Influence Of Dwell-time And Prestretching Deformation On The Microstructure And Properties Of Aluminum Alloy7B04

Abstract:Influence of short-term dwelled aluminum alloy7B04cold rolled sheet with the thickness of2mm after quenching and the prestretching deformation on its organization and performance were investigated by using Hardness, Electrical conductivity, Tensile property, Opical Microscopy (OM), Scanning Electron Microscope (SEM), Transmission Electron Microscopy (TEM). The main conclusions are as follows:(1) The hardness、tensile strength and yield strength will gradually increase with the dwell-time after quenching, while the electrical conductivity and the elongation decrease. Within2h after quenching, the properties of aluminum alloy7B04nearly unchanged; After4h, the change begin to rapidly growth;48h later, all properties show stablization; As time goes on, it show little increments. After quenching for72h, the tensile strength and yield strength will be increased from350MPa and170MPa in early stage to170MPa and250Mpa, but elongation will be decreased from21.5%to20%.(2) With increasing of the pre-defromation, the time for aluminum alloy7B04cold-rolled sheet to reaching its peak strength has been significantly shortened. The time for reaching the peak strength of the sample with pre-deformation for3%,5%,7%and5%has been advanced for18h、14h、10h、8h, respectively from24h. Peak strength of aluminum alloy7B04cold rolled sheet increase with pre-deformation, elongation is decreased with the increase of the pre-deformation.(3) High densities of dislocations are generated in the pre-stretching of aluminum alloy7B04. With the increase of the prestretching deformation, the dislocation in alloy and its density increased significantly.(4) By measuring the conductivity and the polarization curve after quenching, with the extension of dwell-time, With the extension of dwell-time, corrosion potential and corrosion current density of aluminum alloy7B04increases. After quenching for48h, the corrsion potential and corrosion current density will be increased from-529mV and1.10E-06A after dwelled24h to-482mV and2.63E-06A.(5) Acorrding to the result of electrode potential, the order of corrosion potential from large to small of the sample with0%,3%,5%,7%and9%predeformation under peak-aging show as:0%pre-stretching samples>5%pre-stretching>9%pre-stretching>3%pre-stretching>7%pre-stretching; The order of the corrosion current density from large to small as follows:0%pre-stretching samples>7%pre-stretching>5%pre-stretching>9%pre-stretching>3%pre-stretching.(6) After single-aging at120℃, the spalling corrosion resistance of aluminum alloy7B04gradually increase with pre-deformation.