Novel Insight of Dislocation Multiplication in Metallic Materials

Abstract

This paper demonstrates that high-angle grain boundaries tend to induce inhomogeneous intergranular stress distribution based on a bicrystal model. It further proposes a novel insight into dislocation multiplication in metals. Plastic deformation originates from crystal slip accompanied by dislocation generation. Crystal slip in polycrystalline materials is induced by a heterogeneous intergranular stress distribution, which arises from uneven deformation among grains. This deformation heterogeneity stems from the anisotropy of grain elastic moduli. Furthermore, greater differences in elastic moduli facilitate crystal slip, generating three-dimensional (3D) dislocations. Slip is favored in close-packed systems because their dislocations have smaller Burgers vectors, facilitating crystal slip and greater dislocation multiplication. For crystalline materials, greater dislocation half-width means longer slip length, accompanied by reduced yield strength and enhanced plastic capacity. Compared to body-centered cubic (BCC) crystals, face-centered cubic (FCC) metals possess more closely packed slip systems, larger dislocation half-widths, and smaller Burgers vectors. The more extensive slip in FCC crystals more effectively homogenizes the internal stress, thereby leading to their lower strength and higher plasticity compared to BCC crystals.