Transmission electron microscopy (TEM) study of anisotropic surface damages in micro-cutting polycrystalline aluminate magnesium spinel (PAMS) crystals

The synergy of anisotropy within each single-crystal grain and high brittleness of polycrystalline aluminate magnesium spinel (PAMS) leads to its poor machinability and regional surface damages. The mechanism of the featured cracks is first studied with transmission electron microscopic (TEM) observation beneath the machined surfaces of two adjacent grains with different surface integrities. The comparison of Schmid factors of both grains signifies that the activity of the slip systems is responsible for ductile or brittle cutting mode. The cooperation of lattice gliding on the slip planes and the irreconcilable slip directions with the compulsive cutting motion leads to the anisotropic damage patterns.