| The magnetic pulse powder compaction technology belongs to a high-energy-rate powder compaction technology,which has the advantages of large compaction force,wide application range,high production efficiency,high safety and reliability,green pollution-free and easy to realize automated production.At the same time,it can provide an advanced and effective way for the compaction of difficult-to-form material powders and the preparation of complex parts,and has broad application prospects.In this paper,a preliminary exploration of the magnetic pulse powder compaction process was carried out.The performance of the compact was studied from the aspects of relative density,microstructure,microhardness and tensile properties.The compaction behavior of the powder during the compaction process was analyzed by numerical simulation.The green compact was sintered in vacuum.The influence of sintering temperature and discharge parameters on the properties of the sintered body was investigated.First,the mechanical properties and microstructure of copper powder compacts prepared under different discharge energies were studied.The influence of discharge energy on the relative density,microstructure of the end face,metallographic structure of the cross section,microhardness and tensile properties of compacts were analyzed.The function model of relative density and energy density was established.The results showed that when the discharge energy was 20 k J,the relative density of the compact reached 0.968.It was found that increasing the discharge energy could achieve the effect of refining the powder particles and improve the uniformity of the density distribution of the compact.The microscopic morphology of the tensile fracture showed that the failure location was at the junction of the copper powder particles,indicating that the powder particles in the compact were only mechanically bonded together under the action of the magnetic pulse pressing force.Then the velocity-time curve of the punch during the powder compaction process was obtained by DIC technology.The magnetic pulse powder compaction numerical model was established in the MSC.MARC finite element software.The changes of the relative density,equivalent stress and temperature of the green powder during the magnetic pulse pressing process were mainly analyzed.The results showed that the relative density and equivalent stress of the green compact showed a clear gradient distribution along the mold wall,while the relative density and equivalent stress distribution in the central area of the green compact were relatively uniform.With the increase of the discharge energy,the relative density distribution in the center of the green compact was more uniform,and the effect of friction on the relative density distribution at the edge of the green compact was more obvious.At the same time,it was found that the temperature rise was mainly concentrated in the area where the green compact was in contact with the mold wall,and the temperature change at the central area and the edge of the lower end surface of the green compact was small.Finally,the green compact was sintered by vacuum sintering process.The effects of sintering temperature and discharge energy on the relative density,micro hardness and tensile properties of the sintered body were analyzed.The results showed that the optimal sintering temperature of the copper powder compact was 800 ℃.It was found that sintering was able to increase the density of the compact and effectively reduce the residual stress generated by the work hardening during the pressing process.When the discharge energy wad 20 k J and the sintering temperature was 800 ℃,the comprehensive performance of the sintered body was the best,and the relative density was 0.981,microhardness was 72.4 HV0.5,tensile strength was 224.7 MPa and the energy absorbed by fracture was 6.81 J. |
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