Quantification of local plastic strain distribution beneath surface of deformed iron

Effects of indentation depth and the strain rate on the local plastic strain distribution in the depth direction beneath the deformed iron surface have been studied by means of ball-dropping (high strain rate) and ball-pressing (low strain rate) tests. Evaluation of the local plastic strain was conducted by using the electron backscatter diffraction (EBSD) analysis. It was indicated that large macroscopic plastic strains with high strain rates lead to steep and narrow distribution profile of local plastic strain. The peak of the local plastic strain profile does not appear at the deformed surface but immediately beneath the surface. The deformation at high strain rates is favorable to localize the plastic strain in the vicinity of the surface. On the other hand, the deformation at lower strain rates makes plastically deformed zone wider.