Cutting mechanism of Mg-Li-Al alloys

The effect of Li content on the cutting mechanism of Mg-Li-1 mass%Al alloys containing 5, 8 and 16 mass%Li has been investigated by both cutting force measurements under orthogonal cutting and microscopical observation. The magnitude of the cutting force increased with increasing the additional element of Li, and was found to change in the order of rake angle, π/18 > π/9 > π/6 rad. The estimated shear angle from cutting ratio decreased with increasing Li content. The chip form and machined surface roughness indicated that the chip formation processes were a shear chip type cutting and a continuous chip type cutting for a 5%Li alloy and for 8 and 16%Li alloys, respectively. In the 16%Li alloy giving high cutting force, a crack located in front of tool tip was observed on the quick-stopped microstructure. This was explained by the fact that the grain size of the 16%Li alloy was not fine enough compared with the depth of cut.