Deformation Banding and the Role of Transition Bands between α-Fibre Components on Recrystallization in Low Carbon Steels Studied by EBSD

2007 ◽  
Vol 539-543 ◽  
pp. 4173-4178 ◽  
Author(s):  
M. Díaz-Fuentes ◽  
Amaia Iza-Mendia ◽  
Isabel Gutiérrez

In extra-low carbon steels, the generation of specific nucleation sites in the deformed microstructure determines the formation of an optimum recrystallization texture. In particular, during the cold rolling of the steel sheets, transition bands are generated in order to accommodate the different deformation paths followed by the deformation bands (DB-s) within the grains. -fibre grains (ND-fibre grains) are, in general terms, more fragmented than -fibre grains (RD-fibre grains). Consequently, the higher orientation gradients and stored energy levels of the -fibre grains determine the ND-fibre annealing texture. Nevertheless, during recrystallization of the ELC steel, nucleation in different type of transition bands (TB-s) between α-fibre components has also been observed in the present work. From a previous crystallographic classification of transition bands done by the authors, the effect of the lattice curvature, either by gradual or sharp orientation gradients, is studied during early recrystallisation stages. Specifically, the crystallographic characteristics of recrystallized nuclei formed at transition bands generated between α-fibre components are analyzed using electron back-scatter diffraction (EBSD). This technique enables the orientation of deformation bands, the misorientation across them, the orientation of the new recrystallized grains and the misorientation of those grains with the adjacent matrix grains to be determined. Recrystallization of components different to α at the expense of α components has also been found.

2020 ◽  
Vol 58 (11) ◽  
pp. 752-758
Author(s):  
Seok-Woo Ko ◽  
Ji-Min Lee ◽  
Byoungchul Hwang

The effect of pre-strain on the hydrogen embrittlement of Nb-free and Nb-added low-carbon steels with ferrite-pearlite structure was investigated in this study. After the steels were electrochemically charged with hydrogen, slow-strain rate tensile (SSRT) tests were conducted on them to examine hydrogen embrittlement behavior. The SSRT test results revealed that the Nb-added steel had a lesser decrease of elongation and reduction of area than the Nb-free steel. The formation of NbC carbide and grain refinement caused by the Nb addition improved resistance to hydrogen embrittlement. The loss of elongation and the reduction of area after hydrogen charging occurs when pre-strain is increased. The pre-strain increases dislocation density and thus increases the amount of reversible hydrogen trap sites associated with hydrogen embrittlement. 10% pre-strained specimens exhibited a significant loss in elongation and reduction of area, regardless of Nb addition. Based on the results of electron back-scatter diffraction, fractographic, and silver decoration analyses for Nb-free and Nb-added steels, the hydrogen embrittlement mechanism in low-carbon steels with different amounts of pre-strain is discussed in terms of dislocation density and hydrogen distribution.


1976 ◽  
Vol 2 (2) ◽  
pp. 113-141 ◽  
Author(s):  
Hsun Hu

The effects of phosphorus on the annealing texture, plastic anisotropy, and mechanical properties of low-carbon steels containing 0.11 percent manganese have been studied. Both vacuum-melted and air-melted heats, with phsophorus additions up to 0.12 percent, were used. Results show that with a cold reduction of 80 percent, followed by annealing at temperatures in the range 710 to 820°C, the plastic strain ratios, rm and ∆r, as well as the strength of the steels were substantially improved by phosphorus. Annealing at the intercritical temperatures 780 and 820°C further improved the strain ratios. The strong tendency for phosphorus to segregate at the subgrain and grain boundaries is believed to have played an important role in controlling the formation of annealing textures in these steels.


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