The Natural and Artificial Aging Response of Semi-Solid Metal Processed Alloy A356

Möller, Heinrich; Govender, Gonasagren; Stumpf, Waldo E.

doi:10.4028/www.scientific.net/ssp.141-143.737

Cited by 23 publications

(40 citation statements)

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“…It is seen that the material has a globular primary grain structure and a fine eutectic, similar to the as cast microstructure of SSM-HPDC A356. [12][13][14][15] Solution treatment at 540uC results in the eutectic structure changing to a globular type structure ( Fig. 2b and c).…”

Section: Resultsmentioning

confidence: 99%

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Comparison of heat treatment response of semisolid metal processed alloys A356 and F357

Möller

Govender

Stumpf

et al. 2010

International Journal of Cast Metals Research

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The heat treatment response of semisolid metal high pressure die cast Al-7Si-Mg alloys A356 and F357 was studied and compared. It was found that the heat treatment behaviour of alloy F357 is influenced markedly by the stability of the Mg containing p phase. This phase, which dissolves in alloy A356 during solution treatment, persists in F357 and decreases the amount of magnesium in solid solution. This is the likely origin of the decrease in the aging response of the F357 alloy. The tensile properties (yield strength and ultimate tensile strength) of the alloys correlate much better with the Mg concentration in solid solution than with the bulk Mg content of the alloys. The recently developed shortened T6 heat treatment cycles for rheocast A356 were tested on alloy F357. The optimum artificial aging treatment was determined to be 180uC for 4 h, regardless of the prior natural aging period.

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Section: Resultsmentioning

confidence: 99%

“…Second, the suitability of previously developed optimised A356 heat treatment cycles [12][13][14][15] for the SSM-HPDC alloy F357 was also investigated.…”

Section: Introductionmentioning

confidence: 99%

Comparison of heat treatment response of semisolid metal processed alloys A356 and F357

Möller

Govender

Stumpf

et al. 2010

International Journal of Cast Metals Research

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“…In Al-7Si-Mg casting alloys, natural pre-ageing causes a sluggish age-hardening response during subsequent artificial ageing, but interestingly, the extent of the loss in hardness is fully recovered 5 upon further artificial ageing [17][18][19]. To date, there is a lack of detailed research revealing precipitate micro-and nanostructural evolution during ageing of Al-Si-Mg casting alloys.…”

Section: Introductionmentioning

confidence: 99%

Solute nanostructures and their strengthening effects in Al–7Si–0.6Mg alloy F357

et al. 2012

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The solute-nanostructures formed in the primary α-Al grains of a Semi-Solid Metal cast Al-7Si-0.6Mg alloy (F357) during ageing at 180°C, and the age-hardening response of the alloy have been systematically investigated using transmission electron microscopy, atom probe tomography and hardness testing. A 120-h natural pre-ageing led to the formation of solute clusters and GP zones. The natural pre-ageing slowed down the precipitation kinetics six-fold during 1 h ageing at 180°C, but this effect diminished after 4 h when the sample reached the same hardness as that without the pre-ageing treatment. It reduced the number density of β″-needles to approximately half of that formed in samples without the treatment, and postponed the peak hardness occurrence to 4 h, 4 times that of the as-quenched sample. A hardness plateau developed in the as-quenched sample between 1 h and 4 h ageing corresponds to the growth of 2 the β″ precipitates and a significant concurrent decrease of solute clusters and GP zones. The average Mg:Si ratio of early solute clusters is < 0.7 while that of GP zones changes from 0.8 to 0.9 with increasing in their size, and that of β″-needles increases from 0.9 to 1.2. β″-needles, GP zones and solute clusters are important strengthening solute nanostructures of the alloy. The partitioning of solutes and precipitation kinetics of the alloy are discussed in detail.

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“…1 for (a) The globular primary α-Al structure is retained in all the samples during heat treatment with spheroidisation of the eutectic silicon occurring during solution treatment in the casting alloys as shown in Fig. 2 [4,7]. Fig.…”

Section: Resultsmentioning

confidence: 97%

“…The tensile mechanical properties of SSM-HPDC alloys 6082, 6004, A356 and F357 are shown in Table 2. An artificial aging time at 180 o C of 4 h was used for A356 and F357 [4,7] and 8 hours for 6082 and 6004 (Fig. 3).…”

Section: Resultsmentioning

confidence: 99%

Comparison of the Heat Treatment Response of SSM-HPDC 6082 and 6004 Wrought Alloys with A356 and F357 Casting Alloys

Möller¹,

Govender²,

Stumpf

2011

MSF

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Semi-solid metal high pressure die casting was used to produce plates from traditional wrought AlMg-Si alloys 6082 and 6004, as well as from traditional casting Al-Si-Mg alloys A356 and F357. The high Si-content of the casting alloys offer several advantages, including a faster artificial aging response, higher strength for comparable Mg contents and less sensitivity to prior natural aging on peak strength. However, over-aging occurs earlier in the casting alloys than in the wrought alloys. IntroductionThe Al-Si-Mg alloys that constitute the 6000 series wrought alloys and 300 series casting alloys are heat treatable and depend on age-hardening to develop enhanced strength properties [1]. The main difference between the 300 series and 6000 series is the Si content, with the casting alloys containing a significantly higher quantity [1]. Silicon promotes castability mainly because of the high fluidity imparted by the presence of large volumes of the Al-Si eutectic [1]. The lack of research on the precipitation sequence in Al-Si-Mg casting alloys compared with the Al-Mg-Si wrought alloys has recently been highlighted [2]. In Al-Si-Mg alloys in general, the decomposition of the supersaturated solid solution (SSS) is believed to occur as follows [3]: SSS → (Mg + Si) clusters / GP(I) spherical → β″ / GP (II) needles → β rods ′ → β plates , where GP = Guinier-Preston zones, β = equilibrium Mg 2 Si, β′ and β″ = metastable precursors of β. Semi-solid metal (SSM) processing is a unique manufacturing method to produce near-net shape products for various industrial applications. The aim is to obtain a semi-solid structure which is free of dendrites and with the solid constituent present in a near spherical form. Casting alloys A356/7 are probably the most popular alloys used for SSM forming [4], but one of the main advantages of SSM processing is that it is also possible to produce near net-shape components from alloys that are conventionally wrought such as the 6000 series [5]. The purpose of this paper is to compare the aging response of 6000 series wrought alloys with A356/7 casting alloys produced with the same processing technique with the advantage of having comparable globular primary α-Al microstructures.

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The Natural and Artificial Aging Response of Semi-Solid Metal Processed Alloy A356

Cited by 23 publications

References 4 publications

Comparison of heat treatment response of semisolid metal processed alloys A356 and F357

Comparison of heat treatment response of semisolid metal processed alloys A356 and F357

Solute nanostructures and their strengthening effects in Al–7Si–0.6Mg alloy F357

Comparison of the Heat Treatment Response of SSM-HPDC 6082 and 6004 Wrought Alloys with A356 and F357 Casting Alloys

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