Stress corrosion cracking (SCC) of aluminium alloys

Kannan, M. Bobby; Srinivasan, P. Bala; Raja, V.S.

doi:10.1533/9780857093769.3.307

Cited by 20 publications

(8 citation statements)

References 76 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…On the other hand, the SCC performance of 7xxx series aluminum alloy plates can be improved by microalloying techniques. For instance, Bobby Kannan [6] and our previous work [20] showed that the SCC resistance of Al-Zn-Mg-Cu-Zr or Al-Zn-Mg alloys can be improved by adding 0.25 wt.% scandium, even in the peak aged state. Wang [21] indicated that Al-Zn-Mg-Cu-Zr alloys with Cr and Pr exhibited higher resistance to SCC than those without Pr-or Zr-containing dispersoids.…”

Section: Instructionmentioning

confidence: 99%

“…Al-Zn-Mg alloys, due to their high-strength-weight, are applied widely in aerospace structural components and for highly stressed parts in automobiles and high-speed trains for fuel saving [1][2][3]. When airplanes or trains are in service in humid environments such as those present in marine, industry or rural atmospheres, 7xxx series aluminum alloys used as air-frame structures and car body members are exposed to mechanical loading, and thus, suffer from stress corrosion cracking (SCC) [2,[4][5][6]. Adding high contents of alloying elements, such as Zn and Mg, is the main method to strengthen heat-treatable, ageing-hardenable aluminum alloys [7,8].…”

Section: Instructionmentioning

confidence: 99%

“…Currently, the measures taken to improve the SCC resistance of 7xxx series aluminum alloys are mainly based on optimizing quenching and aging heat treatment processes [2,5], or adding rare earth elements to modify the grain boundaries [13,14]. T7 over-aging treatment [2,4,6], retrogression and re-aging (RRA) [15], dual-retrogression and re-aging (DRRA) [16] and step-quench and aging heat treatment (SQA) [6,16] have been reported to be effective in enhancing the SCC resistance of Al-Zn-Mg(-Cu) alloys. However, overaging to a T7 state would lead a loss of about 10-15% in strength, and due to the demand of a short retrogression or step-quench time, RRA, DRRA and SQA are not suitable for the large-scale fabrication using 7xxx series aluminum alloys with high quenching sensitivities.…”

Section: Instructionmentioning

confidence: 99%

See 2 more Smart Citations

Nanostructure Characteristics of Al3Sc1−xZrx Nanoparticles and Their Effects on Mechanical Property and SCC Behavior of Al–Zn–Mg Alloys

2020

View full text Add to dashboard Cite

The Nanostructure characteristics of Al3Sc1−xZrx nanoparticles and their effects on the mechanical properties and stress corrosion cracking (SCC) behavior of Al–Zn–Mg alloys were investigated by 3D atom probe analyses, high-angle annular-dark-field scanning transmission electron microscopy methods, electron back scattered diffraction techniques, electrochemical measurements, slow strain rate tests and quantitative calculations. The results show that adding small amounts of scandium (0.10 percent by weight) and zirconium into Al–Zn–Mg extrusion bars can precipitate Al3Sc1−xZrx nanoparticles with a number density of (7.80 ± 3.83) × 1021 per cubic meter. Those particles, with a low lattice misfit with matrix (1.14 ± 0.03 percent) and stable core-shell L12-nanostructure in aged Al–Zn–Mg alloys, can increase the yield strength by 161 ± 7 MPa via strong Orowan strengthening (the theoretical calculated value is 159 MPa) and weak Hall-Petch strengthening (the theoretical calculated value is 6 MPa). Moreover, Al3Sc1−xZrx nanoparticles can change the fracture mechanism of alloys in 3.5% NaCl solution from intergranular cracks to transgranular failure, and decrease the proportion of high-angle grain boundaries from 87% to 31%, thus reducing the microchemistry differences around the grain boundaries and anodic dissolution kinetics, and improving intergranular SCC resistance and ductility. This study offers a new approach to the simultaneous improvement in mechanical property and corrosion performance of high strength alloys.

