The lattice strain ratio in characterizing the grain-to-grain interaction effect and its specific insight on the plastic deformation of polycrystalline materials

A single grain can contract or expand in the transverse direction when it is stretched. It becomes complex when the single grain is embedded in a stretched polycrystal, due to the grain neighborhood effect, which can outweigh the lateral contraction/expansion of that grain itself. Here, we performed numerical simulations to elucidate such grain-to-grain interaction effects on the lattice strain behavior. For individual grains in a polycrystal, pseudo Poisson’s ratio is defined. Ratios of Poisson’s ratio over pseudo Poisson’s ratio were employed to indicate the difference between the cases of the grain deformation with and without the constraint imposed from the neighboring grains. The high-stress spots and the sense of the stress components can be identified with a high possibility according to the proposed ratios. Most of the identified high-stress spots feature tensile stresses in three directions, while some of them feature the compressive stress in one transverse direction and a negative Poisson’s ratio. For the latter, a strong grain-to-grain interaction during the plastic stage of deformation is found. These grains induce the reversal of the lattice strain evolution curve for the measured <002>//TD, which is often found in the literature and in the data of neutron diffraction.