The present study reports on experiments and numerical simulations carried out to determine the wear and cutting performance of different polycrystalline diamond (PCD) tools in micro-end milling titanium alloy. The influence of tool geometrical parameters on wear resistance and machined surface precision was discussed. Furthermore, subsurface microstructure alteration was employed as an important index for evaluating the cutting performance of PCD tools. A dislocation dynamics-based multiscale framework, which is capable of promulgating the potential mechanism of above alteration, was adopted to quantitatively predict the evolution behavior of subsurface damages layer during micro-cutting process. The results demonstrated that the tool nose, flank and rake wear were of major wear forms and inappropriate tool structural changes can further accelerate tool failure. A PCD tool with rake angle of 5°, clearance angle of 15°, tool cutting edge radius of 20 μm and PCD granularity of 10 μm has highest cutting performance among the tested tools. Using this cutting tool, a surface roughness of Ra = 75nm better than most previously reported value on titanium alloy Ti-6Al-4V was achieved. A mass of subsurface damages consisted of discrete dislocation configuration, parallel glide lines and persistent slip bands were found after machining. Particularly, small tool cutting edge radius, large rake as well as clearance angle contributed to reducing defects quantity and decreasing the thickness of subsurface damages layer.

This article presents an experimental investigation on ductile-mode micro-milling of monocrystalline silicon using polycrystalline diamond (PCD) end mills. Experimental results indicate that the irregular fluctuation of cutting force always induces machined surface failure, even in ductile mode. The internal mechanism has not been investigated so far. The multiscale discrete dislocation plasticity framework was used to predict the dislocation structure and strain evolution under the discontinuous cutting process. The results showed that a mass of dislocations can be generated and affected in silicon crystal. The dislocation density, multiplication rate, and microstructure strongly depend on the milling conditions. In particular, transient impulse load can provide a great potential for material strength by forming dislocations entanglement structure. The continuous irregular cutting process can induce persistent slip bands (PSBs) in substrate surface, which would result in stress concentration and inhomogeneous deformation within grains.

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