Quench Sensitivity of an Al-7 Pct Si-0.6 Pct Mg Alloy: Characterization and Modeling

Tiryakioğlu, Murat; Shuey, R. T.

doi:10.1007/s11663-007-9027-4

Cited by 42 publications

(24 citation statements)

References 23 publications

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“…If the quench rate is sufficiently high a high concentration of solute in solid solu dislocations, whi lower maximum yield strength after ageing. In Al-Si casting alloys; Si may diffuse from the matrix to eutectic Si particles and Mg 2 Si phases may form on the eutectic Si particles or in the matrix, reducing the supersaturation of Mg and Si in the matrix [29].…”

Section: Quenchmentioning

confidence: 99%

The heat treatment of Al–Si–Cu–Mg casting alloys

Sjölander

Seifeddine

2010

Journal of Materials Processing Technology

460

223

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Environmental savings can be made by increasing the use of aluminium alloys in the automotive industry as the vehicles can be made lighter. Increasing the knowledge about the heat treatment process is one task in the direction towards this goal. The aim of this work is to investigate and model the heat treatment process for Al-Si casting alloys. Three alloys containing Mg and/or Cu were cast using the gradient solidification technique to achieve three different coarsenesses of the microstructure and a low amount of defects.Solution treatment was studied by measuring the concentration of Mg, Cu and Si in the α-Al matrix using wavelength dispersive spectroscopy (WDS) after various times at a solution treatment temperature. A diffusion based model was developed which estimates the time needed to obtain a high and homogenous concentration of alloying elements for different alloys, temperatures and coarsenesses of the microstructure. It was shown that the yield strength after artificial ageing is weakly dependent on the coarseness of the microstructure when the solution treatment time is adjusted to achieve complete dissolution and homogenisation.The shape and position of ageing curves (yield strength versus ageing time) was investigated empirically in this work and by studying the literature in order to differentiate the mechanisms involved. A diffusion based model for prediction of the yield strength after different ageing times was developed for Al-Si-Mg alloys. The model was validated using data available in the literature. For Al-Si-Cu-Mg alloys further studies regarding the mechanisms involved need to be performed.Changes in the microstructure during a heat treatment process influence the plastic deformation behaviour. The Hollomon equation describes the plastic deformation of alloys containing shearable precipitates well, while the Ludwigson equation is needed when a supersaturated solid solution is present. When non-coherent precipitates are present, none of the equations describe the plastic deformation well. The evolution of the storage rate and recovery rate of dislocations was studied and coupled to the evolution of the microstructure using the Kocks-Mecking strain hardening theory.

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Section: Quenchmentioning

confidence: 99%

The heat treatment of Al–Si–Cu–Mg casting alloys

Sjölander

Seifeddine

2010

Journal of Materials Processing Technology

460

223

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“…This method has been applied to data sets for aluminum alloy 2024 from the literature in this article. The results showed the following: Constant inversely proportional to number of nucleation sites or particles (s) K 3 Constant directly proportional to energy barrier for heterogeneous nucleation (J/mol) K 4 Constant related to solvus temperature (K) r int Yield strength at complete solute loss to quench precipitates (MPa) r min (T) Yield strength with fast quench interrupted by equilibration at temperature T (MPa) r max Yield strength obtained with quenching at an infinite rate (MPa) q Electrical resistivity measured immediately after quench (mx.cm)…”

Section: Discussionmentioning

confidence: 99%

“…The improved model, which was recently applied [3] to D357-T6 cast aluminum alloy, (1) establishes process-structure-property relationships, (2) accommodates multiple quench precipitates, and (3) uses thermodynamic and calculated data for certain coefficients. The evolution of the amount of each type of quench precipitate is represented by a unitless microstructural state variable S. For no precipitation during the quench (infinite cooling rate), S = 0.…”

Section: B the Improved Model For Quench Sensitivitymentioning

confidence: 99%

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Modeling Quench Sensitivity of Aluminum Alloys for Multiple Tempers and Properties: Application to AA2024

