Study On Microstructure And Mechanical Properties Of Al-based Composites Prepared By Cumulative Rolling Welding

Cumulative Rolling Welding has the advantages of simple process,easy operation,easy popularization,high production efficiency and the like,is suitable for assembly line production,and has wide industrial prospect.In this paper,two kinds of metal materials are subjected to multi-pass deformation rolling by the cumulative rolling welding process to prepare multi-layer aluminum matrix composites.The microstructure,phase composition,fracture morphology and tensile properties of the samples were observed and studied by optical metallographic microscope,X-ray diffractometer,scanning electron microscope and universal mechanical testing machine.A mathematical model has established to analyze the constitutive relation of aluminum matrix composites at different elastic-plastic stages and the correlation between Cumulative Rolling Welding passes and work hardening index.The results show that with the increase of rolling times of aluminum-iron composite plates,the bonding between the plates is gradually tight,and the bonding interface disappears.The difference between the holding time and the substrate has an important influence on the bonding of the substrate.The bonding interface of 1060/Fe/1060 based composite board disappeared basically after 60 minutes of heat preservation at 300?,and the aluminum-iron interface disappeared after 60 minutes of heat preservation at 300?.No new phase or intermetallic compound was detected at the bonding interface by XRD and scanning electron microscope.After the second rolling,the accumulated real strain is 1.39,the tensile strength reaches 175 MPa and the yield strength reaches 140 MPa,which is 68.3% and 35.9% higher than that of the matrix material respectively.After each pass of rolling,6061/Fe/6061 is kept at 300? for 5 minutes,and the aluminum-iron bonding interface has the same properties as 1060/Fe/1060.After the third rolling,a large number of microcracks appeared in the matrix.As the rolling proceeded,the cracks gradually decreased,and the tensile strength and yield strength reached 20 with the best comprehensive performance,which increased 38.41% and 23.8% respectively compared with the matrix.After 6061/TC4/6061 is rolled and deformed at 300?,compared with the rolling state at room temperature,the plasticity of the material is improved,so that the bonding interface obtained by increasing the relative deformation is straighter,the stress is not easy to concentrate,and the tensile strength is higher than that of the rolling at room temperature.The third pass has the best comprehensive mechanical properties,with the tensile strength reaching 430 MPa,162.20% higher than that of 6061 aluminum alloy.Fe-based amorphous alloy disperses and distributes in the matrix in the form of fragment inclusions,and the fragment distribution of amorphous Fe-based alloy becomes finer and more uniform along the plastic flow direction with the increase of rolling passes.With the increase of deformation,both 1060/Fe/1060 and 6061/Fe/6061 composites show softening phenomenon.In the elastic-plastic deformation stage,when the accumulated true strain of 1060/Fe/1060-based composite material reaches 4.16 through the sixth pass of rolling,the energy absorbed in the elastic deformation stage is the largest,and its specific work of elasticity reaches 13.76 GPa.When the accumulated strain reaches 4.85 through the seventh pass of rolling,the energy absorbed,elastic modulus and work hardening index reach the maximum respectively,reaching 455.68 GPa.The elastic modulus and work hardening index of 32.6GPa and 0.79,1060/Fe/1060 composites increase with the increase of accumulated true strain during ARB.When the accumulated strain of 6061/Fe/6061 composite material reaches 1.16 after two passes of rolling,the specific work of elastic modulus and elasticity are 28.2GPa and 11.24 GPa respectively,and when the accumulated true strain of 6061/Fe/6061 composite material reaches 3.46 after five passes of rolling,the work hardening index reaches 0.40.As the plasticity of the material decreases due to microcracks generated during rolling,the maximum specific work of ARB for the sixth pass of breaking reaches 938.03 GPa,which is still lower than that of matrix 6061.Compared with room temperature rolling state,the plasticity of 6061/TC4/6061 composite material rolled at 300? is improved,and the third elastic specific work of the sample rolled at 300? is the largest,reaching 120 GPa.After the first pass of rolling at room temperature,the non-aged state has the largest fracture specific work,which is 3176 GPa,indicating that the state has good plasticity.Due to the non-uniform plasticity between heterogeneous metals,the titanium layer and the aluminum layer are necked to different degrees.At this time,under the action of tangential stress,the joint surface is separated and the weak connection formed at the interface is destroyed.Fe-based amorphous alloy foil strip and annealed TC4 sheet have be both used as reinforcements to enhance 6061 aluminum alloy.Compared with TC4 continuous reinforced aluminum matrix composite,the Fe-based amorphous alloy foil strip discontinuous reinforced aluminum matrix composite has a tighter bonding effect between substrates,but TC4 has a more significant effect on improving the strength of Al matrix due to the larger volume fraction of TC4 sheet and continuity during rolling.TC4,as a reinforcement,broke during the fourth pass of room temperature rolling,resulting in a sharp drop in the strength of the composite.Therefore,improving the bonding strength between dissimilar metals while maintaining the continuity of the reinforcement through process improvement is the only way to strengthen and develop the dissimilar metal laminated composite.