Investigation of microstructure, wear and seawater corrosion performance of T6 and deep cryogenic heat treated aluminum based magnesium alloys

In this study, T6 (solution and aging) heat treatment followed by deep cryogenic (DC) heat treatment was applied to AZ91 and AM60 magnesium alloys. Solution heat treatment was carried out at 400°C for different times (4, 5 and 6 hours). Heat treatment in aging was carried out by annealing in an oven at 200°C for 10 hours. After these processes, the samples were subjected to deep cryogenic (DC) heat treatment at -196°C for 48 hours. In order to measure the wear resistance of the samples, the pin-on-disc method and the corrosion resistance were measured by performing electrochemical experiments in an aqueous solution containing 3.5% NaCl by weight. In the obtained findings, it was observed that the microstructure of AZ91 and AM60 changed after heat treatment. For AZ91, it was observed that the eutectic phase dissolved more in the matrix, on the other hand, in AM60 alloy, after 4 and 5 hours, excluding 6 hours, the eutectic phase dispersed in the microstructure and dissolved in the matrix. It was determined that while the wear rate increased with time in the AZ91 alloy, it decreased after 5 hours in the AM60 alloy. In corrosion studies, the open circuit potential (Eocp) of the untreated AZ91 alloy was found to be more positive than the heat treated samples. On the other hand, it was observed that Eocp increased positively with the increase of T6 heat treatment time in AM60 alloy. In addition, it was understood that no passivation zone was formed in the polarization curves obtained for the heat treated or untreated AZ91 and AM60 alloys.