Progress toward Understanding the Stress Corrosion Problem

Pugh, E. N.

doi:10.5006/1.3583022

Cited by 89 publications

(28 citation statements)

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“…[13][14][15][16][17][18][19][20][21][22][23][24][25] Typical PFZ widths, grain boundary precipitates and dislocation slip behaviors for various tempers are shown in Fig. 8-9.…”

Section: Microstructural Observationsmentioning

confidence: 99%

“…Several investigations have reported that the SCC mechanism involves anodic dissolution, [13][14][15] hydrogeninduced cracking (HIC), 5,13,[16][17][18] passive film rupture, 13,19) hydrogen embrittlement (HE), 14,15,20) magnesium segregation to grain boundaries [21][22][23] and a precipitate free zone (PFZ) along grain boundary. 24,25) However, the microstructural characteristics of Al-Zn-Mg high strength aluminum alloys are well known to have a strong influence not only on the mechanical properties but also on SCC susceptibility.…”

Section: Introductionmentioning

confidence: 99%

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Effects of Microstructure on the Mechanical Properties and Stress Corrosion Cracking of an Al-Zn-Mg-Sc-Zr Alloy by Various Temper Treatments

Wang

Hsu

et al. 2007

Mater. Trans.

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The high strength Al-Zn-Mg alloy used in the aerospace industry is strengthened by coherent G.P. zones and semicoherent 0 phase. However, this series of aluminum alloys are susceptible to stress corrosion cracking (SCC), particularly when aged to the peak-aged state of T6 temper. In this study, the effect of microstructure on mechanical properties and stress corrosion cracking of the alloy was investigated for alloys tempered to T6, RRA, Two-Step and T7 conditions by tensile test in air, SCC test and polarization test in a 3.5%NaCl solution. It is shown that the improvement in SCC resistance correlates very well with the size of matrix precipitates and grain boundary precipitates. T7 temper can produce larger sizes of both the matrix precipitates and grain boundary precipitates than that of T6, RRA and Two-step tempers, causing a decrease in the length and density of dislocation lines, which results in the decrease of stress concentration at grain boundary and greatly improving the SCC resistance. The addition of Sc and Zr to high strength Al-Zn-Mg alloys has been found to simultaneously improve the tensile strength and SCC resistance.

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“…[13][14][15][16][17][18][19][20][21][22][23][24][25] Typical PFZ widths, grain boundary precipitates and dislocation slip behaviors for various tempers are shown in Fig. 8-9.…”

Section: Microstructural Observationsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Effects of Microstructure on the Mechanical Properties and Stress Corrosion Cracking of an Al-Zn-Mg-Sc-Zr Alloy by Various Temper Treatments

Wang

Hsu

et al. 2007

Mater. Trans.

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“…Figure 14 shows Cr, Ni and P concentration profiles at different fluences. It is seen that the concentration gradients of these chemical elements across the grain boundary are unchanged at the unirradiated condition and 7:5Â10 19 and 1:1Â10 20 n/cm 2 , whereas they are significantly different at 6:2Â10 20 n/cm 2 , namely, Cr depletion and Ni enrichment occurred with a narrow peak of P segregation. Although a slight RIS-induced Cr depletion was detected, a high level of Cr concentration was still maintained at the grain boundaries.…”

Section: Tem Microstructural and Microchemical Examinationmentioning

confidence: 87%

Crack Initiation Mechanism in Non-ductile Cracking of Irradiated 304L Stainless Steels under BWR Water Environment

Onchi

Dohi

Navas

et al. 2006

J. Nucl. Sci. Technol.

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The deformation behavior and initiation mechanisms of intergranular (IG) and transgranular (TG) cracks in irradiated 304L stainless steel were studied by slow-strain-rate tensile tests in inert gas and simulated BWR water environments, followed by fractographic and microstructural examinations. Neutron irradiation was made in test reactors to fluences of up to 6:2Â10 20 n/cm 2 (E>1 MeV). Intergranular cracking occurred in water above a critical neutron fluence of around 1Â10 20 n/cm 2 , based on the results of the SSRT tests and SEM fractography. That critical fluence is mechanistically supported by irradiated, deformed microstructures exhibiting dislocation channeling at that fluence, while radiation-induced Cr depletion at the grain boundaries was minor. Transgranular cracking of the irradiated material occurred in water below the critical fluence, initiating in the non-uniformly strained surface region of the test bar in the later stages of plastic deformation. The initiation of TG cracking is hypothesized to be related to a high density of deformation twins. Intergranular cracking is proposed to have initiated where localized slip bands terminated at grain boundaries, while TG cracking is inferred to have initiated at deformation twin boundaries. High stress and strain concentrations at grain/twin boundaries would be the common cause of non-ductile crack initiation.

