Effect of humidity on porosity, microstructure, and fatigue strength of A7N01S-T5 aluminum alloy welded joints in high-speed trains

Gou, Guoqing; Zhang, M.; Chen, H.; Chen, J.; Li, P.; Yang, Yuqiu

doi:10.1016/j.matdes.2015.06.177

Cited by 82 publications

(36 citation statements)

References 10 publications

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“…Fatigue test results were plotted in S‐N curves in terms of the nominal stress range (∆ σ ) against cycles to failure ( N f ). It is well known that pure aluminum and its alloys exhibit no obvious fatigue limit at 10 7 cycles or higher . The stress range corresponding to N f = 2 × 10 6 cycles was therefore set as the fatigue characteristic value or conditional fatigue strength according to the IIW.…”

Section: Methodsmentioning

confidence: 80%

Effect of microstructural features on the failure behavior of hybrid laser welded AA7020

Song

et al. 2018

Fatigue Fract Eng Mat Struct

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Detailed investigations of microstructural feature, mechanical property, fatigue strength, and damage mechanism were conducted on hybrid laser welded 7020‐T651 aluminum alloys used into high‐speed railway vehicles. The results show that the hybrid laser welding process can induce significant changes of microstructures and alloying elements, together with numerous gas pores. Such local modifications degrade the fatigue performance. The tensile strength of welded joints was approximately 74% with respect to the base metal, thus satisfying the design standard. The fatigue property was determined in the low and high cycle regimes. It was found that the fatigue strength of welded joints was fairly inferior to that of the base metal, but far higher than the IIW recommended value. Furthermore, welding defects were well believed to contribute to the shorter fatigue life. The small fatigue crack growth presented highly discontinuous and inhomogeneous due to microstructure and porosity. By contrast, the crack stable growth stage was less sensitive to microstructural features of hybrid welded joints.

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Section: Methodsmentioning

confidence: 80%

Effect of microstructural features on the failure behavior of hybrid laser welded AA7020

Song

et al. 2018

Fatigue Fract Eng Mat Struct

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“…Thus, an important decision related to its structural integrity must be made regarding weld defects and their effects on the strength of welded components. Only a limited number of studies have been reported in the literature on the effects of weld defects on the mechanical performances of heat-treatable aluminum alloy joints [8,[11][12][13]. Rudy and Rupert [11] and Gou et al [12] studied the effect of porosity on AA2XXX and AA7XXX welded joints, respectively.…”

Section: Introductionmentioning

confidence: 99%

“…Only a limited number of studies have been reported in the literature on the effects of weld defects on the mechanical performances of heat-treatable aluminum alloy joints [8,[11][12][13]. Rudy and Rupert [11] and Gou et al [12] studied the effect of porosity on AA2XXX and AA7XXX welded joints, respectively. Morton [13] showed a linear relationship between fracture strength and projected defect areas of TIG welded AA2XXX aluminum alloy.…”

Section: Introductionmentioning

confidence: 99%

Effects of Porosity, Heat Input and Post-Weld Heat Treatment on the Microstructure and Mechanical Properties of TIG Welded Joints of AA6082-T6

Wang

Xue

et al. 2017

Metals

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Abstract:Various heat input conditions and post-weld heat treatments were adopted to investigate the microstructure evolution and mechanical properties of tungsten inert gas (TIG) welded joints of AA6082-T6 with porosity defects. The results show that the fracture location is uncertain when an as-welded joint has porosities in the weld zone (WZ), and overaging in the heat-affected zone (HAZ) at the same time. When the fracture of the as-welded joint occurs in the HAZ, the total heat input has a linear relation with the tensile strength of the joint. An excess heat input induces the overgrowth of Mg 2 Si precipitates in HAZ and the coarsening of α-Al grains in WZ, resulting in a decrease in the microhardness of the corresponding areas. After artificial aging treatment, the tensile strength of the welded joint is increased by approximately 9-13% as compared to that of as-welded joint, and fracture also occurs in HAZ. In contrast, for solution treated and artificial aging treated joint, fracture occurs suddenly at the rising phase of the tensile curve due to porosity defects throughout the weld metal. Furthermore, the eutectic Si particles of WZ coarsen and spheroidize after solution treatment and artificial aging treatment, due to the diffusion of Si to the surface of the original Si phases when soaking at high temperature.

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“…The A7N01P‐T4 aluminum alloy belongs to Al‐Zn‐Mg alloy which has excellent aging characteristics and weldability. This alloy has been extensively used in underframes, corbels, section beams, end walls, and other important structures in high speed train due to its high strength to density ratio . However, this alloy is very susceptible to stress corrosion cracking (SCC) in aggressive environment such as chloride‐containing media and moist air .…”

Section: Introductionmentioning

confidence: 99%

Stress corrosion cracking and corrosion fatigue cracking behavior of A7N01P‐T4 aluminum alloy

Shen

Chen

et al. 2017

Materials & Corrosion

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A modified single edge notch tension (SENT) specimen exposed to saline environment was used to investigate the stress corrosion cracking and corrosion fatigue cracking behavior of A7N01P‐T4 aluminum alloy. The crack propagation rate was determined, the microstructure, crack growth path, and the fracture surfaces of specimens were examined by optical microscopy (OM) and scanning electron microscopy (SEM). The results showed that the stress corrosion cracking rate of A7N01P‐T4 alloy in 3.5% NaCl was three orders lower than that of corrosion fatigue crack propagation rate. Mg and Zn segregation at the grain boundaries increased the stress corrosion crack susceptibility. The grain orientation had a significant effect on the crack propagation performance, and the high angle grain boundaries were susceptible to cracking. Hydrogen embrittlement was the primary cause of stress corrosion crack and corrosion fatigue crack propagation.

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Effect of humidity on porosity, microstructure, and fatigue strength of A7N01S-T5 aluminum alloy welded joints in high-speed trains

Cited by 82 publications

References 10 publications

Effect of microstructural features on the failure behavior of hybrid laser welded AA7020

Effect of microstructural features on the failure behavior of hybrid laser welded AA7020

Effects of Porosity, Heat Input and Post-Weld Heat Treatment on the Microstructure and Mechanical Properties of TIG Welded Joints of AA6082-T6

Stress corrosion cracking and corrosion fatigue cracking behavior of A7N01P‐T4 aluminum alloy

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