Microstructural effects of ECAP-induced grain refinement on the ultraprecision machining behavior and material removal mechanism of TA2 commercially pure titanium

Grain refinement by severe plastic deformation is an effective approach for improving the performance of metallic materials. However, its influence on the ultraprecision machining behavior of commercially pure titanium (CP-Ti) remains unclear. In this study, TA2 CP-Ti specimens with different grain sizes were fabricated by equal-channel angular pressing (ECAP). The microstructural evolution and its effects on ultraprecision machining performance were systematically investigated. The results show that the average grain size was refined from approximately 10 μm to 1.3 μm after 16 ECAP passes. Meanwhile, continuous dynamic recrystallization, assisted by dislocation slip and deformation twinning, was identified as the primary grain-refinement mechanism, leading to enhanced hardness and compressive strength due to combined strengthening effects. Ultraprecision machining experiments reveal that the cutting force increases with decreasing grain size, whereas the machined surface roughness decreases under identical cutting conditions. This behavior is attributed to the dual effect of grain refinement: the increased grain-boundary density enhances the resistance to plastic deformation, while the more homogeneous ultrafine-grained microstructure promotes stable material flow and suppresses localized deformation. These findings establish a direct relationship between ECAP-induced microstructural evolution and ultraprecision machining performance, providing guidance for the microstructural design and precision manufacturing of titanium-based components.