A study of the dynamics of high temperature brittle intergranular fracture by acoustic emission

Hippsley, C. A.; Buttle, D.J.; Scruby, C. B.

doi:10.1016/0001-6160(88)90019-3

Cited by 21 publications

(7 citation statements)

References 11 publications

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“…164,165 The interest in stress induced brittle cracking was also underscored by the observation of low ductility intergranular fracture of low alloy steels. [166][167][168][169][170][171][172][173][174] Two alternate hypotheses 173,175 were proposed and analysed to theoretically describe the brittle mode of intergranular cracking. In one, called the 'pure drift' process, 173 it was proposed that although the cracking was in fact sulphur induced decohesion, it was caused by the diffusion of sulphur from the bulk to the grain boundaries ahead of the main crack tip.…”

Section: Stress-induced Segregation and Intergranular Decohesionmentioning

confidence: 99%

“…[166][167][168][169][170][171][172][173][174] Two alternate hypotheses 173,175 were proposed and analysed to theoretically describe the brittle mode of intergranular cracking. In one, called the 'pure drift' process, 173 it was proposed that although the cracking was in fact sulphur induced decohesion, it was caused by the diffusion of sulphur from the bulk to the grain boundaries ahead of the main crack tip. The sulphur was envisioned to be on its way to the free surface, under the influence of the stress field ahead of the crack, and the presence of the stress field made the grain boundaries perfect traps for the diffusion of sulphur.…”

Section: Stress-induced Segregation and Intergranular Decohesionmentioning

confidence: 99%

“…This hypothesis, aside from the absence of theoretical support for the proposed effect of stress on the binding energy of sulphur to the grain boundaries, was inconsistent with the scanning electron microscopy observations. 173 Also, the 'pure drift' process 164 relied on sulphur in substitutional solid solution in the bulk, which meant that a counter flow is required for the case of pure drift of a substitutional solute; the rate of drift is controlled by the bulk diffusion of the slower species, which is iron. This is about 1000 times smaller than that of sulphur at 550uC, and the introduction of this correction would drastically reduce the amount of sulphur build-up at the free surface or grain boundary, and would render it inconsistent with the experimental observations.…”

Section: Stress-induced Segregation and Intergranular Decohesionmentioning

confidence: 99%

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Unified mechanism of intergranular embrittlement based on non-equilibrium grain boundary segregation

Liu

Wang

et al. 2013

International Materials Reviews

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The review is aimed at presenting a unified approach in understanding the mechanism of nonequilibrium grain boundary segregation, which can satisfactorily describe the three types of intergranular embrittlement, namely, reverse temper embrittlement of steels, intergranular corrosion embrittlement of stainless steels and intermediate temperature embrittlement of metals and alloys. The review starts with a broad perspective of non-equilibrium grain boundary segregation, including thermally induced non-equilibrium grain boundary segregation and stress induced non-equilibrium grain-boundary segregation. Next, it focuses on the recent progress made in the non-equilibrium grain boundary segregation, including (1) critical time, (2) segregation peak temperature, (3) segregation peak temperature movement for thermally induced and stress induced non-equilibrium grain boundary segregation, and (4) the effect of temperature difference on thermally-induced non-equilibrium grain boundary segregation. Next, the attention is focused on the grain boundary coverage of elements and intergranular embrittlement phenomena. Three types of intergranular embrittlement is analysed in terms of (1) the ductility healing effect induced by the critical time, (2) embrittlement peak or ductility trough induced by the segregation peak temperature, (3) embrittlement peak or ductility trough movement induced by the segregation peak temperature movement and (4) widening and deepening of ductility trough induced by differences in temperature. These experimental phenomena concerning the three types of intergranular embrittlement are consistent with the models of thermally induced and stress induced non-equilibrium grain boundary segregations of impurities, instead of precipitation or equilibrium grain boundary segregation. Towards the end, we visit the subject of grain boundary segregation and associated embrittlement process from the viewpoint of fracture resistance and briefly discuss different perspectives that are of practical significance. List of symbolsA constant b the Burger's vector B Norton coefficient C b (t c ) grain boundary concentration at critical time C b(s50) equilibrium concentration of solute at the grain boundaries C g concentration of solute within the grains C v s~0 ð Þ equilibrium vacancy concentration at grain boundaries C v s~s ð Þ grain boundary vacancy concentration induced by the tensile stress D b the diffusivity D c diffusion coefficients for complexes under or in absence of applied tensile stress D i diffusion coefficients for solute atoms under or in absence of applied tensile stress E the elastic or Young's modulus -E the embrittlement sensitivity in K/at-% of solute at the grain boundary E b formation energy of vacancy solute atom complex International Materials Reviews 2013 VOL 58 NO 5263 E f vacancy formation energy E gb the elastic or Young's modulus of grain boundary region F v the formation energy of a vacancy in the boundary region H Z intergranular Auger peak to peak height of an element normalised with the ...

