Surface Roughening and Deformation of Grains during Uniaxial Tension of Polycrystalline Iron.

Abstract

Changes in the surface roughening and the inhomogeneous deformation behavior of respective grains of polycrystalline iron during uniaxial tension are experimentally investigated. The shape of the roughened surface is measured three-dimensionally at each step of the tensile deformation. The profiles of respective grains are obtained from a photograph of the scanning electron microscope, and the principal strain of the grain is calculated from the axis of the approximated ellipse of the strain distribution of the grain. Thus, the relation between the change in the roughened surface and the deformation of grain is discussed. It is found that the surface roughness proportionally increases with the applied strain until the necking becomes obvious. The amplitude of the surface roughness grows, and the mountains of the roughened surface elongate in the axial direction during tensile deformation. On the other hand, the respective grains continue to deform during tensile deformation, though the increase ratio of the maximum principal strain is different for individual grains. These results mean that the surface roughening is closely related to the mutual rotation of grains, and the roughness grows due to the difference in the deformation behavior of respective grains.