Study of precipitation kinetics in a super purity Al-0.8 pct Mg-0.9 pct Si alloy using differential scanning calorimetry

Gupta, Archana; Lloyd, D. J.

doi:10.1007/s11661-999-0081-1

Cited by 38 publications

(71 citation statements)

References 19 publications

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“…On the basis of those different behaviors, nanoclusters formed at the initial and middle stages of NA should be distinguished in this study. Based on previously reported results that Si-rich cluster is initially formed and magnesium atoms incorporate into Si-rich clusters with increasing NA time 38,40,41) and the present experimental results, the present authors believe that Si-rich clusters are formed at the initial stage and Mg-Si co-clusters are formed at the middle stage, respectively. Si-rich clusters are thermally stable and harmful to form the ¢AA phase, while Mg-Si co-clusters are thermally unstable and useful to form the ¢AA phase during the two-step aging at 170°C, respectively.…”

Section: Thermal Stability Of Nanoclusters and Their Transition Behavsupporting

confidence: 77%

“…Serizawa et al 38) explained that the Si-rich clusters are initially formed, then the magnesium atoms incorporate into the nanoclusters with increasing the NA time. Gupta et al 40) and Chang et al 26,27) calculated the binding energies of vacancies and impurities in the aluminum matrix. They used the chemical interaction energies defined as a total-energy changes because of the atomic rearrangement.…”

Section: Discussionmentioning

confidence: 99%

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Influence of Natural Aging Time on Two-Step Aging Behavior of Al-Mg-Si(-Cu) Alloys

2015

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Nanoclusters formed during natural aging cause the negative effect of the two-step aging in the age-hardenable Al-Mg-Si alloys. The relationship between the clustering behavior during natural aging and the two-step aging behavior was studied using the hardness, differential scanning calorimetry (DSC), electrical resistivity measurements, transmission electron microscopy (TEM) observation in the Cu-free and Cuadded Al-Mg-Si alloys. Three stages during the two-step aging are clearly revealed based on the hardness results. The hardness in the two-step aging with the natural aging time is decreased, increased and then decreased at the initial, middle and final stages, respectively. Si-rich clusters initially formed during natural aging do not transform into the ¢AA phase and are thermally stable during the two-step aging at 170°C. On the other hand, Mg-Si co-clusters formed at the middle stage during natural aging transform into the ¢AA phase and are thermally unstable during the twostep aging at 170°C. Much higher hardness is obtained in the Cu-added alloy than that of the Cu-free alloy during two-step aging when natural aging is performed for 3.6 ks belonging to the initial stage. The higher hardness is also found to be obtained during over-aging regardless of the natural aging time in the Cu-added alloy than that of the Cu-free alloy. The relationship between the clustering behavior during natural aging and the two-step aging behavior is discussed based on the observed age-hardening phenomena.

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Section: Thermal Stability Of Nanoclusters and Their Transition Behavsupporting

confidence: 77%

Section: Discussionmentioning

confidence: 99%

Influence of Natural Aging Time on Two-Step Aging Behavior of Al-Mg-Si(-Cu) Alloys

2015

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“…Peak 2, however, still remains as a shoulder in the DSC curves naturally aged for 1.04 © 10 4 and 4.48 © 10 4 ks. Both of Peak 2 and Peak 2A are due to the formation of ¢″, 2,10) therefore it is understood that the formation of the ¢″ phase occurs in the two stages in these conditions. The formation behavior of the ¢″ phase must be affected by the natural aging.…”

Section: Resultsmentioning

confidence: 98%

Effects of Natural Aging on Bake Hardening Behavior of Al–Mg–Si Alloys with Multi-Step Aging Process

