Research On High Temperature Deformation Behavior Of Ti60 Titanium Alloy Sheet And Non-isothermal Gas Pressure Forming Process

With the continuous development and progress of today's aero-engine technology,the amount of high-temperature titanium alloys is gradually increasing.Among them,Ti60 titanium alloy is a near-?-type titanium alloy independently developed by Chinese.This alloy can be used stably at 600°C for a long time.Because of the high strength and poor forming performance under normal temperature conditions,traditional titanium alloy forming uses isothermal forming processes under high temperature conditions,that is,the die and the metal to be formed are heated to a higher temperature at the same time and then formed,but heating the die causes a lot of energy waste.Therefore,the resistance heating and non-isothermal air pressure forming process is proposed to greatly reduce the temperature of the die.At the same time,the resistance heating of the sheet to be formed can effectively improve the forming efficiency and reduce the energy waste,and achieve high-precision forming of Ti60 titanium alloy sheet.Corresponding experimental research is carried out for the design of the forming process route of Ti60 titanium alloy involved in this process.First,the high temperature deformation behavior of Ti60 titanium alloy was studied.The high temperature deformation performance under the conditions of 850?,900?,950?,1000?and strain rates of 0.1s^-1,1s^-1 and 10 s^-1 was analyzed.Material properties change with temperature and strain rate.The results show that:the yield strength and peak stress of the material decrease with the increase of temperature,and the elongation increases with the increase of temperature;at a certain temperature,the yield strength and peak stress of the material increase with the increase of the strain rate,the elongation decreases with the increase of strain rate.Microstructure analysis and performance testing under different heat treatment conditions for Ti60 titanium alloy is finished,the results of analysis of the effect of solution aging scheme and cooling rate on the material structure and performance found that within a certain range,with the increase of solution temperature and the extension of the solution time,the tensile strength of the material at room temperature and 600°C increases,and the elongation will decrease;within a certain range,with the decrease of the aging temperature and the extension of the aging time,the tensile strength of the material at room temperature and 600°C increases,and the room temperature elongation decreases.The elongation at 600°C is improved.Carrying out heat treatment of Ti60titanium alloy with different cooling rates,the results found that the tensile strength of the material increases with the increase of the cooling rate.Under the condition of 980?,the cooling rate increases from 1?/s to 100?/s,and the material tensile strength Strength increased by about 200 MPa.Conduct research on contact heat transfer between Ti60 titanium alloy sheet and die,analyze the effect of temperature of the die and contact pressure between sheet and die on the cooling rate of sheet through finite element simulation,and design contact heat transfer experimental die and formulate corresponding experimental programs to change different temperature of the die and the contact pressure,the experiment shows that:under the condition of a certain contact pressure between the sheet and the die,with the increase of the temperature of the die,the cooling rate of the sheet shows a downward trend;under the condition of a certain temperature of the die,with the increase of the contact pressure between the sheet and the die,the cooling rate of the sheet is showing an upward trend.The resistance heating process and non-isothermal air pressure forming process of Ti60 titanium alloy sheet are simulated by finite element method.The current density is determined to be 12 A/mm² through the analysis of the heating time and the temperature field of the sheet;The bulging height increases with the increase of the bulging pressure;in the case of a certain bulging pressure,raising the temperature of the die can effectively increase the bulging height while improving the accuracy of fillet forming.Performing bulging experiments under different bulging pressures,pressurization rates and die temperature conditions,it is found that increasing the bulging pressure and pressurization rate within a certain range can effectively increase the bulging height of the sheet;increasing the temperature of the die can also effectively increase the bulge of the sheet Shape height,while improving the accuracy of sheet fillet forming.