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

Changes in the three-dimensional (3D) shapes of roughened surfaces and the inhomogeneous deformation behaviors of individual grains during uniaxial tension of polycrystalline iron are experimentally investigated. The principal strains of each grain are evaluated by obtaining the approximated ellipse of the strain distribution of the grain, and then the relationship between the change in surface roughening and grain deformation is discussed. It is found that the mountains and the valleys of the roughened surface elongate in the axial direction with increasing amplitude during uniaxial tension. The grains continue to deform with the applied strain, though the rate of increase of the maximum principal strain differs among grains. From the comparison between the roughening phenomenon and the deformation of grains, it is found that surface roughening is closely related to the mutual rotation of grains. Thus, roughness increases due to the different deformation behaviors of individual grains.