| Titanium alloys，as essential structural materials in the field of aerospace，havebeen widely applied to the blades, bearing, gear, shell and other structural components.Requirements of the titanium alloy properties, such as strength, toughness, resistance tohigh temperature and resistance to corrosion, has become higher and higher with thedevelopment of aerospace undertaking in recent years, and the research of high-strengthtitanium alloys is also gradually in-depth all over the world. In this paper I adopt theSelf-developed Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy，and systematically researchthe high temperature deformation parameters effecting on high temperature deformationbehavior of Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy as cast and the influence of thesolution and aging treatment parameters on the microstructures and the mechanicalproperties of Ti-6Al-4.5Mo-3V-3Cr-2Sn alloy of forging state.Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy as cast is compressed in differenttemperature and strain rates on the Gleeble–1500D hot compression simulationexperiment machine, Experiments show that when temperature is constant, flow stressof Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy as cast increases with the increase of strainrates; When strain rate is constant, flow stress of Ti-6Al-4.5Mo-3V-3Cr-2Sn titaniumalloy as cast decreases with the increase of deformation temperature; When thedeformation temperature range is800℃to800℃and strain rates is0.01s-1-10s-1,Thermal activation energy of the Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy as cast is554.22KJ/mol. The best high temperature deformation parameter ofTi-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy as cast is that the temperature is900℃,thestrain rate is0.01s-1.Experiments show that (+β)/β phase transition point of Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy is905℃. Using different solution temperature and coolingspeed on forging state Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy and analysising of thechange of microstructure and the mechanical properties.，the results show that when thesolution heat treatment temperature is in two-phase area,the microstructure of the alloyis composed of alpha and beta phase; when the solution heat treatment temperature isabove (+β)/β phase transition point, the microstructure of the alloy contains only betaphase; the strength of the alloy reduces with the increase of solution temperature,cooling in air alloy plasticity decreases first and when above850℃rises again,cooling by water alloy plasticity rises first and when the temperature is above(+β)/βphase transition point the plasticity decreases; and compared with cooling by water, cooling in air forging state Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy has goodcomprehensive mechanical properties with greater strength and higher plasticity.Using different solid solution temperature, aging temperature, aging time of heatpreservation for aging treatment of State of forging Ti-6Al-4.5Mo-3V-3Cr-2Sn titaniumalloy, the experimental results show that when the aging temperature and holding timeremain unchanged, the solution temperature in800℃to850℃, the microstructure ofthe alloy is composed of beta phase, the primary isometric alpha phase and thesecondary laminar alpha phase. With the increase of solution temperature in themicrostructure of the alloy the primary isometric alpha phase gradually decrease, thesecondary laminar alpha phase gradually increased, when the solution temperature reach895℃the microstructure of the alloy is entirely composed of mutual crisscrosslaminar alpha phase. With the increase of solution temperature, after aging treatment thestrength significantly increases, the plasticity sharply lower, so in order to improve thealloy strength and keep a certain plasticity, solution temperature should be around850℃. When solution temperature remains constant, with the increase of agingtemperature and aging time in the microstructure of the alloy the primary isometricalpha phase gradually decrease, the secondary laminar alpha phase gradually increased,and the strength and hardness reduces with the increase of aging temperature and agingtime, the plasticity increases to some extent. After850℃/1h/AC+560℃/8h/AC solutionand aging treatment forging Ti-6Al-4.5Mo-3V-3Cr-2Sn titanium alloy has the bestcomprehensive mechanical properties that the plasticity and strength get the best match: the tensilestrength is1520MPa, the yield strength is1469MPa, the elongation is8.54%, the fracture reductionis16.73%. |
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