Anisotropic Mechanical Behavior And Plastic Deformation Mechanism Of Rolled Commercially Pure Titanium

Titanium alloy has excellent performance of light quality,high strength,corrosion resistance,high temperature resistance,etc,and has been widely used in the fields of aerospace and national defense.However,titanium alloy is a typical hexagonal closepacked metal,and the mechanical properties have significant opposite sex characteristics,which seriously restricts the development of its plastic processing technology.Therefore,the various heterosexual mechanics behavior and plastic deformation mechanism of titanium alloy are basic scientific issues that need to be broken in high performance materials.This article takes rolled commercially pure titanium as the research object.It comprehensively uses the use of macro-mechanical performance tests,micro-tissue structure representation,and crystal plastic simulation.The system has studied rolled commercially pure titanium in monotonous loading,plane strain compression,and low-cycle fatigue.The main work and research results are as follows:(1)With the help of the IBTC-5000 in-situ mechanical test system,combined with DIC technology based on the IX-CAMERAS high-speed camera,a small-sized "dumbbell-shaped" slice sample stretch mechanical behavior test platform was established.With the help of the platform and INSTRON8802 fatigue test system,the monotonous stretching and compression test of rolled commercially pure titanium along rolling direction(RD),transverse direction(TD)and thickness direction(ND)were carried out.Metallographic tests under 5% and 10% strain were carried out.The results show that: the asymmetry of the RD direction is the most significant,and the TD direction is the weakest;in the compressed stress strain curve,the ND and TD directions are the same as the same sex,but it has obvious compression with the RD direction.The opposite sex;in the stretch stress strain curve,the direction of ND,TD,and RD has obvious stretching of each direction;in the gold phase test results under5%and 10%strain,the twins when the RD direction compression is observed the largest quantity,the amount of twin in the direction of RD is the least.(2)Relying on the use of Visco-Plastic Self-Consistent Model(VPSC)model,the simulation has obtained the stress strain curve,hardening rate,slip/ twinning system of rolled commercially pure titanium along ND,RD,and TD.The law of the transformation of the twin volume fraction and texture evolution,through comparison with the test results,verify the rationality of the simulation result.The research results show that during the deformation process,the column surface slid occupied the dominant position.When the RD direction was compressed,due to {101?2} twinning in large number,the stress strain curve showed "S" types;as the deserved value increases,the relative activity of each sliding system and the twin system varies,Leads to anisotropy of the rolled commercially pure titanium;with the increase of the value of the value,the relative activity of the twin system changes.As a result,there are differences in the twin volume fraction,and the inhibitory effect of slip is more obvious,resulting in obvious tensile-compression asymmetry in the post-deformation period.(3)Self-made plane strain compression molds.With the help of the INSTRON8802 test system,plane strain compression testing platform was established,and the plane strain compression tests of rolled commercially pure titanium along ND,RD and TD were carried out.Metallographic tests under 5% and 10% strain were carried out.The results show that: the plane strain compression results in the direction of ND and TD have obvious anisotropy,while the plane strain compression results of the RD direction are not obvious.In the results of the gold phase test,the twin volume in the RD direction was the most.With the help of VPSC model,the stress-strain curve,hardening rate,relative opening rate of each slip/twin system,twin volume fraction and texture evolution of rolled commercially pure titanium under six planar strain compression deformations were simulated.Research shows that when the RD direction compressing ND direction constraint and RD direction compress the TD direction constraint,due to the {101?2};By analyzing the relative activity and twin volume fraction of each slip/twinning system during the analysis of the deformation process,it reveals the slip/twinning mechanism of various heterosexual behaviors during plane strain compression.(4)With the help of the INSTRON8802 test system,the rolled commercially pure titanium was carried out in low cycle fatigue test,which obtained hysteresis loops of RD and TD.By softening and hardening behavior and lagging lines,the alien mechanics behavior under low fatigue test was analyzed.The results show that the life of the low cycle fatigue test is significantly reduced with the increase of the strain amplitude;at the same strain value,the total number of low-week fatigue test samples under the RD direction is far greater than that of the TD direction;at the value,the three-level cycle softening characteristics are shown.As the value of the strain increases,at the first stage of the 1%and 1.5%strain amplitude values;at 1%,the lagging line moves towards the high stress direction.When the value of the strain in the direction of the RD is 1.5%,the lag line moves towards the small stress direction.The TD direction is the opposite.Research results can provide reference for optimizing plastic processing technology and research and development of high-performance titanium alloy materials.The thesis includes 48 figures,5 tables,and 90 references.