Preferential Occurrence of Dynamic Recrystallization at Triple Junction in Copper Tricrystal

Abstract

Preferential occurrence of dynamic recrystallization (DRX) at triple junction (TJ) in pure copper tricrystals was investigated. DRX at TJ preferentially occurred at lower strain than the peak strain (about 2/3). All of the nucleated DRX grains at TJ were twins. Grain boundary sliding (GBS) was supposed to cause high stress concentration and deformation concentration near TJ because GBS was impeded at TJ. The twins were seemed to be nucleated behind the grain boundary migrating along the folding which was formed by impediment of GBS at TJ. These combined effects were supposed to cause the preferential DRX nucleation at TJ during high temperature deformation.

Strain Rate Effect on Dynamic Nucleation at Triple Junctions in a Copper Tricrystal

“…The DRX behavior at TJs in the present copper tricrystal, however, exhibited somewhat continuous DRX behavior, which is frequently observed in the metallic materials with high SFE. In spite of importance of migration of TJs along folding for twinning, 11,12) the TJs did not migrate in the present study. The occurrence of continuous DRX in copper was also reported by Belyakov et al 17) They attributed the fine grain evolution during severe plastic deformation to the distortion and recovery, which caused occurrence of continuous DRX.…”

“…11,12) These twins seemed to be formed during GBM. The DRX behavior at TJs in the present copper tricrystal, however, exhibited somewhat continuous DRX behavior, which is frequently observed in the metallic materials with high SFE.…”

“…The authors showed that DRX nucleation at TJ appeared at strains much lower than the peak strains. 11,12) Following their results, specimens were gas-queched for microstructural observations at much lower strains than the peak strains indicated by broken lines in Fig. 2.…”

“…Recently, Miura et al have reported from the experiments using copper tricrystals that triple junction (TJ) is one of the most preferential sites for DRX nucleation. 11,12) They explained that the observed preferential DRX nucleation at the TJ was caused by impediment of GBS, which formed deformation and stress concentration at the TJ. Such preferential DRX nucleation at TJ was revealed to generally occur even in polycrystalline copper.…”

“…Many studies with regarding to DRX mechanisms have been carried out. [1][2][3][4][5][6][7][8][9][10][11][12] It is revealed that DRX nucleation prefers places with high dislocation density and strain gradient. Humphreys and Hatherly have proposed the nucleation mechanism at particle/matrix interface by development of deformation zone.…”