Study of the corrosion resistance of aluminum alloy AMg6 and steel 12Kh18N10T in conditions of loading under the impact of environmental factors

Stress corrosion cracking is one of the most dangerous types of corrosion damage in metallic materials. We present the results of studying the impact of environmental factors on the susceptibility of AMg6 aluminum alloy and 12Kh18N10T stainless steel to stress corrosion cracking under four-point bending. Tests of loaded samples were carried out in laboratory and field conditions of the moderately warm climate of the coastal zone over a period of six months. The samples were examined daily with fixation of the time to their destruction and upon completion of the tests the appearance of the samples and the depth of intergranular corrosion on microsections were assessed. A 3D relief was constructed using macro photography of the surface with the determination of the depth of corrosion foci. We also carried out a comparative analysis of the frequency of stress-induced destruction of steel samples of various grades both in atmospheric and laboratory conditions. It is shown that in atmospheric conditions characterized by the presence of dust particles acting as concentrators for the formation of corrosion foci, the aggressiveness of the corrosive effect of the environment increases, whereas the general corrosion resistance of materials decreases. The most pronounced effect of the environment was recorded in AMg6 alloy samples when exposed under a ventilated canopy in conditions of periodic spraying of seawater aerosols. The depth of surface corrosion damage was up to 0.1 mm. When the test samples were exposed under other conditions (salt fog chamber and louvered storage) the corrosion damage was absent. The results obtained can be used to predict the corrosion resistance of the products made of AMG6 alloy and 12Kh18N10T steel when operated in conditions of loading under the impact of environmental factors.

Stability of Strength Characteristics of Hardened by Deformation AMg6 Alloy during High-Speed Heating

The results were shown in influence of fast heating parameters on the structure and properties of cold-worked alloy AMg6 with original hot-forged structure. Based on the measured data, the change of mechanical properties of cold-worked alloy AMg6 during the process of short duration heating was evaluated. There was reviewed the role of the temperature and the time of heat on the processes of softening the samples of cold-worked alloy AMg6. The stability of mechanical characteristics of hammer-hardened alloy AMg6 under elevated test temperatures was evaluated. It is shown that the return processes in cold-deformed AMg6 alloy during heating in the temperature range studied receive the most intensive development in the first 5–10 minutes, reducing the hardening effect from cold deformation, determined by tensile strength, respectively: by 8–9% with 100 °C; 26–27% at 150 °C; 37–38% at 200 °C; 42–44% at 250 °C and 50% at 300 °C. A decrease in the yield strength during high-speed heating in the temperature range studied is much faster ,compared with the change in the tensile strength. Hour exposure at 200 °C reduces the hardening effect on the yield strength from 340 MPa to 258 MPa, while the tensile strength decreases from 430 MPa to 385 MPa.