2020 Volume 106 Issue 5 Pages 244-253
This research centers on elucidating the relationship between void nucleation sites and the morphology/distribution of the surrounding phase in dual-phase steel during the initial stages of ductile fracture. Characteristic features of voids and surrounding ferrite/martensite grains were observed through a three-dimensional (3D) optical microscope analysis with the aid of serial sectioning. The characterized 3D distribution and morphology of ferrite/martensite surrounding the voids were set as an input for a finite flement (FE) simulation to obtain the hydrostatic pressure and equivalent plastic strain in the ferrite and martensite phases during tensile deformation. Experimental results showed that some of the voids present in the ferrites were surrounded by the flat-shaped martensites, which were elongated along both rolling direction (RD) and transversal direction (TD). These flat-shaped martensites were existed along the tensile direction. The FE simulation showed that the ferrite grains sandwiched between the harder martensites are more susceptible to void nucleation; this is due to the concentration of equivalent plastic strain and hydrostatic pressure in the ferrites during tensile deformation.