Research On Stress Corrosion Behavior Of 2A14 Aluminum Alloy Welded Joints

High strength aluminum alloys are widely used in national defense industry and national economy, and 2A14 aluminum alloy as a kind of high strength aluminum alloy, do have good machinability and forgeability.However, its corrosion resistance is poor.In the process of the use, 2A14 aluminum alloy may fail under the common action of the stress and the corrosion. Then accident will be caused. Although a lot of research work has been carried out on the stress corrosion of aluminum alloy, the research work on 2A14 is not yet complete.In the study of stress corrosion, it is hoped that the corrosion mechanism can be understood,the model of the relationship among the corrosion,stress,time and life is established, so as to ensure that the alloy is still safe to use.This article choose 2A14 aluminum alloy as the research object. 2A14 aluminum alloy has three parts:base metal, heat affected zone and the weld zone.They are conducted to different period corrosion in 3.5ωt% NaCl solution, using the way of constant load, combining with literature and experimental data,selecting 80% yield strength as load.By scanning electron microscopy(SEM) observed increased with time and corrosion morphology changes.Through the EDS analysis of the cracks near and the internal composition, the 2A14 aluminum alloy stress corrosion mechanism for anode dissolution.At the same time, the prefabricated stress corrosion crack and the welded joint specimen without prefabricated corrosion crack were tested by in situ tensile test under the SEM scanning electron microscope. The initiation and propagation of crack were observed.Finally, through data were collected by two test corrosion model, model proposed in this paper mainly consider the relationship between corrosion time and corrosion crack propagation, applicable to the constant loading conditions, has important scientific significance.The stress corrosion resistance of 2A14 aluminum alloy base is the strongest, and the weld zone is the second, and the heat affected zone is the weakest.2A14 aluminum alloy is Al-Cu-Mg-Fe-Si series alloy, containing Mg-Fe phase with respect to the aluminum matrix as the anode phase, anode dissolution occurs, the Cu phase with respect to the aluminum matrix as the cathode phase, so that the surrounding aluminum matrix occurs anode dissolution.In the base of the base metal, corrosion pits are first corroded. With the increase of corrosion time, intergranular corrosion is the main.Heat affected zone the number of corrosion pits and area compared with the same corrosion time of parent material area, with increasing corrosion time and corrosion pits gradually development is pitting corrosion, corrosion vertical depth of corrosion pits, pit morphology for honeycomb.Due to the original defects, the pitting corrosion pits and corrosion cracks are easy to be formed at the core of these defects, and the formation of exfoliation corrosion is formed.The heat affected zone and the weld zone were found to intergranular corrosion.2A14 aluminum alloy without prefabricated strain stress corrosion crack, in tensile force, the second phase particles first rupture, cracks are not easily extended to the aluminum matrix, only load is large enough, the micro crack together forming large cracks, the specimens at the main crack fracture, the main crack generally from the second phase particles in the middle of the fracture.For the precast stress corrosion cracking specimens, the precast cracks appear mostly in the original defects. These cracks extend along grain boundaries, and eventually lead to the fracture of the specimens.In this paper, the three corrosion morphology of the geometric model for measurin g the corrosion weightlessness, it is estimated that the proportion of different forms of c orrosion, and experimental data with good agreement. The residual life of the base meta l is determined by the combination of statistics and calculation method.