Analysis of cutting forces and surface quality during micro milling of AZ31B magnesium alloy

Magnesium alloys have attracted significant research attention due to their impressive mechanical properties, such as machinability, a high strength-to-weight ratio, and low density compared to aluminium and steel. Due to the above properties, Mg alloys have a wide range of applications in the field of biomedical applications such as vascular stents and fixatives, aircraft fuselage, micro-electro-mechanical systems (MEMS), and automotive industries. The current work focused on the performance of uncoated and AlTiN-coated micro end-mill cutters having a diameter of 0.5 mm and two flutes in the development of machined surface morphology of AZ31B magnesium alloy and the analysis of cutting forces under the varying spindle speeds of 20,000, 40,000, and 65,000 rpm and feeds of 0.5, 2, and 4 mu m/tooth. In general, the results indicated that the uncoated tools consistently resulted in lower values of cutting forces (Fx, Fy and Fz), and surface roughness than with AlTiN-coated tools under all conditions of machining. This could be attributed to the increase in cutting edge radius due to the deposition of the coating resulting in rubbing and ploughing to become predominant. Adhesion of work materials during machining using the AlTiN-coated tool was explained by the chemical affinity of aluminium of the coating towards Mg alloys. After careful analysis of the results, relatively low cutting forces were noticed, and due to the absence of tool wear, there was no significant variation in surface roughness with an increase in cutting length up to 60 mm.