X-ray and Nanoindentation Analyses on Plastic Deformation of Galvannealed Coating

Abstract

Using galvannealed steels rolled at various temperatures (∼100°C) and to various reductions (∼50%), plastic deformation in galvannealed coating layer was evaluated by scanning electron microscopy, X-ray diffraction for measuring half width value of diffraction peaks, and nanoindentation test. By rolling deformation, the thickness of the coating layer plastically decreased and its reduction became more remarkable at high temperature deformation, suggesting that macroscopic plastic deformation takes place in the coating layer. The plastic strain evaluated by X-ray diffraction parabolically increased with increasing rolling reduction in both layers of δ₁ phase and Γ phase, but more significant in δ₁ phase than in Γ phase. The F-h curves drawn by nanoindentation test indicate that the plastic deformation is more significant in order, α-Fe substrate>δ₁ phase>Γ phase. Also, Vickers hardness results obtained by nanoindentation test showed that hardness is higher in order, Γ phase>δ₁ phase>α-Fe substrate. Consequently, the Vickers hardness of each phase in the coating layer evaluated by nanoindentation was irreversibly correlated well with the plastic deformability of each phase in the coating layer evaluated by F-h curves and X-ray diffraction.