Effect of cutting parameters on the microstructure evolution and damage mechanism of 7075-T6 aluminum alloy in micro cutting

This work aims to explore how cutting parameters affect the microstructure evolution and damage mechanism of 7075-T6 aluminum alloy in micro cutting. The effect of cutting parameters on micro cutting force and surface morphology is examined through single-factor test. By building a 3D micro finite element model for micro cutting based on crystal plasticity theory, the effect of cutting parameters on residual stress, microstructure evolution and damage behavior is analyzed to establish a mapping relation between residual stress and damage. The results show that as cutting speed increases, main cutting force first reduces then increases in all cases, but the cutting speed at the inflection point corresponding to main cutting force is different. The micro cutting surface morphology of 7075-T6 aluminum alloy displays obvious signs of plowing; detectable oxidation adhesion wear appears when the cutting depth is greater than 150 μm. Crack initiation and propagation on the machined surface of 7075-T6 aluminum alloy vary considerably under different cutting parameters. Residual stress distribution displays a ladle profile. The deeper the maximum residual compressive stress is from the surface, the harder it is for micro cracks to initiate and propagate. SEM and EDS analysis indicates that at smaller cutting depths, micro cutting tool wear is dominated by oxidation wear; at larger cutting depths, surface morphology is mostly better than at smaller cutting depths.