Tiryakioğlu

Shuey

2010

Metall Mater Trans A

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Quench factor analysis (QFA) was developed to predict the change in certain properties, such as yield strength, hardness, electrical conductivity, etc., with how the material cools from solution treatment temperature during quenching. This method necessitates that a set of coefficients be developed by laboratory testing for a particular alloy in a given temper. In the original QFA, these coefficients have been developed independently for each physical property of each temper that might be produced from the same alloy. However, properties used commonly to assess quench sensitivity, e.g., electrical resistivity, hardness tests, tensile tests in different directions, etc., all respond to the same physical change during quench: loss of solute caused by the precipitation of quench precipitates. The QFA method has been modified to handle multiple properties and multiple tempers. The new method allows multiple C-curves for multiple phases and/or nucleation mechanisms for quench precipitates. The advantages of this method include better statistical resolution when fitting multiple data concurrently and possible substitution of a cheaper test for the property and temper of interest. The use of this approach is demonstrated on data sets for aluminum alloy 2024 within this study.

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“…more prone to form precipitates during quench, compared to wrought alloys [2,5]. This is explained with the presence of eutectic Si particles in casting alloys [2]. The concentration of Si in solid solution in the matrix is reduced with reduced quench rates due to diffusion of Si atoms to eutectic Si particles.…”

Section: Introductionmentioning

confidence: 99%

Influence of Quench Rate on the Artificial Ageing Response of an Al-8Si-0.4Mg Cast Alloy

Sjölander

Seifeddine

Fracasso

2015

MSF

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The aim of the study is to present the influence of quench rate on the artificial ageing response of Al-8%Si-0.4%Mg cast alloy in terms of Brinell hardness and yield strength. The investigated material was produced by a gradient solidification technique and exhibited a microstructure that corresponds to the one of gravity die castings, with a dendrite arm spacing of approximately 25 µm. The study comprises two solution treatment temperatures, five quench rates and artificial ageing times exceeding 100 hours at 170 and 220 ⁰C. The microstructure and concentration profiles of Mg and Si were evaluated using energy and wavelength dispersive spectroscopy. Microstructural examination reveals an increment of solutes in the Al-matrix when higher solution treatment temperatures accompanied with high quench rates are applied and shows how both Si and Mg atoms have diffused towards the eutectic during quenching. Consequently, i.e. by increasing the levels of solutes and vacancies, the highest strength levels were realized. The study confirmed that quench rates above 2 ⁰C /s do not offer substantial strength improvement while quenching at lower rates resulted in a lower peak hardness and longer times to peak. IntroductionA T6 heat treatment is often conducted to obtain an increase in strength of cast Al-Si-Mg alloys. A T6 heat treatment consists of a solution treatment, a quench and an artificial ageing. The objective of quenching is to suppress precipitation upon cooling of the casting from the high solution treatment temperature to room temperature. A fast quench results in a high supersaturation of solute and vacancies and a high strength after ageing. If the cooling is slow, precipitates or second phases will form heterogeneously on dislocations or grain boundaries during cooling, which results in a reduction in supersaturation and concomitantly a lower strength after ageing. A high supersaturation as well as a high diffusion rate are needed for the precipitation to take place. These two properties have opposite temperature dependence and the highest nucleation and growth rates thereby occur at intermediate temperatures between 450 °C and 200 °C for most . The time spent in this temperature region during quenching should therefore be as short as possible to avoid precipitation.

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Quench Sensitivity of an Al-7 Pct Si-0.6 Pct Mg Alloy: Characterization and Modeling

Cited by 42 publications

References 23 publications

The heat treatment of Al–Si–Cu–Mg casting alloys

The heat treatment of Al–Si–Cu–Mg casting alloys

Modeling Quench Sensitivity of Aluminum Alloys for Multiple Tempers and Properties: Application to AA2024

Influence of Quench Rate on the Artificial Ageing Response of an Al-8Si-0.4Mg Cast Alloy

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