Kinematics Laws of ACDR Processing of Titanium Disc and Its Effect on Microstructures and Properties

Author:Zheng Yong

Supervisor:liu dong


Degree Year:2018





Recent years,as one of the key components of high performance aerospace engine,due to the continuous development and competition of industrial technology,such parts gradually develop towards the overall design during the research and design process and towards the near net shape forming during production and manufacture process.However,the existing research and application of large size forging equipment is difficult to match the development and demand of rotary disc.And the application of high efficiency low loading forming of ACDR(abbreviated by axial closed die rolling)technology can properly solve the above problems.Therefore,it has an important theoretical and practical significance on deeply studying this technology.Since the lacking of papers about kinematics and microstructure properties of thermal deformation for less deformable metal in rotary forging process,titanium alloy disc plastic deformed by ACDR is regarded as subject investigated,combined with the FEM analysis and experimental verification,while the metal plastic flow behavior,the best process parameters,the evolution of thermal mechanical parameters and controllability of microstructure properties are treated as research objective,the compression behavior,torsion behavior,thermal parameter distribution and evolution of microstructure and properties were systematically studied,main research contents and results are reflected as follow:Utilizing the accurate finite element analysis model of ACDR forming process,the evolution rule of local plastic deformation zone is clearly defined.①Contact region:With the increasing of axial compression rate η,axial compression speed v and speed radio v/ω,with the decreasing of rotation rate of lower die ①,inclination angle of upper die y,the angle of contact region,contact arc,bite arc and separate arc are gradually increasing.②Axial section of contact region:With the increasing of ωand y,the decreasing of v and v/ω,instantaneous radius and max instantaneous radius are gradually increasing.With the increasing of η、v、ω and v/ω,the decreasing of y,min instantaneous radius is increasing.With the increasing of η、v and v/ω,the decreasing of γ and ω,the height of max instantaneous radius is decreasing.③3D flow line torsion behavior:Radial tensile degree obtains a significant effect on strain increment.Based on the accurate calculation of instantaneous radius of contact area,the contact area coefficient λ is corrected as follow:λ=0.45(?)The average error is less than 3.7%.The motion law of arbitrary particles in the deformation zone is analyzed,Archimedes spiral traj ectory equation is built as follow:Rηu=R0+a1+b1η/c1+d1ηθThe average error is less than 4.2%.The optimal process objective function is established as follow:Dop=Dlti+Dlpf+Dtu Load and torque growth range could be represented by Dlti,plastic flow degree could be represented by Dlpf,the uniformity of thermal mechanical parameters could be represented by Dtu.Main schemes and optimization are designed through RSM.Based on this model,the optimal process parameters are obtained as follow:v/ω=6/1,γ=6°.Comparison analysis of the plastic deformation zone and conventional forging mechanism of ACDR is carried out.Then the evolution law of thermal mechanical parameters could be defined as follow:Strain incremental in ACDR process is greater than conventional forge.Also the temperature uniformity is higher.Max strain during ACDR process could reach to 1.75(conventional forge is 1.25),Max temperature difference is 42 C(conventional forge is 100 C).The microstructure evolution and hardness distribution of titanium alloy discs deformed by ACDR are found as follow:The content and equivalent diameter of primary a,thickness of lamellar a found during ACDR process is less than conventional forge,and grain refinement is obvious.Additional torsion,periodic and gradient thermal mechanical parameters have a close relationship with the distribution of microstructure and property,grain refinement of each regional organization is different.Microstructure in each region of complex discs deformed by ACDR process is more uniform,and grain refinement is significant,the content of primary a is 33%,the size of primary α is 2.75μm,average grain refinement degree is 90.83%.The nano crystal could be observed in the corner area of upper surface,min grain size is 50nm,the corresponding strain is 7.5,average grain refinement degree could be reached 99.83%.Therefore,ACDR obtains the characteristics of high efficient and continuous grain refinement.On account of ACDR’s kinematics and microstructure control methods,in view of the high loading and complex blanking technology used in the past,the low-load and high-efficiency ACDR plastic deformation process of TC11 thin-walled parts,ultra-high strength steel bowl-shaped parts and alloy steel wheel have been developed,single fire forming,high efficiency and low cost could be achieved by all the above processes.