Effect Of Friction Stir Processing On Microstructure And Mechanical Properties Of 6061 Aluminum Alloy

With the development of modern industry,the application of aluminum alloys has become more and more extensive,and it has become increasingly important to further increase the strength and plasticity of aluminum alloys.Friction stir processing can refine the grain of the material and increase its strength and plasticity.In this paper,the one-pass friction stir processing experiment is firstly carried out.Different rotating speeds,processing speeds,and shoulder pressures are selected.The 8 mm thick aluminum alloy in aging state is subjected to friction stir processing to study the friction stir zone under various parameters.The tensile properties give the highest friction stir processing parameters in the processing zone.Based on this,the 6061 aluminum alloy was subjected to three-pass friction stir machining,and the microstructure and properties of the 6061 aluminum alloy after three-pass friction stir machining were studied;and the solution 6061 aluminum alloys were respectively subjected to friction stir machining and aged 6061 aluminum.The friction stir machining of the alloy was compared to study the effects of different initial heat treatment conditions on the microstructure and properties of the friction stir processed 6061 aluminum alloy,and the best stirring friction machining process was obtained.The friction stir machining was compared with 6061 aluminum alloys of different deformation amounts cold-rolled.Hot-extruded 6061 aluminum alloy was subjected to one-pass friction stir machining.When the rotating speed was 1200 r/min,the processing speed was 90 mm/min,and the reduction was 1 mm,the grain size decreased from 110 μm.Below 20 μm(friction stir area),the tensile strength,yield strength,and elongation are 346 MPa,182 MPa,and 24.7%,respectively.After aging treatment at 180℃ for 6 h,the tensile strength,yield strength and elongation were 397 MPa,316 MPa and 13.2%,respectively.The fracture mode in the agitation zone was a ductile,microporous aggregate fracture.After three-pass friction stir processing,the grains in the agitation zone are even and fine,with a tensile strength of 404 MPa and an elongation of 13%.The artificial aging treatment reduces the difference between the performance of different passes of friction stir processing,especially the factors that lead to the plasticity difference of the materials,so that the elongation of the materials processed by different friction stir processing is basically the same after aging treatment.The friction stir processing of 6061 aluminum alloys with different pretreatments was carried out.After solid friction 6061 aluminum alloy was processed by friction stir pocessing,a relatively obvious hole-type defect was found in the cross-section of the processing zone;however,the 6061 aluminum alloy did not show this defect in the aged 6061 alloy..The tensile strength,yield strength,and elongation after solid friction treatment of 6061 aluminum alloy in solid solution state are 337 MPa,180 MPa,and 25.79%.After peak aging at 180℃×6 h,the tensile strength,yield strength and elongation of the stirred zone were 399 MPa,326 MPa and 15.23%,respectively.The 6061 aluminum alloy was cold-rolled.As the cold-rolled deformation increased,the grains shattered,high-density dislocations were formed in the structure,and the hardness increased.When the deformation amount is 80%,the tensile strength,yield strength and elongation are 357 MPa,315 MPa,4.7%,respectively;560℃×2 h solution treatment + 80% cold deformation + 180℃ × 5 h aging treatment After the deformation heat treatment,the tensile strength,yield strength and elongation were 368 MPa,330 MPa,and 4%,respectively.