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“…Several investigations have reported that the SCC mechanism involves anodic dissolution, hydrogen-induced cracking, passive film rupture, hydrogen embrittlement, magnesium segregation to the grain boundaries and a precipitate-free zone (PFZ) along the grain boundary. [6][7][8][9][10] However, the microstructural characteristics of Al-Zn-Mg-Cu high strength aluminum alloys are well known to have a strong influence not only on the mechanical properties but also on the SCC susceptibility. Larger grain-boundary precipitates can trap more atomic hydrogen to nucleate hydrogen bubbles, thereby decreasing the hydrogen concentration at grain boundaries below a critical value is considered to prevent intergranular SCC fracture.…”

Section: Introductionmentioning

confidence: 99%

Development of a heat treatment for increasing the mechanical properties and stress corrosion resistance of 7000 Al alloys

Shakouri¹,

Esmailian²,

Shabestari³

2017

Mater. Tehnol.

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A retrogression and re-ageing (RRA) treatment is a three-step heat treatment that can improve both the mechanical strength and the corrosion resistance in aluminum alloys. In this work, the mechanical and stress corrosion properties under various ageing treatment conditions were investigated in an Al-8.5Zn-2.1Mg-2Cu-0.2Ag (w/%) alloy. The treatments were the T6 conventional method followed by a retrogression and re-ageing (RRA) treatment. Tensile test, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS) and differential scanning calorimetry (DSC) were used to investigate the mechanical and stress corrosion cracking (SCC) properties. The results showed that both, the strength and the corrosion resistance criteria (SCR), which is defined as the ratio between the remaining strength percent in stressed and un-stressed conditions, improve after the RRA treatment. The tensile strength and SCR criteria for the T6 heat treatment were 547 MPa and 71 % initially and then increased to 612 MPa and 95 % for the RRA treatment, respectively. Moreover, the EDS results showed that in grain-boundary precipitates the Cu concentration is much higher for the RRA in comparison with the T6 treatment, but it is lower for the matrix precipitates in the RRA treatment. Keywords: aluminium alloys, stress corrosion resistance, precipitation, retrogression and re-ageing Obdelava z retrogresijo in ponovno o`ivitvijo (angl. RRA) je tristopenjska toplotna obdelava, s katero lahko izbolj{amo tako mehansko trdnost kot odpornosti proti koroziji pri aluminijevih zlitinah. V pri~ujo~em delu so bile raziskovane mehanske lastnosti in lastnosti odpornosti proti koroziji pri zlitini Al-8.5Zn-2.1Mg-2Cu-0.2Ag (w/%) pod razli~nimi pogoji obdelave staranja. Izvedeni so bili testi po konvencionalni T6 metodi, z upo{tevanjem RRA obdelave. Natezni preiskus, vrsti~na elektronska mikroskopija (SEM), energijsko disperzijska rentgenska spektroskopija (EDS) in DSC-testiranja so bili izvedeni, da bi raziskali mehanske in napetostno-korozijske lomne lastnosti (angl. SCC). Rezultati so pokazali, da se oba kriterija tako trdnost kot odpornost proti koroziji, ki definirata razmerje med procentom zaostale trdnosti pri napetostnih in nenapetostnih pogojih, po RRA-obdelavi izbolj{ata. Klju~ne besede: aluminijeve zlitine, odpornost proti koroziji, oborine, retrogresija in ponovno staranje

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Progress toward Understanding the Stress Corrosion Problem

Cited by 89 publications

References 0 publications

Effects of Microstructure on the Mechanical Properties and Stress Corrosion Cracking of an Al-Zn-Mg-Sc-Zr Alloy by Various Temper Treatments

Effects of Microstructure on the Mechanical Properties and Stress Corrosion Cracking of an Al-Zn-Mg-Sc-Zr Alloy by Various Temper Treatments

Crack Initiation Mechanism in Non-ductile Cracking of Irradiated 304L Stainless Steels under BWR Water Environment

Development of a heat treatment for increasing the mechanical properties and stress corrosion resistance of 7000 Al alloys

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