Author(s)

HERMAN FIDDER, VACLAV OCELIK, JEFF. TH. M. DE HOSSON

Abstract

The effects of microstructure transformation during forming processes viz. Mechanical (contact process via tool and die), laser (contactless process via CO₂ laser defocused beam) and a combined process consisting of laser forming followed by mechanical forming was analysed before and after each process. Plastic flow during the deformation is strongly influenced by anisotropy and the work hardening rate, which is due to the limited number of slip planes in a hexagonal close-packed material. Commercially pure titanium can exhibit dominant twinning systems during deformation when either tensile or compression is introduced. Electron backscatter diffraction (EBSD) results show multiple dominate pyramidal slip behaviours due to the lattice rotation when comparing the before and after deformation processes. The Schmid factor and twinning parent/daughter ratios for each individual grain after each forming process were also evaluated. Our findings show twin nucleation and twin growth also contribute a major role when observing the nature of the microstructure for each process.

Keywords

commercially pure (CP) titanium, laser forming, EBSD, twinning, pyramidal slip