Effects of grains and twins on deformation of commercial pure titanium in ultraprecision diamond turning

This paper theoretically and experimentally analyses and discusses the material deformation mechanism of commercial pure titanium (CP Ti) in ultraprecision machining. One sample with two obviously diverse microstructures is first obtained by compressive test followed by electropulsing treatment (EPT) for 30 s. Then, ultraprecision diamond turning was conducted on the specimen to investigate the effects of grains and twins on the microcrack nucleation and deformation behaviour during cutting process. The results show that microcracks primarily nucleate in large grains and thick twins rather that small grains or twins. Furthermore, critical resolved shear stress (CRSS) and barrier stresses induced by grain or twin boundaries and dislocations are introduced in the proposed model, which not only compares the deformation difference between grains and extension twin of 101¯2 type, but also simulates the relationship between resolved shear stresses, cutting shear angles, strain rates and temperature for the first time in ultraprecision diamond turning.