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Section: Stress-induced Segregation and Intergranular Decohesionmentioning

confidence: 99%

Section: Stress-induced Segregation and Intergranular Decohesionmentioning

confidence: 99%

Section: Stress-induced Segregation and Intergranular Decohesionmentioning

confidence: 99%

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Unified mechanism of intergranular embrittlement based on non-equilibrium grain boundary segregation

Liu

Wang

et al. 2013

International Materials Reviews

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“…Presumably, these losses are due in large part to reactions with the melting refractory. In addition, even small amounts of excess rare earths, e.g., b120 ppm, can cause complete loss of hot ductility by the formation of low melting eutectics such as Ni 5 Ce [94]. Numerous authors [94 to 98] report improvements in hot workability, creep rupture properties, and high temperature ductility, with Ce, La, Nd, and Y additions.…”

Section: Rare Earthsmentioning

confidence: 99%

Review of Trace Element Effects on High-Temperature Fracture of Fe- and Ni-Base Alloys

George¹,

Kennedy²,

Pope³

1998

phys. stat. sol. (a)

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Trace elements can have harmful or beneficial effects on elevated‐temperature mechanical properties. In iron and low‐alloy steels, S at high concentrations forms sulfides which are potent nucleation sites for intergranular creep cavities. As a result, ductility decreases and fracture becomes increasingly intergranular with increasing S concentration. Oxides and nitrides nucleate cavities only in the presence of segregated S; by themselves they are relatively benign. The harmful effects of S can be ameliorated by the addition of carbon and phosphorus. It is unclear whether C and P have beneficial effects of their own, or whether they act merely by counteracting the negative effects of sulfur. Carbides almost never nucleate cavities. In Ni‐base alloys, too, S is deleterious, and alloying with strong sulfide getters increases ductility and rupture life. Boron and P interact synergistically and increase stress rupture lives in some alloys but not in others. The detailed mechanism of this interaction is not well understood.

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“…To reach this goal we used diverse experimental methods like digital image correlation (DIC), acoustic emission recording and ultrasound wave propagation. The acoustic emission (AE) technique is widely used to study the fracture of paper [10][11][12][13] and other materials [14][15][16][17]. In parallel, wave propagation inside a heterogeneous sample offer a sensitive and non-invasive probe to follow the evolution of the elastic modulus [18][19].…”

Section: Introductionmentioning

confidence: 99%

Deformation, acoustic emission and ultrasound velocity during fatigue tests on paper

Miksic

Koivisto

Mykkänen

et al. 2010

EPJ Web of Conferences

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Abstract. We study the evolution of mechanical properties of paper samples during cyclic experiments. The issue is to look at the sample-to-sample variation, and we try to predict the number of loading cycles to failure. We used two concurrent methods to obtain the deformation: the strain was calculated from vertical displacement measured by laser interferometer sensor, as well as, computed by digital image correlation technique from pictures taken each 2s by a camera. Acoustic emission of fracture was also recorded, and an active ultrasonic wave method using piezoelectric transducers is used to follow the viscoelastic behaviour of each sample. We found that a sharp final increase of different variables like deformation, strain rate and fluctuations, are signs of an imminent rupture of the paper. Moreover looking at the evolution of these quantities during the first cycle only is already an indicator about the lifetime of the sample.

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A study of the dynamics of high temperature brittle intergranular fracture by acoustic emission

Cited by 21 publications

References 11 publications

Unified mechanism of intergranular embrittlement based on non-equilibrium grain boundary segregation

Unified mechanism of intergranular embrittlement based on non-equilibrium grain boundary segregation

Review of Trace Element Effects on High-Temperature Fracture of Fe- and Ni-Base Alloys

Deformation, acoustic emission and ultrasound velocity during fatigue tests on paper

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