Microstructural modeling of transgranular and intergranular fracture in crystalline materials with coincident site lattice grain-boundaries: Σ3 and Σ17b bicrystals

The microstructure and grain-boundary misorientation of X80 high-strength pipeline steel are analyzed using the scanning electron microscope, the electron backscatter diffraction, and the transmission electron microscope, and the effect of grain-boundary orientation on slip dislocation is investigated by constructing a grain-boundary dislocation model. The results show that the anisotropy of the mechanical properties of X80 pipeline steel is related not only to grain size and microstructure type but also to grain-boundary orientation, which the obstruction effect of the high-angle grain boundary on slip dislocation is significantly greater than that of the low-angle grain boundary. The larger the orientation difference is, the more disorderly the arrangement of atoms on both sides of grain boundary is, and the more difficult it is for dislocations to slip across grain boundary, so the strengthening effect is more remarkable. Also, when the grain-boundary misorientation is greater than 15 , the strengthening effect tends to stabilize due to the influence of the interfacial superposition.

Section: Test Results and Discussionmentioning

confidence: 99%

An Investigation on the Strengthening Mechanism Based on Grain‐Boundary Misorientation of High‐Strength Pipeline Steel

Duan

Pan

et al. 2019

“…Wu and Zikry [ 26 ] studied that the stress relief in crack tip during deformation was strongly affected by Σ3 (twin) boundaries, and Σ17b boundaries (86.63° <110>) blocked the growth of cleavage cracks. Although the glide plane of Fe–Si alloy may be {110}, {112} or {123} planes, the glide direction is always <111>.…”

Section: Discussionmentioning

confidence: 99%

Ordered Structure, Dislocation, and Grain Boundary Character Distribution and Their Effects on Warm Deformation in Soft‐Magnetic Fe–6.9Si–0.01B Alloy

Cai

Wang

Huang

et al. 2020

The ordered structure, dislocation, and grain boundary character distribution (GBCD) in warm‐rolled Fe–6.9Si–0.01B alloy are characterized, and their effects on plastic deformation are investigated. The study reveals that some {110} recrystallized grains preferentially formed at {111} shear bands as the main nucleation sites at lower rolling temperature, whereas more {111} recrystallized grains occur at 680 °C rolling temperature. The content and size of B2 ordered phases increase with increasing deformation temperatures, meanwhile majority of superdislocations are changed into single dislocations, relieving the stress through cross‐slip. The plastic deformability of Fe–6.9Si–0.01B alloy improves by increasing deformation temperature is attributed to a contribution combining decrease in order degree and recrystallization softening with optimization of GBCD.

“…Zikry et al found that CSL boundaries impeding dislocation transmission were prone to dislocation pile‐up and accumulation, and the stress relief in crack tip could be strongly influenced by the bicrystal with Σ3 CSL boundaries, in addition, the accelerated growth of cracks significantly decreased due to the effect of Σ17b (86.63°<110>) CSL boundaries. In comparison with the other CSL boundaries, Σ3 CSL boundaries are most beneficial to the plasticity required to prevent failure in service.…”

Section: Discussionmentioning

confidence: 99%

Effects of Coincident Site Lattice Grain Boundaries and Ordered Structures on Mechanical Properties of High Silicon Steel

Cai

Huang

2018

The coincident site lattice (CSL) grain boundaries and ordered structures of high silicon steel are investigated through different warm rolling reductions. The results reveal that the plastic deformation ability of Fe-6.9 wt%Si warmrolled sheet mainly depends on the total content of special P CSL boundaries and antiphase domain of ordered structures. With the increase of rolling reductions from 65% to 86%, the superdislocation glide behavior of warmrolled sheets is changed into the single dislocation glide, as well as the fragmentation behavior of ordered structures at different rolling reductions causes a decrease in the sizes of antiphase domains. While the sharp and homogeneous distribution of γ-orientation texture is beneficial to obtain a large fraction of P CSL boundaries that have great contribute to high resistance to the initiation and propagation of cracks. In the three-point bending tests, the values of fracture deflection improves from 3.5 mm to 12.1 mm, and the mixed fracture mode of inter-and trans-granular is transformed into quasi-cleavage fracture mode, which indicates the high rolling reduction is conducive to the improvement of plastic deformation ability.