Effects Of Pulse Current On Deep Drawing Deformation And Diffusion Bonding Of Aluminum Matrix Composites

SiCp/Al composites have been utilized in lightweight structures in the field ofairplanes and aerospace etc. because of their many wonderful properties, such asthe high specific strength and modulus, good high temperature and wear resistance,lower thermal expansion coefficient, stable geometric accuracy and so on. However,SiC particle in Al alloy matrix make the plasticity and ductility of SiCp/Alcomposites decreased, which restrain the application of SiCp/Al composites inindustry. In order to solve issues of the secondary material working, the hith-intensity pulse current to get through SiCp/Al composites sheet were applied, whichcan produce Joule effect and electroplastic effect. The feasibility of pulse currentauxiliary deep drawing and process parameters were investigated in this work. Inaddition, the pulse current auxiliary TLP diffusion bonding of SiCp/2024Alcomposites sheet were studied by using mixed slurry of Al-Cu-Ti powder interlayer.Based on much complexity of electric-thermal properties during pulse currentgetting through metal sheet, pulse current heating were studied in this work,including pulse heating velocity, heating temperature, thermal conductivities,thermal convection etc. The results show that the stainless steel （SUS304） withlower thermal conductivities and higher electric resistance was attempted to reducethe thermal transmission between sheet and copper electrode, which promoted thetemperature distribution. In addition, the effects of pulse current heating on tensileproperties and microcrack healing were studied to provide the experimental andtheoreticl supports for application of pulse current auxiliary forming technology inindustry.Take account of electric-thermal properties synthetically during pulse currentgetting through SiCp/2024Al sheet, the feasibility of pulse current auxiliaryforming were analysed and the forming die were designed. Through the choice andoptimization of process parameters, the workpiece of SiCp/2024Al composites weredeep drawn successfully. The workpiece exhibit good shape retention, surfacequality, and high geometric accuracy. Fluoroscopy measurements did not reveal anymicrocracks in the workpiece and the error in dimension was in the range of-0.2to0.2mm. Compaired to the traditional thermal forming process, pulse currentauxiliary forming technique integrate pulse current heating with deep drawing and have many advantage including simple setup, high heating rates, lower energy lostand lower oxidation.The traditional bonding technologies can not arrived to ideal joint because ofthe bad bonding properties of SiCp/2024Al composites, which have importanteffects on safety and reliability of joints. Therefore, pulse current auxiliary transientliquid phase （TLP） bonding technology were studied, which utilized hith-intensitypulse current to get through Al-Cu-Ti powder interlayer and achieve the bonding ofSiCp/2024Al composites. Joule heat effect, electromigration effect, SPS can beproduced during pulse current auxiliary TLP bonding process. The microstructureand mechanical properties of joints of SiCp/2024Al composites were analysed. Theresults show the dense joints exhibite the uniform composition, good bonding qulity.In addition, in situ formation of Al₃Ti intermetallic phase in joints can induce theparticle dispersion strengthening and hindering dislocation sliding, which canprovide the mechanical properties of joints.The double-sheet structures of SiCp/2024Al were fabricated using pulsecurrent auxiliary transient liquid phase diffusion bonding technology. The resultsexhibited the joints show the metallurgical bonding between powder interlayer andaluminum matrix composites, which have no flaws including impurities, SiCparticle congeries and pores. The diffusion layers of Cu and Al₃Ti intermetallicphase were formed to guarantee the good qulities of joint. The mutle-sheetstructures of SiCp/2024Al composites were depended on the microstructure andmechanical properties of joints, but the worse qulity of joints of SiCp/2024Alcomposites restrained the development and application of the multi-sheet structuresof SiCp/2024Al composites because of oxidation film and SiC particle congeries.Pulse current auxiliary transient liquid phase diffusion bonding technology can beapplied to bond SiCp/2024Al composites sheet and promote the application ofmulti-sheet structures of SiCp/2024Al composites. Pulse current auxiliary transientliquid phase diffusion bonding technology with high-efficiency and lower energylost can promote development and application of multi-sheet structures ofSiCp/2024Al composites in future.