MICROSTRUCTURE OF Al_2O_3 ANODIC HARD COATINGS ON EN-AW5251 ALUMINIUM ALLOY OBTAINED BY PULSE METHOD

摘要

This paper presents the possibility of modifying the microstructure of anodic hard coatings on aluminium alloys by applying a pulsed method in the process of their electrochemical deposition. Anodic hard coatings were formed on an aluminium alloy intended for plastic working. The electrolytic process was conducted using the pulsed method with a rectangular current waveform in time, applying variable frequencies, current densities and duty cycles of the waveform. Examination of the microstructure of the anodic hard coatings was carried out by image analysis of the images obtained by means of SEM from fractures of the coatings. The obtained results indicate that the application of the pulse anodizing method results in the occurrence of local changes in the microstructure of the anodic hard coatings.