An investigation of phase boundary effect on the cutting force fluctuation in orthogonal micro-cutting of Ti6Al4V alloy

[Display omitted] •Variations of cutting forces occur at phase boudaries in machining Ti-6Al-4 V.•Force variations are related to the crystallographic orientation of workpiece.•The orientation, phase composition and slip systems on shear bands are varified.•Combining a constitutive model and geometric interplay between tool and workpiece.•Mechanism of boundaries effect on the cutting force variation is discussed. In micro-cutting, microstructure induced anisotropic properties highly affect the machinability of materials because the removal amount is almost on same level as the size of microstructures such as grains and phases. In this paper, cutting force fluctuation induced by different phases is theoretically and experimentally investigated in the micro-cutting of dual-phase Ti6Al4V alloy. Particularly, a significant change of cutting force was observed as the tool traverses phase boundaries. Furthermore, the mechanism of the variation of cutting forces is discussed from perspectives of crystallographic orientation, critical resolved shear stresses and slip systems. Constitutive model and geometrical relationship between the tool and workpiece are also proposed to analyzed the resolved shear stresses of phases with different crystallographic orientations. The results agree well with experimental data, indicating that activation of various slip systems is directly determined by the values of corresponding resolved shear stresses. Additionally, cutting force fluctuation is primarily attributed to the change of slip systems at phase boundaries in the micro-cutting. The main findings of this study present the significant role of crystallographic orientations and slip systems in governing cutting force fluctuations at phases and phase boundaries, which provide valuable insights for optimization of cutting parameters in machining of titanium alloys.