Effects of lead on the sustained-load cracking of AlMgSi at ambient temperatures

Lewandowski, John J.; Kohler, V.; Holroyd, N.J.H.

doi:10.1016/0025-5416(87)90552-0

Cited by 17 publications

(3 citation statements)

References 7 publications

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“…[3,81,83,84] (b) Although GBS at sufficiently low strain rates is observed in vacuum, [3,81,83,84] the initiation of intergranular SLC will not readily occur in dry air, [45] but requires the presence of a suitable local environment capable of promoting AD of freshly exposed surfaces to provide a local source of atomic hydrogen. (c) Overaging high-copper-containing alloys markedly reduces GBS, whereas it is less effective on lowcopper-containing alloys.…”

Section: Mechanistic Implicationsmentioning

confidence: 99%

Crack Propagation During Sustained-Load Cracking of Al-Zn-Mg-Cu Aluminum Alloys Exposed to Moist Air or Distilled Water

Holroyd¹,

Scamans

2011

Metall Mater Trans A

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Intergranular sustained-load cracking of Al-Zn-Mg-Cu (AA7xxx series) aluminum alloys exposed to moist air or distilled water at temperatures in the range 283 K to 353 K (10°C to 80°C) has been reviewed in detail, paying particular attention to local processes occurring in the crack-tip region during crack propagation. Distinct crack-arrest markings formed on intergranular fracture faces generated under fixed-displacement loading conditions are not generated under monotonic rising-load conditions, but can form under cyclic-loading conditions if loading frequencies are sufficiently low. The observed crack-arrest markings are insensitive to applied stress intensity factor, alloy copper content and temper, but are temperature sensitive, increasing from~150 nm at room temperature to~400 nm at 313 K (40°C). A re-evaluation of published data reveals the apparent activation energy, E a for crack propagation in Al-Zn-Mg(-Cu) alloys is consistently~35 kJ/mol for temperatures above~313 K (40°C), independent of copper content or the applied stress intensity factor, unless the alloy contains a significant volume fraction of S-phase, Al 2 CuMg where E a is~80 kJ/mol. For temperatures below~313 K (40°C) E a is independent of copper content for stress intensity factors below~14 MNm À3/2 , with a value~80 kJ/mol but is sensitive to copper content for stress intensity factors abovẽ 14 MNm À3/2 , with E a , ranging from~35 kJ/mol for copper-free alloys to~80 kJ/mol for alloys containing 1.5 pct Cu. The apparent activation energy for intergranular sustained-load crack initiation is consistently~110 kJ/mol for both notched and un-notched samples. Mechanistic implications are discussed and processes controlling crack growth, as a function of temperature, alloy copper content, and loading conditions are proposed that are consistent with the calculated apparent activation energies and known characteristics of intergranular sustained-load cracking. It is suggested, depending on the circumstances, that intergranular crack propagation in humid air and distilled water can be enhanced by the generation of aluminum hydride, AlH 3, ahead of a propagating crack and/or its decomposition after formation within the confines of the nanoscale volumes available after increments of crack growth, defined by the crack arrest markings on intergranular fracture surfaces.

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Section: Mechanistic Implicationsmentioning

confidence: 99%

Crack Propagation During Sustained-Load Cracking of Al-Zn-Mg-Cu Aluminum Alloys Exposed to Moist Air or Distilled Water

Holroyd¹,

Scamans

2011

Metall Mater Trans A

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“…Although this mechanism has been demonstrated by microscopic observations of fracture surfaces, which clearly show striations [8,10], other models predict a more continuous form of fracture [11]. Small amounts of lead are shown to cause intergranular fracture in aluminum alloys when tested under very low strain rates (10 −6 s −1 ) or under sustained load conditions at near ambient temperatures [12,13].…”

Section: Introductionmentioning

confidence: 97%

Lead induced intergranular fracture in aluminum alloy AA6262

Wouters

Hosson

2003

Materials Science and Engineering: A

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“…[8,40] All these factors can give rise to statistical variations that are beyond the scope of the current article. However, the measured scatter may also be associated with a range of other reasons.…”

Section: Statistical Distributionsmentioning

confidence: 99%

A Statistical Approach to the Prediction of Brittle Fracture in Heat-Affected Zones of A707 Steel Welds

Zhou

Soboyejo

2004

Materials and Manufacturing Processes

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This article presents a statistical approach to the prediction of the variations in fracture toughness of the heat-affected zones in A707 steel welds. Fractographic analyses were first used to determine the inclusion size distributions from the ductile fracture regions that precede the onset of cleavage fracture. The inclusion size distributions were shown to be well characterized by the three-parameter Weibull distribution. Based on the inclusion size distribution, a modified version of the model by Lin, Evans, and Ritchie was used to estimate the statistical variability of the crack-tip opening displacement (fracture toughness). The modification involves the use of a polynomial function in the determination of the dimensionless stress parameter, ij ðn, Þ, in the Hutchinson-Rice-Rasengren (HRR) field solution. This enables a fully analytical solution to be obtained for the critical driving forces associated with specified failure/survival probabilities under elastic-plastic fracture conditions. The comparison showed that the modified model prediction was in good agreement with measured crack-tip opening displacement (fracture toughness) data. Finally, the implications of the results are discussed for the probabilistic design of damage tolerant structures in which cleavage fracture can occur, following an initial stage of ductile tearing by microvoid coalescence.

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Effects of lead on the sustained-load cracking of AlMgSi at ambient temperatures

Cited by 17 publications

References 7 publications

Crack Propagation During Sustained-Load Cracking of Al-Zn-Mg-Cu Aluminum Alloys Exposed to Moist Air or Distilled Water

Crack Propagation During Sustained-Load Cracking of Al-Zn-Mg-Cu Aluminum Alloys Exposed to Moist Air or Distilled Water

Lead induced intergranular fracture in aluminum alloy AA6262

A Statistical Approach to the Prediction of Brittle Fracture in Heat-Affected Zones of A707 Steel Welds

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