The Study On Fabrication Process Of Titanium Alloy Hollow Spheres

Hollow Sphere composite is a kind of excellent vibration and noise reduction material which possesses a good performance.With the change of the size and wall thickness of the hollow sphere,the matrix and sphere materials,the performance of the hollow sphere composite can be changed widely,which is prevalent over the solid material.In addition,it's performance data can be applied not only to evaluation of specific applications,but also to establish a database to help computer-aided modeling of porous materials or components containing such materials.However,due to the poor interfacial bonding between the non-metallic hollow spheres and the metal matrix material,and the preparation of small-sized hollow metal spheres is difficult.Therefore the application of the metal-based hollow spheres composite is limited.According to the theory of constant pressure forging and the technology of diffusion bonding,the preparation and mechanical properties of hollow spheres under different plastic deformation distribution schemes were studied in two forming steps of stamping and forming / diffusion welding of titanium alloy.The results show that:During the process of preparing hollow titanium alloy hemisphere by stamping,the tensile strength of TC4 can reach 1212 MPa due to the phase composition of TC4 in delivery state being the dual phase structure of ?-Ti and ?-Ti.However,due to the inhomogeneous distribution of micro-structure,resulting in the capacity of plastic deformation is not enough,unable to achieve small diameter hollow hemisphere stamping process.Although the hexagonal close-packed structure limits dislocation slip,the formation of a large amount of deformation twins still provides sufficient plastic deformation capacity for TA4 sheet.Due to the large difference in stress state among the parts during the process of punchinging,and the punching rate obviously affects the material fracture failure.The reduction of the stamping rate can provide time to balance the inhomogeneous distribution of the deformation of the punchinging.During the reduction of the stamping rate from 30mm/min to 0.3mm/min,the aging failure position of the TA4 sheet moves from the position close to the edge of the stamp to the punch symmetry axis was 45 ° angle position.The ultimate deformation of the plate under the experimental design conditions gradually increased,finally experimental design stamping deformation achieved at 0.3mm/min.In the process of diffusion welding of titanium alloy sheet,in order to realize the thermoplastic deformation process of titanium alloy in the process of diffusion welding at the same time,the diffusion welding insulation temperature is designed to be 750 ?.Under the conditions of diffusion welding pressure of 15 MPa,the effect of holding time on element diffusion distance at weld location was studied.With the diffusion time is 2h,to study the effect of diffusion bonding pressure on the weld interface defects morphology.The results show that,with the diffusion time increasing,the element diffusion distance at the interface increases.The number and size of welding defects are reduced with diffusion welding pressure increases.Under the condition of 15 MPa pressure and 750? for 2h,a good diffusion welding joint was obtained between TA4 and TA4 plates,and no obvious plastic deformation occurred in the thickness direction of the welded plate.The optimal experimental parameters to achieve best hollow spherical Sphere in the stamping-diffusion welding process is 15 MPa,750 ?,for 2h.The axial cross section of the diffusion welded titanium alloy hollow Sphere is closer to the perfect circle,but the influence of the connecting plate thickness between the hemispheres is obvious.The deformation fillet appeared in the stamping process can not be eliminated,resulting in a large difference in the directionality of the mechanical properties of titanium alloy hollow Spheres.The optimal experimental processes to obtain a good roundness titanium alloy hollow Sphere in low deformation deformation stamping(punch stamping displacement of about 1.2mm)diffusion welding test is 25 MPa,temperature 750 ?,holding time 2h.Compared with the hollow Sphere material prepared by over-deformation stamping-diffusion welding process,the roundness of titanium alloy hollow spheres prepared by low deformation stamping-diffusion welding is superior.In the process of diffusion welding,the hollow Sphere connection plate has obvious plastic deformation,the larger plastic deformation balances the lack of deformation deformation of the stamping deformation.Meanwhile it's effectively eliminates the unobvious deformation rounding.There is no macroscopic welding defect in the wall thickness direction of the Sphere,and the unfavorable effect of the weld on the overall mechanical properties of the hollow Sphere is improved.