Papers by Keyword: Strain Induced Boundary Migration

Abstract: The 7000 series aluminum alloys suffer from intergranular fracture (IGF) that limits the use of the alloys, although they have highest strength among aluminum alloys. The types of IGF can be classified into two categories: (i) with smooth fracture surface showing practically no plastic deformation that takes place in hydrogen embrittlement and stress corrosion cracking, and (ii) with shallow and fine dimples on the fracture surface showing localized plastic deformation inside precipitate free zones. In this study, attempts have been made to suppress the IGF of both types by (a) controlling precipitate microstructure on grain boundaries by quench control and (b) controlling grain boundary morphology by strain induced boundary migration. The IGF of type (i) (hydrogen embrittlement) was successfully suppressed both by the two controlling processes.

Abstract: In order to get optimal grain boundary character distribution (GBCD) and grain boundary properties, thermomechanical processing (TMP) is usually adopted in grain boundary engineering. However, the mechanism behind the TMP treatments and GBCD optimization is still unclear. The present study has conducted a series experiments involving low-strain TMPs to study the relationship between TMP parameters and the behind microstructural evolution. The experimental results indicate that in the scope of low-strain TMP, strain induced boundary migration (SIBM) is the most effective process for GBCD optimization. Besides, SIBM and grain growth would gradually transfer to recrystallization with the increase of pre-deformation level and annealing temperature. Further quasi in-situ EBSD results infer that SBIM is activated locally in some region with high stored energy, and further gradual initiation of SIBM from one region to another contributes to the gradual increase of special boundaries with annealing time.