| The aerospace industry is an important national strategic industry,and it is also a significant symbol of national defense capability,economic potentiality and industrial level in China.In company with the increasingly serious global energy crisis,environmental pollution and national security issues,the lightweight design of aircraft structures is an important development tendency of aerospace industry in the future.Titanium alloy has lighter weight,better performance,and can also serve in high temperature,high pressure and corrosive environment for a long time,which is incomparable with other conventional metallic materials.At present,the use of titanium alloy materials in aviation aircraft has become an important indicator of its technological advancement.TC21 titanium alloy is a new titanium alloy material developed by China,which has excellent performance of long-term service in high temperature,high pressure and corrosive environment.TC21 titanium alloy material is widely used in aircraft wings,fuselage,landing gear and engine joints and other key parts.Forging is the most widely used plastic forming process of titanium alloy materials.This process not only achieves the size and shape of titanium alloy structural parts,but also precisely regulates the microstructure and properties of the alloy.However,the traditional titanium alloy die forgings for aviation have the problems of small size,heavy weight,low productivity and low reliability of connection between small forgings.At present,the titanium alloy structural parts for aviation are gradually changing towards integration and large-scale.For purpose of finding the specific process parameters and practical experience of manufacturing and production of large aviation forgings such as TC21 titanium alloy,it is essential to study the forging forming process of large aviation titanium alloy forgings.In this paper,the forging and forming characteristics of TC21 titanium alloy material were studied and analyzed with the background of the large forgings of an aircraft in China.Firstly,the high temperature rheological properties of TC21 titanium alloy material under different deformation temperature and strain rate conditions were obtained with the aid of Gleeble-3800 thermal simulation testing machine.And the data of high temperature rheological property curves which were obtained from the test were analyzed and studied.Then,numerical simulation analysis technology was used to simulate and analyze the small cylinder hot upsetting test of TC21 titanium alloy under different forming process parameters and the die forging of quasi ? forging process of the material.Finally,combined with the high temperature rheological properties of TC21 titanium alloy material and the results of numerical simulation analysis,the corresponding practical experiment was established to verify it.Then the physical and chemical tests and analysis of the forgings obtained from the experiment were carried out.The results of this subject provide instructive meanings for the research and actual production of TC21 titanium alloy large aviation forgings.The main research contents of this paper are shown below:(1)Based on the theory of plastic deformation of titanium alloy,the hightemperature rheological properties of TC21 titanium alloy in the process of thermoplastic deformation were obtained by high-temperature hot compression testing machine.According to the high-temperature rheological curves under different conditions,the effects of deformation temperature and strain rate on the thermoplastic deformation of materials were analyzed.(2)Based on the isothermal thermal compression test,the small cylinder hot upsetting test of TC21 titanium alloy was simulated with the aid of DEFOEM-3D FEM simulation analysis.The distribution of equal stress,equal strain and load of TC21 titanium alloy during hot compression under different process parameters(friction factor,strain rate,deformation temperature and deformation degree)were gotten by tests.(3)The forging process of TC21 titanium alloy at quasi ? forging temperature was analyzed by using DEFOEM-3D based on the results of isothermal thermal compression test and small cylindrical hot upsetting simulation test.The effects of strain rate and friction factor on the properties of forgings in different deformation regions of the same forging were studied.(4)The results of the material isothermal thermal compression test and numerical simulation analysis were combined to perform practical test verification of TC21 titanium alloy material.Firstly,we designed a reasonable mold and manufactured it according to the research requirements and the characteristics of the material.Next,the effect of cooling condition on microstructure and properties of TC21 titanium alloy forgings with different thickness was analyzed and the reasonable cooling method was determined.Then TC21 titanium alloy bars were selected for free forging and die forging trial production,and TC21 titanium alloy final forgings with different deformation degree were obtained.At the end of the experiment,the physical and chemical analysis of each deformation area of the forging was carried out,and the microstructure and mechanical properties of different deformation areas of the forging were analyzed.Finally,we obtained the law of the influence of the deformation of TC21 titanium alloy material on the microstructure and properties of forgings under quasi ?forging process,and proposed the process design criterion for large aviation forgings of TC21 titanium alloy. |
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