Effects Of Electric Current On Microstructures And Properties Of 6061 Alloy During Homogenization,Solution And Aging Treatments

6061 alloy belongs to heat-hardening aluminum alloy.In this paper,steady current was applied directly to the 6061 alloy sample with the use of current field heat treatment furnace researched independently.Combined with microstructural observations,EDS analysis,XRD analysis,DSC analysis,hardness,conductivity and tensile tests are carried out to investigate the effects of current on phase dissolution,precipitation behavior and mechanical properties of 6061 alloy during homogenization,solution and aging treatments.The conclusions are as followings:Increasing the homogenization temperature and applying current can increase the hardness,decrease the conductivity,promote the dissolutions of ?-AlFeSi phase and Mg2Si phase,accelerate the transformation of ?-AlFeSi phase to a-AlFeSi phase,and decrease the area fraction of residual phases.When homogenized at 560?,the 6061 alloy achieved the maximum hardness,minimum conductivity and area fraction of residual phases.When 500A alternating and direct current was applied separately during homogenization,the hardness increased by 8.10HV and 16.30HV,conductivity decreased by 0.80%IACS and 1%IACS,and the residual phase area fraction reduced by 0.184%and 0.241%respectively.With increasing the solid solution temperature,the hardness increases,while the conductivity shows a decreasing trend firmly.The hardness of 6061 alloy solid solution with current is higher than the conventional solid solution treatment,and the hardness of 6061 alloy with direct current is higher than that of alternating current The optimum solid solution treatment for 6061 alloy is solutionized at 550? with direct current of 500A for 30 minutes,and the hardness is 101.10HV,conductivity is 39.80%IACS,tensile strength is 229.20MPa and elongation is 30.40%.With increasing the aging time,the hardness and strength first increases and then decreases,while the elongation decreases firmly.The hardness,conductivity and strength increased,elongation decreased for aged 6061 alloy when alternating or direct current was applied during solid solution treatment.The optimum T6 heat treatment for 6061 alloy is solutionized at 550? with direct current of 500A for 30 minutes and aged at 170? with direct current of 500A for 12h,and the tensile strength is 349.67MPa,elongation is 13.10%,hardness is 140.50HV and conductivity is 44.00%IACS.The DSC analysis results showed that solid solution with alternating or direct current can increase the precipitation volume fraction of ?" phase,reduce the activation energy of precipitated phase.The activation energy of ?" phase decreases by 1.69KJ/mol,12.66KJ/mol respectively.Applying current in the solution process not only increases the extent of supersaturated concentration,but increases the precipitation impetus of the second phase during the aging process,which promote to the precipitating of more smaller strengthening phases.