Study On Rolling And Microstructure Properties Of High Precision Ultra-thin Titanium Strip

The demand for high-precision metal ultra-thin strip is increasing day by day.In order to explore the evolution law of its mechanical properties and microstructure during rolling,this thesis mainly prepares ultra-thin titanium strip by mechanical rolling method.The mechanical properties and microstructure of ultra-thin titanium strip are characterized and analyzed by means of numerical simulation,nanoindentation,metal stretching,X-ray diffraction,scanning electron microscope and electron backscatter diffraction,etc.,which provides theoretical basis for the preparation of metal ultra-thin strip.The results of the research show that:(1)The finite element method is used to simulate the rolling of ultra-thin titanium strip,and the equivalent strain of shear stress is calculated according to elastic-plastic theory.It is found that the equivalent strain gradually increase with the increase of accumulated deformation,the equivalent strain will increase from 0.582 of 20% cumulative deformation to 7.514 of 80%cumulative deformation.Appropriate lubrication conditions and roll crown in the rolling process can obviously reduce the roughness,improve the surface quality and tolerance accuracy of ultra-thin titanium strip;(2)During rolling deformation,slip is the main plastic deformation mechanism of asynchronous rolling,the {1(?)00}<11(?)0> cylinder slip is easy to stare.However,the plastic deformation mechanism of synchronous rolling changes from twinning to slipping,and the main twin types are {11(?)2}<(?)(?)23>(compression twin)and{10(?)2}<10(?)1>(tension twin);(3)The phase transition from HCP-Ti to FCC-Ti occur in the rolling process of ultra-thin titanium strip,and the phase content of FCC-Ti increase with the increase of deformation,from0.56% under 20% deformation to 5.23% under 80% deformation.Under macroscopic and microscopic texture observation,with the increase of deformation,the main texture types of ultra-thin titanium strip is {0001} plane parallel to ND direction,<101 0> parallel to DD direction cylinder texture;(4)After annealing at 650℃/1h,the tensile properties of the ultra-thin titanium strip will show size effect: with the thickness decreasing,the tensile strength and elongation both show the characteristics of weaker,and the specimen section will show few/single layer equiaxed crystals.After rolling,the hardness of the ultra-thin titanium strip is significantly improved,and the load required for reaching the depth of 1000 nm of the ultra-thin titanium strip under 80% deformation is increased by 57 m N compared with the un-rolled strip.Fracture behavior of ultra-thin titanium strip will change from plastic fracture to cleavage fracture;...