Crack propagation along grain boundaries and twins in Mg and Mg–0.3 at.%Y alloy during in-situ straining in transmission electron microscope

Basha, Dudekula Althaf; Somekawa, Hidetoshi; Singh, Alok

doi:10.1016/j.scriptamat.2017.08.023

Cited by 49 publications

(4 citation statements)

References 29 publications

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“…A slightly different but related example of a critical need for intragranular stress measurements is the study of grain boundaries and the initiation, transfer, and impedance of plastic deformation. The behavior of plastic deformation at and across grain boundaries is related to defect accumulation, stress concentrations, and orientation relationships, also becoming preferential sites for damage and failure nucleation [42][43][44][45][46][47][48][49]. As a result, the direct experiment observation of the complex stress evolution at and across grain boundaries is of great interest to the material science community [18,[50][51][52][53][54][55][56].…”

Section: Introductionmentioning

confidence: 99%

Resolving intragranular stress fields in plastically deformed titanium using point-focused high-energy diffraction microscopy

Sharma

Kenesei

et al. 2023

Journal of Materials Research

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The response of a polycrystalline material to a mechanical load depends not only on the response of each individual grain, but also on the interaction with its neighbors. These interactions lead to local, intragranular stress concentrations that often dictate the initiation of plastic deformation and consequently the macroscopic stress–strain behavior. However, very few experimental studies have quantified intragranular stresses across bulk, three-dimensional volumes. In this work, a synchrotron X-ray diffraction technique called point-focused high-energy diffraction microscopy (pf-HEDM) is used to characterize intragranular deformation across a bulk, plastically deformed, polycrystalline titanium specimen. The results reveal the heterogenous stress distributions within individual grains and across grain boundaries, a stress concentration between a low and high Schmid factor grain pair, and a stress gradient near an extension twinning boundary. This work demonstrates the potential for the future use of pf-HEDM for understanding the local deformation associated with networks of grains and informing mesoscale models. Graphical abstract

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Section: Introductionmentioning

confidence: 99%

Resolving intragranular stress fields in plastically deformed titanium using point-focused high-energy diffraction microscopy

Sharma

Kenesei

et al. 2023

Journal of Materials Research

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“…Along with the dislocation accumulation in ferrite grains, stress in bainite matrix could hardly be released by the surrounded ferrite, which leads to the stress concentration at the interphase boundary of bainite and ferrite [36] and produces micro-cracks. The micro-cracks usually propagate along the high-angle grain boundaries [37], while macro-necking occurs, due to the interconnection of microcracks. Moreover, a number of micro-cracks have been simultaneously generated at the interphase boundary due to the higher large-angle grain boundary area of IC steel plate, as predicted in Figure 11a, which released the stress concentration and delayed the interconnection of micro-cracks.…”

Section: Discussionmentioning

confidence: 99%

Influence of Inter-Pass Cooling on Microstructural Evolution and Plastic Deformation of Heavy EH47 Plates

Wang

et al. 2019

Materials

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Herein, the influence of inter-pass cooling (IC) and conventional two-stage rolling (CTR), on microstructural evolution and plastic deformation behavior of ultra-heavy EH47 plates, is demonstrated. It is reported that the deformation amount and deformation rate, in every deformation pass during rough rolling, at 1/4- and 1/2-thickness of IC steel were higher than the CTR steel. The volume fraction of ferrite and acicular ferrite was 45% and 18%, at 1/4-thickness, and 35% and 50% at 1/2-thickness of IC steel, respectively, whereas the sum of both ferrite phases was smaller than 25% in the CTR steel. The austenite grain boundary area and high-angle grain boundary fraction in the IC steel were higher than the CTR steel. The high density of fine and shapeless pearlite has been observed in IC steel, whereas large-size carbides, with hexagonal structure, have been observed in CTR steel. Compared to the CTR steel, the density of precipitates was apparently lower in IC steel. Two kinds of Nb containing precipitates, such as (Ti, Nb)(C, N) and (Nb, Ti)C, were observed in the tested steels. Total ductility and uniform elongation of the IC steel were higher than the CTR steel. During the tensile process, the crack initiation energy and crack propagation energy of the IC steel were higher than the CTR steel. Moreover, the volume fraction of retained austenite (FCC) was reduced from 7.71% to 0.42% near the tensile fracture in IC steel at 1/4-thickness. In additon, the strain of synergetic plastic deformation of the IC steel was higher than the CTR steel. Meanwhile, compared to the CTR steel, the synergetic plastic deformation of the IC steel occurred at low stress after the yield point, which can be ascribed to the presence of fewer microcracks in the IC steel. Hence, a delayed fracture has been observed in the IC steel plate.

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“…The same fracture and propagation behaviors have been also observed in in-situ transmission electron microscopy (TEM) observation using a MgY alloy, which does not have a good property of toughness. 39) On the other hand, in the MgAl and MgZn alloys with higher fracture toughness than that of magnesium, the crack does not propagate along the grain boundaries, but rather into the matrix (grain interior). The fracture feature of these alloys shows ductile-like behavior.…”

Section: Fine-grained Magnesium Alloysmentioning

confidence: 99%

Effect of Alloying Elements on Fracture Toughness and Ductility in Magnesium Binary Alloys; A Review

Somekawa

2020

Mater. Trans.

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The development of magnesium alloys, which exhibit high strength and high ductility (fracture toughness), is critical for ensuring the safety and reliability in structural applications. It is well-known that grain refinement and/or alloying are impressive strategies to attain such properties in metallic materials. In the former case, grain boundaries of magnesium and its alloys have unique characteristics, e.g., sites for nonbasal dislocation activity and occurrence of partial grain boundary sliding. As a result, strength as well as ductility (fracture toughness) tend to increase and improve with grain refinement. In the latter case, 29 types of solid solution elements, which have a maximum solubility of more than 0.1 at%, can dissolve in magnesium. Several elements are generally added to magnesium simultaneously to achieve good mechanical properties via a synergistic effect. In industrial fields, ternary magnesium alloys such as MgAlZn and MgZnZr alloys, which have finegrained structures, have been widely used; however, there is no still clear and systematic understanding of the impact of various alloying elements on properties for magnesium. In this paper, we review recent studies on the effect of solid solution alloying elements on ductility (fracture toughness), with focusing on polycrystalline binary magnesium alloys. With regard to the toughness, the crack-propagation behavior and/or fracture behavior are quite sensitive to the alloying element, regardless of grain size. Twin boundaries in particular are recognized as harmful defects, because they act as crack-propagation sites. Nevertheless, changing the electric bonding behavior through alloying has the potential to increase the toughness. As for the ductility, the alloying elements also dramatically affect the room-temperature plastic deformation. In addition to the activation of the non-basal dislocation slip, grain boundary sliding also plays a notable role in enhancing the elongation-tofailure in tension.

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Crack propagation along grain boundaries and twins in Mg and Mg–0.3 at.%Y alloy during in-situ straining in transmission electron microscope

Cited by 49 publications

References 29 publications

Resolving intragranular stress fields in plastically deformed titanium using point-focused high-energy diffraction microscopy

Resolving intragranular stress fields in plastically deformed titanium using point-focused high-energy diffraction microscopy

Influence of Inter-Pass Cooling on Microstructural Evolution and Plastic Deformation of Heavy EH47 Plates

Effect of Alloying Elements on Fracture Toughness and Ductility in Magnesium Binary Alloys; A Review

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