Evaluation of Dislocation Density for 1100 Aluminum with Different Grain Size during Tensile Deformation by Using <i>In-Situ</i> X-ray Diffraction Technique

Abstract

Ultra-fine-grained (UFG) aluminum with a grain size of 260nm was fabricated by annealing a severely plastically deformed A1100 alloy. The resulting UFG aluminum exhibited a 0.2% proof stress (·0.2) that was four times larger than that predicted by the conventional Hall-Petch relation. In this study, the UFG aluminum, the fine-grained aluminum with a grain size of 960nm and the coarse-grained aluminum with a grain size of 4.47µm were prepared. The change in the dislocation density, μ was investigated during tensile deformation using in-situ X-ray diffraction measurements at SPring-8. It was found that as the strain increased, the μ changed in four distinct stages. The first stage was characterized by elastic deformation, and little change in the μ occurred. For the coarse-grained aluminum, this stage was almost absent. In the second stage, the μ rapidly increased until the stress reaches ·II in which the plastic deformation begins to occur at a constant strain rate. In the third stage, only a moderate change in the μ occurred. Finally, in the fourth stage, the μ rapidly decreased as the test pieces underwent fracture. Additionally, it was found that the ·0.2-·I was followed by the conventional Hall-Petch relation in all grain size range. [doi:10.2320/matertrans.L-M2015803]