Microstructural Refinement And Deformation Mechanism Of The Constrained Groove Pressed Pure Titanium By Electro Impulse

Pure titanium has been widely used in aerospace,biomedical and other military and civilian fields because of its low density,low elastic modulus,good corrosion resistance and excellent biocompatibility.However,the low strength of pure titanium limits its application to larger load bearing components.As a new type of severe plastic deformation process,the constrained groove pressing method has the advantages of practicality and simplicity.Especially,it can be used to process large-sized plates.At present,the constrained groove pressing method has been successfully used in pure aluminum,copper and other FCC structural metal,but for the HCP structure of pure titanium,the deformation at room temperature is difficult to limit the compression deformation process prone to fracture.As a kind of unconventional energy,electric pulse has been shown to improve the plasticity of materials.Up to now,the deformation mechanism of pure titanium added electrical impulse regulation hasn't been studied yet.Therefore,in this study,the influence of pulsed current on the microstructure and mechanical properties of pure titanium was investigated by introducing pulse current in the process of limiting molding deformation,which is of great significance to further improve the properties of pure titanium.In this paper,titanium TA1 was selected as the research object,and the constrained groove pressing process was used,through changing the angle between the mold,and molding pass,and the electric pulse treatment to improve the pure titanium mechanical properties.(TEM)and electron backscattering technique(EBSD)were used to investigate the microstructural refinement and deformation mechanism of pure titanium during electric pulse treatment.The results show that the strength of pure titanium increases with the increase of molding pass after deformation.The microstructures of the pure titanium are obviously refined after the deformation.There are a lot of lamellar structure composed of twins and deformation bands in the grains,and the microstructures become thinner with the increase of the molding passes.The tensile strength of pure titanium can be improved by changing the molding direction.The microstructural refinement of the strip after cross-molding is more obvious and the dislocation entanglement increases,but the elongation decreases.The results show that with the increase of electrical pulse frequency,the strength of pure titanium is slightly increased and then decreased gradually.Under the pulse strength of 3kA pulse treatment,the tensile strength of the pure titanium is reduced gradually with the increase of electrical pulse frequency.Under the electrical pulse of 2kA and 10Hz after cross-molded two-pass process,the strength is up to 550MPa,which is 38%higher than that of the pure titanium.After the deformation,the elongation can be improved obviously by using the electric pulse treatment.This is because the movement of the dislocation can be promoted under the action of the electronic wind,and the deformation zone begins to annihilate,and then the pure titanium reacts and the degree of recovery increases with the increase of the electric pulse frequency.On the other hand,in the process of compression molding deformation,the twin synergistic dislocation slip,the which are {11-22}<11-2-3>and{10-12}<10-1-1>twin.The EBSD analysis show that the number of twins in the deformed pure titanium increases slightly,under the electric pulse treatment of 2kA and 10Hz.With the increase of electrical pulse intensity,the effect of electrical impulse on the deformation zone is more pronounced with 3kA pulse treatment,and the disruption of dislocation movement is reduced,and the strength of pure titanium is decreased and plasticity is obviously improved.