Research On The Plastic Deformation Of TA15Titanium Alloy At High Temperature Using CPFEM

Crystal plasticity theory,which based on the combination of the physicalmechanism of crystal plastic deformation,deformation geometry,single crystal orpolycrystalline elastoplastic constitutive equations,explains the plastic deformationbehavior of materials on meso scale (i.e grain size). Crystal plasticity finite elementmethod (CPFEM) is a recently-developed method based on crystal plasticitytheory and finite element method.This method can reflect the microscopicproperties of the material from physical material deformation mechanisms moreaccurately.Crystal plasticity finite element simulation has become a hot point inmechanic and materials research.Titanium and titanium alloys are important structural materials,which arewidely employed in the aerospace and other fields. Titanium have two allotropiccrystalline form: hexagonal close-packed (HCP) lattice of α-Ti and the bodycentered cubic (BCC) lattice of β-Ti, the deformation mechanism of the two latticesdiffers.The finite element method,crystal plastic theory and cellular automaton wereused in this paper.Based on the different in the lattice structure of TA15alloy,thehigh-temperature plastic deformation was studied,hot deformation behavior ofTA15alloy at beyond and below the transformation point were also explored.The initial grain morphology of TA15alloy beyond the transformation pointwas obtained by using Cellular Automaton(CA).The crystal plastic finite elementmodel of plastic deformation of TA15beyond the transformation point wasestablished. The results shows that in the plastic deformation process, stressdistribution shows obvious differences between the grains and the graininterior,plastic deformation is very uneven inside and outside the grains. Byanalyzing the shear strain of the slip system, the acutuation of the slip system ingrains are discussed.Due to the difference of the orientation,the slip systemsactuate varied in the grains;the shear strain of the slip systems are not the samewithin a grain in order to coordinate the strain of the adjacent grain.The crystal plastic finite element model of plastic deformation of TA15belowthe transformation point was established to research the strain stress state and the orientation distribution of the grains of the HCP polycrystal after deformation.theresult shows that the constitutive model based on the deformation mechanism ofHCPcrystal can well describe the strain and stress state of the material.The study oforientation distribution of the representative element during deformation showsthat:the changes of the orientation in the same plane has a certain rule,not mutatedwithin deformation;the orientation distributions in different planes vary much.