show abstract

Section: Instructionmentioning

confidence: 99%

Section: Instructionmentioning

confidence: 99%

Section: Instructionmentioning

confidence: 99%

See 1 more Smart Citation

Nanostructure Characteristics of Al3Sc1−xZrx Nanoparticles and Their Effects on Mechanical Property and SCC Behavior of Al–Zn–Mg Alloys

2020

View full text Add to dashboard Cite

show abstract

“…Bobby et al [37][38][39][40][41][42][43] carried out an extensive work on understanding the electrochemical and EAC behavior of 7010 Al alloy by heat treatment procedures and alloying. However, EAC in Al alloys has been a serious concern for aircraft industries for decades.…”

Section: Aluminium Alloysmentioning

confidence: 99%

“…The multi-step aging treatment is advantageous over RRA treatment in that the former can be applied to even thick plates, while the latter is restricted to thin sheets because of the short retrogression treatment at elevated temperature. Bobby et al [39] further showed that a higher ductility of peak aged and over aged alloys could be achieved through multi-step aging than that was reported by Puiggali et al through conventional aging [53], Table 1 SSRT data of 7010 Al-alloys in peak aged and over aged conditions tested in air and 3.5% NaCl solution at 10' 6 /s strain rate [37] Temper % Elongation to Detailed microstructure and fractured surface analysis of heat treated 7010 Al alloy were carried out by Bobby et al [37,39,40,42] to correlate the microstructure to the failure mechanism(s). In air, the peak aged alloy exhibited 10% C f (elongation to fracture) and 10%RA and 561 MPa UTS.…”

Section: Role Of Heat Treatmentmentioning

confidence: 99%

Environmentally-Assisted Cracking of Engineering Materials - An Insight

Kannan¹,

Raja²

2009

Corrosion Reviews

View full text Add to dashboard Cite

This paper reviews the environmentally-assisted cracking studies of some of the key engineering materials i.e. austenitic stainless steels, aluminium alloys and magnesium alloys. Some of the salient work carried out by the research laboratories and institutions in India and other countries, in this critical research area, are brought out in this paper. Environmentally-AssistedCracking of Engineering Materials known as EAC. Stresses arise in practice from applied load or from residual stress due to welding or inhomogeneous plastic deformation.The literature on EAC of engineering materials is vast, and there are many useful textbooks and conference proceedings [1][2][3][4][5]. Understanding the EAC mechanism(s) in metals has been a subject of interest for decades.Basically, the EAC can be broadly classified into two groups: (i) anodic dissolution assisted cracking and (ii) hydrogen-induced cracking. Many models have been put forward, in literature, to explain the EAC mechanism(s). The slip-dissolution model is one of them explaining the crack growth occurring by extremely localized dissolution of the metal. This model states that the crack is protected by a film, usually an oxide, which is fractured as a result of plastic strain in the metal at the crack tip. The crack growth proceeds by a cyclic process of film-rupture, dissolution and filmrepair. This model has been mainly cited to explain the intergranular cracking of femtic steels in passivating environments such as carbonate-bicarbonate solutions as well as sensitised stainless steels in a variety of environments.Later, a film-induced cleavage model was proposed to explain the brittle failure of alpha-brass due to dezincification in ammonia solution. Hydrogeninduced cracking or hydrogen embrittlement in metallic materials is also widely accepted as a mechanism of failure in recent years. Hydrogen discharge and absorption are favoured when there is acidification of the local environment by cation hydrolysis, especially if this acidification damages or destroys a passive film in the crack. Once hydrogen is absorbed in the metal, it can promote cleavage, intergranular separation, or a highly localized plastic fracture. In hydride-forming metals such as Mg and Ti, formation of brittle hydrides can be part of the fracture mechanism.The research organisations and institutions in India have contributed significantly to the understanding of EAC behaviour of engineering materials. Some of the key research works carried out in this research area by

show abstract