Investigating the relationship between grain orientation and surface height changes in nickel polycrystals under tensile plastic deformation

This paper investigates the effect of the grain orientation on the surface roughening of nickel polycrystals undergoing plastic tensile deformation. Both experimental and simulation work was carried out. In the experiments, we measured the surface topography at different strain levels. The surface topography images were analyzed to classify individual grains as either rising or sinking. In simulations, we utilized a Crystal Plasticity Finite Element model that embeds a grain in an isotropic sample. This arrangement ensures that only the grain orientation of the embedded grain influences the grain surface topography. The average surface height of the grain was then calculated to classify its behavior to be rising or sinking. Both experiment and simulation results show that the grains with the loading direction close to the < 001 > and < 111 > lattice orientations tend to sink. For the rest of the grain orientations, the loading direction orientation, and thus the Schmid or Taylor factor, cannot uniquely determine whether the grain rises or sinks. A parametric study revealed that a grain's average surface height is contributed by the plastic deformation of the most stressed slip systems along the direction normal to the surface.