Purpose -The purpose of this paper was the investigation of corrosion behaviour of Ni-6Al-10Cu-11Fe-15Cr alloy, as a candidate material for inert anodes in aluminium electrolysis industries. Design/methodology/approach -The samples were prepared by casting, and then were oxidized at 1,000°C for 30, 70 and 100 hours, respectively. To determine corrosion resistant of the samples, they were exposed to molten cryolite at 930°C for 70 hours. Then the surface layers were studied. Findings -Results showed that by extension of corrosion time, thickness of oxide layers increases. In addition, it was found that Al2O3 and Cr2O3 are the major oxide compounds that appear on the surface of the sample. Originality/value -In this paper, the Ni-6Al-10Cu-11Fe-15Cr nickel base alloy has been selected to study its corrosion behaviour in molten cryolite as a candidate for inert anodes. It was found out that by addition Al and Cr into the alloy composition, due to formation of Al2O3 and Cr2O3 following oxidation, the substrate was protected from corrosion attacks.
In this paper, the effect of surface oxidation on corrosion behaviour of Co-20?8Ni-6Al-10Cu-11Fe alloy in molten cryolite is investigated. The samples were produced by casting and then were oxidised at 1000uC for 10, 30 and 70 h respectively. The oxide layers were studied by scanning electron microscope (SEM) and X-ray diffraction (XRD). To determine the corrosion behaviour of the oxidised samples, they were exposed to molten cryolite at 930uC for 20 h. After corrosion, the samples were studied by SEM. The results showed that all the samples corroded, but the sample oxidised for 70 h, was more stable than the other and the other one that oxidised for 10 h, corroded severely.
Vibratory weld conditioning (VWC) was performed on the AA-5083 aluminum alloy specimens while they were welded with gas metal arc welding (GMAW). The variables in this study were vibration forces range from 400-3150 N and vibration frequency of 50-90 Hz. Microstructure, residual stress, and fatigue crack growth behavior of the welded samples were examined. Fracture analysis was also undertaken after the fatigue crack growth test using a scanning electron microscope (SEM). The results show that compared to the no-vibration welded sample, with increasing vibration forces, the columnar structure was replaced by equiaxed grains, and the area fraction of equiaxed grains increased to 75 %. In contrast to the sample welded without vibration, residual stress decreased while vibration was applied during welding. On the other hand, the application of mechanical vibration during welding, at each given frequency of 50, 75, and 90 Hz caused residual stress decrement of about 36, 38, and 44 %. At low ΔK values, the crack growth rate is low in all welded specimens and is approximately similar to the crack growth rate of the no-vibration welded specimen. Tensile residual stress is an effective reason that caused the crack growth rate of the material to increase. K e y w o r d s : vibratory weld conditioning (VWC), equiaxed grain, residual stress, 5083 aluminum alloy, fatigue crack growth
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