“…In the case of small strains, the annealing causes the dislocations to rearrange into local bands, which may develop into a subgrain structure. In heavily deformed metals, on the other hand, an additional softening before the onset of recrystallisation will take place which appears to be controlled by subgrain growth [33]. Figure 2 Microstructures of as-received, deformed and heat-treated Armco iron.…”
The goal of this study is to obtain a deeper insight in the relation between hydrogen diffusion and hydrogen traps present in Armco pure iron. Cold deformation was applied to this material, which initially contained a limited amount of traps. The cold deformation was applied to increase the dislocation density and modify grain boundary characteristics. In this way, the hydrogen diffusivity decreased as the hydrogen trapping ability of the microstructure increased. A subsequent heat treatment allowed changing the density of microstructural defects again and consequently increased the hydrogen diffusion coefficient. In addition, studying blister formation showed that a higher degree of deformation caused more surface blisters, while recovery lowered the number of blisters. Electron backscatter diffraction characterisation provided the necessary input on the microstructural features and their evolution. Analysis of these samples allowed evaluating the correlation between hydrogen diffusion, blister formation and microstructural defects. This paper is part of a thematic issue on Hydrogen in Metallic Alloys
“…In the case of small strains, the annealing causes the dislocations to rearrange into local bands, which may develop into a subgrain structure. In heavily deformed metals, on the other hand, an additional softening before the onset of recrystallisation will take place which appears to be controlled by subgrain growth [33]. Figure 2 Microstructures of as-received, deformed and heat-treated Armco iron.…”
The goal of this study is to obtain a deeper insight in the relation between hydrogen diffusion and hydrogen traps present in Armco pure iron. Cold deformation was applied to this material, which initially contained a limited amount of traps. The cold deformation was applied to increase the dislocation density and modify grain boundary characteristics. In this way, the hydrogen diffusivity decreased as the hydrogen trapping ability of the microstructure increased. A subsequent heat treatment allowed changing the density of microstructural defects again and consequently increased the hydrogen diffusion coefficient. In addition, studying blister formation showed that a higher degree of deformation caused more surface blisters, while recovery lowered the number of blisters. Electron backscatter diffraction characterisation provided the necessary input on the microstructural features and their evolution. Analysis of these samples allowed evaluating the correlation between hydrogen diffusion, blister formation and microstructural defects. This paper is part of a thematic issue on Hydrogen in Metallic Alloys
“…Evidence shows the edge dislocations, which form the Cottrell atmosphere, are not eliminated until 350 °C [ 48 ]. For commercial iron, when the tempering temperature is higher than 400 °C, an apparent dislocation recovery is detected by positron annihilation spectroscopy [ 49 ]. Even annealed at 227 °C for 10 h, the decrease in steel dislocation density will not be noticeable [ 50 ].…”
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