Quantifying lamellar microstructural effect on the fatigue performance of bimodal Ti-6Al-4V with microdefect

•Coordinated effects of LM and microdefect on fatigue behavior of Ti-6Al-4V is studied.•A weight approach is proposed to account for intragranular accumulative deformation.•Parametric ADI is defined to relatively quantify the lamellar microstructural effect.•Increase of β lath and synchronized refinement of intragranular LM improve LM effect. Fatigue performance of metal alloys is inseparably associated with heterogenous microstructure and existing microdefects. The coordinated effects of lamellar microstructure (LM) and microdefect on fatigue performance of bimodal Ti-6Al-4V is studied within the framework of CPFEM. We propose an intragrain weight integration approach able to account for intragranular accumulative deformation. Parametric accumulative difference indicator (ADI) for stress is defined to relatively quantify the lamellar microstructural effect, overcoming the limitations of experimental procedures. The results demonstrate that the increase of β lath and synchronized refinement of LM appreciably improve lamellar microstructural effect. These attributes can be applied to the material design and manufacturing of advanced metal alloys.