Study of retrogression response in naturally and multi-step aged Al-Mg-Si automotive sheets

Gao, Guanjun; Li, Y.; Wang, Z.D.; Misra, R.D.K.; Li, J.D.; Xu, Guojun

doi:10.1016/j.jallcom.2018.04.198

Cited by 19 publications

(10 citation statements)

References 28 publications

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“…Precipitation hardening of an Al–Mg–Si alloy is an ideal choice for the automobile industry because of its high strength-to-weight ratio, good formability, excellent corrosion resistance, and low cost [1,2,3]. Increased strength in alloys is acquired by paint-bake hardening after the solution is heat-treated at 560 °C and rapidly quenched to room temperature (RT) [4,5,6]. During paint-bake hardening, a large number of transition phases are formed in the matrix, resulting in a strengthening effect.…”

Section: Introductionmentioning

confidence: 99%

Effects of the Mg/Si Ratio on Microstructure, Mechanical Properties, and Precipitation Behavior of Al–Mg–Si–1.0 wt %-Zn Alloys

Gao

Wang

et al. 2018

Materials

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Aluminum alloys are widely used as first-choice materials for lightweight automotive applications. It is important that an alloy have a balance between strength and formability. In this study, the alloys were melted, cast, hot rolled, and cold rolled into 1 mm-thick sheets. The microstructure, mechanical properties, and precipitation behavior of Al–Mg–Si–1.0 wt %-Zn alloys with Mg/Si ratios of 0.5, 1, and 2 after solution treatment were studied using optical and electron microscopy, a tensile test, the Vickers hardness test, and differential scanning calorimetry. The results showed that a high density and number of Al–Fe–Si particles were observed in the matrix, thus causing the formation of more homogeneous and smaller recrystallized grains after treatment with the solution. In addition, a higher volume fraction of cubeND and P-types texture components formed during solution treatment. Also, a high r value and excellent deep drawability were achieved in the medium-Mg/Si-ratio alloy. The formation of denser strengthening precipitates led to a better paint-bake hardening effect in comparison with the other two alloys. Furthermore, the precipitation kinetics were enhanced by the addition of Si, and the addition of Zn did not alter the precipitation sequence of the Al–Mg–Si alloy. The dual-phase strengthening effect was not achieved in the studied alloys during paint-bake treatment at 175 °C.

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Section: Introductionmentioning

confidence: 99%

Effects of the Mg/Si Ratio on Microstructure, Mechanical Properties, and Precipitation Behavior of Al–Mg–Si–1.0 wt %-Zn Alloys

Gao

Wang

et al. 2018

Materials

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“…The observed decrease in hardness of the as-quenched and natural aged sample upon the paint-bake is caused by dissolution of clusters. This oft-reported behavior occurs at the beginning of artificial aging and is known as reversion [5,19,20]. Additionally, in our case, the paint-bake process can be seen as a shortened artificial aging treatment.…”

Section: Discussionmentioning

confidence: 80%

“…The results from paint-bake simulation (Figure 12) show no new increases in hardness increments, which have been found upon a spike after natural aging [20]. Samples without Sn (Figure 12a) show no increased responses for PA3.…”

Section: Discussionmentioning

confidence: 99%

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Effect of Thermal Treatments on Sn-Alloyed Al-Mg-Si Alloys

et al. 2019

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Sn-alloying, by deploying comparatively high vacancy binding energy, mitigates the undesired natural aging behavior of 6xxx-alloys. Targeted selection of pre-aging parameters can have a positive influence on natural aging and paint-bake performance. In this study, we aimed to combine the two approaches of Sn-alloying and pre-aging. Our results indicate that alloys modified with 100 at.-ppm Sn require altered heat treatment. In terms of solution aging and quenching, we show that the cooling rate needed depends on the types of alloy. The rate must be adapted, according to the number of intermetallic particles, to guarantee a sufficiently high level of Sn atoms in solid solution. The rather high number of intermetallic phases in alloy EN-AW-6061 means that it requires fast quenching, while the comparatively low number of precipitate-forming elements in alloy EN-AW-6016 makes it less sensitive to quenching variations. We also show that Sn reduces pre-aging kinetics. The optimal pre-aging temperature and time were consequently found to increase when Sn is added. We also studied the effect of adding a further thermal spike to the usual long-term pre-aging, at different positions within the processing route. The results we present are discussed based on a simulation of vacancy evolution in the alloy when subjected to these treatments.

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“…Baking softening means that the hardness of Al alloys decreases when aged in the temperature range of 443 K to 573 K for a few minutes, and the decrease in hardness was attributed to the decomposition of clusters. The subsequent increase in hardness was attributed to the re-formation of large clusters and the β" phase transformed from the clusters [32][33][34].…”

Section: Early Aging Behavior Simulationmentioning

confidence: 99%

Kinetic Monte Carlo Simulation of Clustering in an Al-Mg-Si-Cu Alloy

Zhao

et al. 2021

Materials

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The mechanism of the clustering in Al-Mg-Si-Cu alloys has been a long-standing controversial issue. Here, for the first time, the mechanism of the clustering in the alloy was investigated by a Kinetic Monte Carlo (KMC) approach. In addition, reversion aging (RA) was carried out to evaluate the simulation results. The results showed that many small-size clusters formed rapidly in the early stages of aging. With the prolongation of aging time, the clusters merged and grew. The small clusters formed at the beginning of aging in Al-Mg-Si-Cu alloy were caused by initial vacancies (quenching vacancies). The merging and decomposition of the clusters were mainly caused by the capturing of vacancies, and the clusters had a probability to decompose before reaching a stable size. After repeated merging and decomposition, the clusters reach stability. During RA, the complex interaction between the cluster merging and decomposition leaded to the partial irregular change of the hardness reduction and activation energy.

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Study of retrogression response in naturally and multi-step aged Al-Mg-Si automotive sheets

Cited by 19 publications

References 28 publications

Effects of the Mg/Si Ratio on Microstructure, Mechanical Properties, and Precipitation Behavior of Al–Mg–Si–1.0 wt %-Zn Alloys

Effects of the Mg/Si Ratio on Microstructure, Mechanical Properties, and Precipitation Behavior of Al–Mg–Si–1.0 wt %-Zn Alloys

Effect of Thermal Treatments on Sn-Alloyed Al-Mg-Si Alloys

Kinetic Monte Carlo Simulation of Clustering in an Al-Mg-Si-Cu Alloy

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