Twin-induced grain boundary cracking in b.c.c. metals

Gilbert, A.; Hahn, G. T.; Reid, C.N.; Wilcox, B. A.

doi:10.1016/0001-6160(64)90230-5

Cited by 48 publications

(17 citation statements)

References 4 publications

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“…A brittle fracture occurs when the effective yield stress in the process zone at the notch tip exceeds the cleavage fracture stress (transgranular brittle fracture stress) or the grainboundary fracture stress (intergranular brittle fracture stress). These fracture stresses increase with a reduction in the average grain size, and this grain-size dependence is higher than the grain-size dependence of a yield stress [16]. According to the Griffith equation, the brittle fracture stress, r F , related to these weak sites is a function of the cohesive energy of fracture, c (in this case, the cohesive energy along the cleavage plane and the grain-boundary cohesive Table 1 Static mechanical properties at ambient temperature for TF(0°), TF(45°), and TF(90°) samples illustrated in Fig.…”

Section: Resultsmentioning

confidence: 91%

Effect of initial notch orientation on fracture toughness in fail-safe steel

Inoue

Kimura

2012

J Mater Sci

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A 0.4C-2Si-1Cr-1Mo steel bar with an ultrafine-elongated grain (UFEG) structures was produced by multi-pass warm caliber rolling. The test sample was machined from the rolled bar with 0°, 45°, and 90°rotation along the rolling direction, and a static three-point bending test was conducted at ambient temperature. The toughness anisotropy on the steel with UFEG structures were studied, including the crack propagation on the basis of the microstructural features. The strength and toughness decreased with an increase in the rotation angle along the rolling direction. The toughness decreased drastically, compared to the strength. The notch orientation dependence on toughness is due to differences in the spatial distribution of weak sites such as {100} cleavage planes and boundaries of elongated grains. For the toughness design in ultrafine-grained materials, it is essential to understand the spatial distribution of these weak sites as well as the grain size.

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Section: Resultsmentioning

confidence: 91%

Effect of initial notch orientation on fracture toughness in fail-safe steel

Inoue

Kimura

2012

J Mater Sci

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“…Previous research shows that critical fracture stress increases with reducing grain size, and when stress exceeds the critical fracture stress, cleavage fracture begins to occur. 17) The ferrite grains in the AR sample are elongated along the RD; therefore, they have a much larger size along the RD than they do along the transverse, resulting in much greater critical fracture stress for the transverse direction. This difference in critical fracture stress probably is the main cause for the aforementioned inclination in the AR sample.…”

Section: Resultsmentioning

confidence: 97%

Delaminating Crack Paths in Ultrafine, Elongated Ferritic Steel

2013

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“…In general, micron-order deformation twins in metallic materials are the origin of crack nucleation and cause early fracture, i.e., poor mechanical properties such as ductility, toughness, and fatigue; [37][38][39] however, the existence of nano-ordered twins is reported to contribute to the enhancement of not only strength and ductility [40] but also fracture toughness. [41] The existence of nanoordered twins was observed in the fracture toughness tested magnesium alloy with fine-grained structures, [42] and the fracture feature shows the ductile fracture associated with the dimple formation.…”

Section: Resultsmentioning

confidence: 99%

Deformation Mechanism in the Crack-Tip Region of Fine-Grained Magnesium Alloy

Somekawa

Inoue

Singh

et al. 2011

Metall Mater Trans A

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The deformation mechanism in the crack-tip region of a fine-grained Mg-2.4 at. pct Zn binary alloy was investigated by focused ion beam (FIB) and transmission electron microscopy (TEM) observation and finite element analysis (FEA) at the beginning of the fracture toughness test. The deformed microstructure observations showed the formation of subgrains instead of deformation twins in the fracture toughness tested sample, which was performed at a conventional crosshead speed of 1 mm/min. By preventing the formation of deformation twins at the beginning of the test, the crack tip of the fine-grained magnesium alloys became blunted, and thus, the alloys obtained high fracture toughness. Finite element results showed that the temperature increased 50 to 110 K, and the strain rate became two orders of magnitude higher; however, this temperature increment was not sufficient to form high-angle grain boundaries, i.e., a complete occurrence of dynamic recrystallization. On the other hand, the deformed microstructure observations in the sample, which was tested at a crosshead speed of 50 mm/min, showed the formation of nano-order {10-12} deformation twins and subgrains. The formation of deformation twins was caused, in part, by the severe strain from the operation of a high strain rate in the crack-tip region.

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Twin-induced grain boundary cracking in b.c.c. metals

Cited by 48 publications

References 4 publications

Effect of initial notch orientation on fracture toughness in fail-safe steel

Effect of initial notch orientation on fracture toughness in fail-safe steel

Delaminating Crack Paths in Ultrafine, Elongated Ferritic Steel

Deformation Mechanism in the Crack-Tip Region of Fine-Grained Magnesium Alloy

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