Quantitative metallography of precipitating and secondary phases after strengthening treatment of net shaped casting of Al-Zn-Mg-Cu (7000) alloys

Ghiaasiaan, Reza; Amirkhiz, Babak Shalchi; Shankar, Sumanth

doi:10.1016/j.msea.2017.05.047

Cited by 67 publications

(14 citation statements)

References 50 publications

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“…Artificial aging of the material brings the alloy into T4x temper. The positions of super lattice reflection of GP zones and Ș' precipitates are presented in a four folded pattern at the vicinity of 2/3 {220} positions [19]. The super lattice reflections were first observed in T4x condition.…”

Section: Microstructurementioning

confidence: 99%

“…Second area of concern with 7xxx aluminum usage comes from corrosion resistance which is preceived to be lower than 5xxx and 6xxx alloys. It has been reported in the literature [14][15][16][17][18][19] that 7xxx series aluminum alloys are susceptible to localized corrosion such as pitting, intergranular corrosion and stress corrosion cracking in aqueous solution containing particularly chloride ions. The corrosion behaviour of the 7xxx alloys was found to be strongly dependent on alloy composition and resulting microstructure, which is the evolution of material fabrication processes including thermo-mechanical history.…”

Section: Introductionmentioning

confidence: 99%

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A New Approach to Implement High Strength 7075 Aluminum for Automotive Application

2020

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Aluminum alloys offer high specific strength than advanced high strength steels, making them preferred candidates for automotive light weighting. Among them, AA7075 aluminum alloy offers significantly higher strength than 5xxx and 6xxx alloys and is considered an attractive candidate by automotive OEMs for structural applications such as door intrusion beams, B pillars etc. There are several challenges in implementing AA7075, such as long artificial aging time to reach peak strength, joining method and corrosion resistance. In this study, an artificial aging practice that significantly reduces aging time was explored and its influence on mechanical properties of AA7075 was investigated in comparison with conventional peak age practice. In addition, this practice offers a potential solution for joining through self-piercing riveting. Moreover, the effect of artificial aging on corrosion, specifically intergranular corrosion (IGC) and stress corrosion cracking (SCC) was evaluated. The results are discussed with in depth analysis and correlation with microstructure.

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Section: Microstructurementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

A New Approach to Implement High Strength 7075 Aluminum for Automotive Application

2020

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“…The precipitation-free zone (PFZ) with 40~70 nm width was observed near the grain boundary after holding for 10 h and the grain boundary was decorated with 50~80 nm precipitation phase. The specimen was over aged after 60 h holding, when the lath-type and rod-like η phases existed in the grain, which were incoherent with the matrix and decreased the hardness [23].…”

Section: Microstructure Investigationmentioning

confidence: 99%

Influence of Preaging Treatment on Bake-Hardening Response and Electrochemical Corrosion Behavior of High Strength Al-Zn-Mg-Cu-Zr Alloy

Liu

Wang

2019

Metals

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The influence of preaging (PA) treatments on the bake hardening (BH) response of a AlZnMgCuZr aluminum alloy which served as automotive body structures were studied in this paper. A novel two-step PA treatment was particularly designed and further employed. The mechanical properties of the alloy were tested in detail. The microstructure was characterized by optical microscope (OM), transmission electron microscopy (TEM) and 3D measuring laser microscope (3D–MLM). Meanwhile, the corrosion behavior was investigated by electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization. The results indicated that the PA treatment was beneficial for the improvement of BH response after baking at 180 °C immediately after the solution treatment and the micro-hardness reached the peak value (194 HV) after 10 h holding, which had a percentage improvement of 110.87% compared to the hardness under the solution condition. The PA treatments decreased natural aging (NA) adverse effects, while it had the lowest NA effect and optimal BH response under 120 °C/20 min. Such a novel two-step PA treatment was revealed further to decrease the NA effect and increase the BH response compared to the optimal PA treatment, in particular, the BH value could reach 168 MPa and was 21.7% higher than that of optimal PA + NA treatment. The optimal corrosion resistance has been shown up by the combined characterizations of potentiodynamic polarization curves, EIS Nyquist plots, and 3D–MLM images.

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“…Alloying, such as adding silicon (Si), copper (Cu), magnesium (Mg), zinc (Zn), manganese (Mn), and other elements, is the most important and effective method for improving the strength of Al. Solid-solution strengthening, second-phase strengthening, and precipitation strengthening are the primary mechanisms to strengthen Al alloys [5][6][7][8]. However, with the exception of adding Mg and Mn, alloying always leads to a significant decrease in the corrosion resistance of Al because of the appearance of cathodic secondary phases, which create microcorrosion cells with the Al matrix [9,10].…”

Section: Introductionmentioning

confidence: 99%

Effect of Ultrafine Grains on the Coating Reaction and Anticorrosion Performance of Anodized Pure Aluminum

et al. 2020

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This work analyzes the effects of ultrafine aluminum (Al) grains on the anodizing coating reaction and anticorrosion performance of anodized industrial pure Al. Equal-channel angular pressing (ECAP) was applied to cast pure Al continuously for 16 passes at room temperature, and its average grain size was dramatically refined to about 1.5 μm. The ultrafine-grain (UFG) pure Al was further anodized with a cast sample via a parallel anodizing circuit at a constant total input current. Benefited by the higher volume fraction of grain boundaries and higher internal energy of the UFG substrate, the anodizing process of the ECAP-processed pure Al was significantly accelerated, showing a more intense initial anodizing reaction, a faster initial coating thickening, and much earlier porous-layer formation compared to the cast sample. As the anodizing reaction continued, the newly formed thicker coating of the ECAP-coated sample significantly hindered the diffusion process, weakening the thermodynamic advantage and decreasing the anodizing current of the ECAP-processed sample. During the entire anodizing duration, the ECAP-processed pure Al experienced gradually decreased anodizing current, while the cast sample experienced increased anodizing current. Because of the more total reaction, the ECAP-coated sample always maintained a relatively thicker coating and better anticorrosion performance during the entire anodizing duration.

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Quantitative metallography of precipitating and secondary phases after strengthening treatment of net shaped casting of Al-Zn-Mg-Cu (7000) alloys

Cited by 67 publications

References 50 publications

A New Approach to Implement High Strength 7075 Aluminum for Automotive Application

A New Approach to Implement High Strength 7075 Aluminum for Automotive Application

Influence of Preaging Treatment on Bake-Hardening Response and Electrochemical Corrosion Behavior of High Strength Al-Zn-Mg-Cu-Zr Alloy

Effect of Ultrafine Grains on the Coating Reaction and Anticorrosion Performance of Anodized Pure Aluminum

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