Effect of aluminum content on machining characteristics of AZ31 and AZ91 magnesium alloys during drilling

Magnesium (Mg) and its alloys are now becoming the promising choice for various structural applications due to their low density and high specific strength compared with other light metals such as aluminum and its alloys. Among all Mg alloys, AZ (aluminum and zinc) series is the most widely used alloy system for various structural applications. But, machining of magnesium and its alloys involves certain issues due to their brittle nature and risk of inflammability unlike other nonferrous metals. Particularly, alloys with considerable amount of secondary phase may exhibit different machining characteristics during metal cutting operations. In the present study, two AZ series alloys AZ31 and AZ91 were selected and drilling operation was performed to assess the effect of the secondary phase amount and distribution on machining characteristics. Drilling operation was carried out at different sets of process parameters and cutting forces were obtained and the chips which have been produced during drilling were analyzed. From the results, it can be clearly understood that the presence of secondary phase (Mg17Al12) has a significant influence on cutting forces. Increase in cutting speed has reduced the required cutting force and load fluctuations in all the cases.