Surface Quality of AZ91D Magnesium Alloy After Precision Milling with Coated Tools

This study investigates the surface quality of AZ91D magnesium alloy specimens after precision milling. The milling was conducted with the use of TiB2- and TiAlN-coated carbide end mills. The following variables were used in the milling process: cutting speed vc, feed per tooth fz and axial depth of cut ap. The surface quality was analysed based on surface roughness parameters and Abbott-Firestone curves. The results showed that the surface quality after machining depended on the tool coating type and applied machining parameters; the only exception was the axial depth of cut because changes in its value did not have any significant effect on the obtained surface quality. After precision milling, AZ91D specimens were characterized by very low surface roughness parameters. The impact of machining conditions was also evaluated with ANOVA analysis, which confirmed the significant effect of cutting speed and feed per tooth. It also indicated the dependence of the roughness parameters on the tool coating type. The tool coating type and machining conditions did not have any significant effect on the Abbott-Firestone curves. Despite the changes applied, the shape of the curves remained similar. The obtained results provide both theoretical and practical knowledge about the achievable surface roughness of AZ91D magnesium alloy specimens after precision milling.