Powder Metallurgy Method Of Titanium And Titanium Alloy

Titanium and titanium alloys are widely used in aerospace, chemical industry, automobile, bio-engineering, marine engineering, construction and other areas due to its low-density, high specific strength, good biocompatibility, and excellent strength in high temperature, highly resistance to corrosion and other advantages. In recent years, given the low removal rates, high yield, low-cost, high performance, nearly net formation of titanium products by powder metallurgy methods become the focus of attention by the researchers at home and abroad.In this paper compactibility, dehydrogenation, sintering and mechanical processing of titanium and titanium alloy have been studied systematically in order to establish the theoretical and technological foundation for the excellent performance and low-cost titanium and titanium alloy with the TiH2powder as raw materials.The results of dehydrogenation of TiH2show that, TiH2the dehydrogenation process is an endothermic process with500℃and530℃direct to the double endothermic peaks respectively. TiH2→TiH→of Ti (H) are the dehydrogenation processes. The XRD patterns show that TiH2began to decompose at400℃and end at700℃, then the solid solution of hydrogen removing from lattice when the temperature higher was than700℃. The decomposition reaction turned to the most intense state when the endothermic peaks at the peak temperature. Microstructure analysis results show that white needle-like scatter above the part of the particle at600℃and disappear when the temperature was higher than700℃sintering. Since the sintering temperature is not as high as α-Ti to β-Ti transition temperature, the grain does not grow up.The shrinkage and relative density of the sintered samples about TiH2show that the sintering properties of TiH2would be impacted by the compaction pressure, dwell time, sintering temperature, holding time and heating rate. Shrinkage and relative density of the sintered samples changed dramatically when the pressure was lower than400MPa, but it hardly changed when the pressure exceeded400MPa; Shrinkage and relative density of the sintered samples did not change unless the dwell time lasted less than20minutes; When the sintering temperature was lower than1200℃the shrinkage and relative density of the sintered samples changed more dramatically, but it will barely change when the sintering temperature was higher than1200℃. Meanwhile, the sintered samples were nearly in full density; Shrinkage and relative density of the sintered samples changed greater when the holding time was less than4hours, on the contrary, it hardly changed when the holding time lasted more than4hours; The higher the heating rate the bigger changes occurred in the relative density, so the lower the heating rate it is more conducive to the densification of the sintered samples.The atmosphere sintering experiment results show that the content of carbon, hydrogen, oxygen, nitrogen have reached the ASTM standard under the vacuum conditions of Ti and Ti-6A1-4V and the mechanical properties are also higher than the ASTM standard, but the thick grain of the sintered samples will seriously affect its using performance. Atmosphere (the mixed gas of hydrogen and argon) sintering experiments show that the grain of Ti and Ti-6Al-4V was refined, the mechanical properties are also higher than the vacuum sintering. This is a promising approach for producing titanium and titanium alloys, so, the atmosphere sintering experiments become a basic theoretical research for the materials of superior performance.The extrusion and swaging processing results of Ti and Ti-6A1-4V show that the size of the pore became small and the number of the pore become less, at the same time, the grain is significantly thinner and its mechanical property become better. Both the σb and σ0.2of the pure Ti has reached more than600MPa and450MPa respectively. In the mean time, the σb and σ0.2of the Ti-6Al-4V became higher, it has reached more than1160MPa and1060MPa after extrusion processing.But the two materials have a high elastic moduli, both of them has reached more than100GPa; For the swaging processing, the σb and σ0.2reduced a little after swaging processing, but the elastic moduli reduced dramatically; Ti was close to full density and Poisson’s ratio was close to0.5after mechanical process.