et al. 2014

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In the present paper, the effects of natural aging on the bake hardening behavior of four AlMgSi alloys, i.e., Alloy A (Al0.6Mg0.6Si) (mass%), Alloy B (Al0.6Mg1.0Si), Alloy C (Al1.0Mg0.6Si) and Alloy D (Al1.0Mg1.0Si), were investigated by means of Vickers hardness test, tensile test, differential scanning calorimetry analysis (DSC) and transmission electron microscopy (TEM). Two kinds of nanoclusters, i.e., Cluster(1) and Cluster(2) were controlled with the multi-step aging process. As the results, it was found that Cluster(1) formed during natural aging caused the decreased bake hardening response even though the pre-aging was conducted before natural aging. The decrease of the bake hardening response with increasing the natural aging time was markedly higher in the later stage of bake hardening than in the early stage. Exothermic peaks of Peak 2 and Peak 2A were observed in all of four alloys pre-aged at 343 and 363 K. Peak 2A became larger with the natural aging time. The size distribution of the ¢″ precipitates became wider with the natural aging time for Alloy A heated up to the temperature of Peak 2A. This is well understood by the following model. The transition from Cluster(2) formed during pre-aging to ¢″ occurs preferentially at the early stage of bake hardening or during heating up to the temperature of Peak 2. Then the growth of ¢″ is inhibited by the presence of Cluster(1) at the later stage of bake hardening. The secondary nucleation of ¢″ occurs just after the dissolution of Cluster(1) into the matrix during heating up to the temperature of Peak 2A. The combined formation of Cluster(1) and Cluster(2) by the multi-step aging essentially affects the BH response and the ¢″ precipitates in AlMgSi alloys.

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“…[39,40] Therefore, atomistic modeling is most commonly employed to capture the cluster evolution, [40,41] although simpler models based on the KampmannWagner formalism and the Johnson-Mehl-AvramiKolmogorov (JMAK) equation also exist. [31,42,43] Note that the latter two approaches assume that the cluster formation can be treated as a classic nucleation and growth process, which clearly is an oversimplification of the problem. Still, a natural aging model based on the Kampmann-Wagner formalism is deemed to be the best choice in the present context, since such a model would be fully compatible with the other NaMo models and therefore easy to implement into the existing mathematical framework.…”

Section: Modeling Strategymentioning

confidence: 99%

An Extended Age-Hardening Model for Al-Mg-Si Alloys Incorporating the Room-Temperature Storage and Cold Deformation Process Stages

Myhr

Grong

Schäfer

2015

Metall Mater Trans A

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In this article, a new age-hardening model for Al-Mg-Si alloys is presented (named NaMo-Version 2), which takes into account the combined effect of cold deformation and prolonged room-temperature storage on the subsequent response to artificial aging. As a starting point, the original physical framework of NaMo-Version 1 is revived and used as a basis for the extension. This is permissible, since a more in-depth analysis of the underlying particle-dislocation interactions confirms previous expectations that the simplifying assumption of spherical precipitates is not crucial for the final outcome of the calculations, provided that the yield strength model is calibrated against experimental data. At the same time, the implementation of the Kampmann-Wagner formalism means that the different microstructure models can be linked together in a manner that enforces solute partitioning and competition between the different hardening phases which form during aging (e.g., clusters, b¢¢ and b¢). In a calibrated form, NaMo-Version 2 exhibits a high degree of predictive power, as documented by comparison with experiments, using both dedicated nanostructure and yield strength data as a basis for the validation. Hence, the model is deemed to be well-suited for simulation of thermomechanical processing of Al-Mg-Si alloys involving cold-working operations like sheet forming and stretch bending in combination with heat treatment and welding.

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Study of precipitation kinetics in a super purity Al-0.8 pct Mg-0.9 pct Si alloy using differential scanning calorimetry

Cited by 38 publications

References 19 publications

Influence of Natural Aging Time on Two-Step Aging Behavior of Al-Mg-Si(-Cu) Alloys

Influence of Natural Aging Time on Two-Step Aging Behavior of Al-Mg-Si(-Cu) Alloys

Effects of Natural Aging on Bake Hardening Behavior of Al–Mg–Si Alloys with Multi-Step Aging Process

An Extended Age-Hardening Model for Al-Mg-Si Alloys Incorporating the Room-Temperature Storage and Cold Deformation Process Stages

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Study of precipitation kinetics in a super purity Al-0.8 pct Mg-0.9 pct Si alloy using differential scanning calorimetry

Cited by 38 publications

References 19 publications

Influence of Natural Aging Time on Two-Step Aging Behavior of Al-Mg-Si(-Cu) Alloys

Influence of Natural Aging Time on Two-Step Aging Behavior of Al-Mg-Si(-Cu) Alloys

Effects of Natural Aging on Bake Hardening Behavior of Al&ndash;Mg&ndash;Si Alloys with Multi-Step Aging Process

An Extended Age-Hardening Model for Al-Mg-Si Alloys Incorporating the Room-Temperature Storage and Cold Deformation Process Stages

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Effects of Natural Aging on Bake Hardening Behavior of Al–Mg–Si Alloys with Multi-Step Aging Process