alloys comprised W-rich phase, Ti-rich phase and pure Ti phase. As sintering temperature increases, there was an increase in solution between W and Ti, and a decrease ofα-Ti phase amount. When the temperature was up to 1400oC, a precipatitated phase can be found in the Ti-rich phase.It was also found that the microstructure and property of W-Ti alloy was greatly affected by sinstering temperature and pressure. The density of alloys was increased with the increasing of sintering temperature, but Vickers hardness was first increase then decrease, and reached its highest value 6.32GPa when the composite was sintered at 1300oC. With the increase of sintering pressure from 20 MPa to 30 MPa, there was a little increase in density, the solution and hardness of alloys was almost the same.Further solid solution between W and Ti could be enhanced when the alloy was annealed at 1300oC for 1 h, and variety of precipitated phase can be found in the Ti-rich phase. The alloy's hardness was up to 6.69GPa.