Effects Of Electric Current On Microstructures And Properties Of 7B04 Alloy During Solution And Aging Treatments

In present work,hardness test,conductivity test,the tensile test,optical microscopy,scanning electron microscopy,X-ray diffraction analysis and differential scanning calorimetry(DSC)thermal analysis were used to investigate effects of electric current on microstructures and mechanical properties of 7B04 alloy during solution and aging treatments.This paper futher probes into the influence of current field on phase transformation and activation energy of 7B04 alloy during solution and aging treatments by the use of thermodynamic principle.The main conclusions are as followings:(1)With increasing the solid solution temperature and the current intensity,the hardness and the tensile strength increase,while the conductivity decreases.When the alloy is solutioned at 470? with direct current of 1000A,the hardness,the tensile strength and the conductivity were 125.3HV,627.9MPa and 27.1%IACS,respectively.(2)Increasing the aging time and the current intensity could promote the nucleation of precipitates and improve the conductivity.The conductivity of alloy reached the peak when aging at 120? for 24h with 600A direct current(DC),and it was 30.7%IACS.(3)During the aging treatment,applying current(100-300A)could improve the tensile strength,lengthening the application time until the alloy reached aging peak.When the current intensity is 600A,the tensile strength decreases and the application time shortens.During aging treatment without current,the alloy reached aging peak when the aging time is 12h.The tensile strength,yield strength and elongation were 671.5MPa,601.3MPa and 11.6%,respectively.During aging treatment with direct current of 100A,the alloy reached aging peak when the aging time is 24h.The tensile strength,yield strength and elongation were 708.0MPa,652.1MPa and 11.5%,respectively.(4)The DSC analysis results showed that increasing the current intensity can accelerate the transformation of solute-rich regions to ?' phase and ? phase,and increase the enthalpy of ?' phase and ? phase during solution treatment.When solutioned at 470?/1000A,the alloy achieved the maximum enthalpy of ?' phase and ? phase.It was 29.8J/g.(5)Increasing the current intensity could increase the enthalpy of ?' phase and? phase,decrease the activation energy during aging treatment.During aging treatment without current,the enthalpy and the activation energy were 3.8J/g and 313.7kJ/mol.When aging at 120? for 12h with 600A DC,the alloy achieved the maximum enthalpy and the minimum enthalpy of ?' phase and ? phase.They were 6.9J/g and 162.9kJ/mol,respectively.