Rheological model of semi-solid A356-SiC composite alloys. Part I: Dissociation of agglomerate structures during shear

Mada, M.; Ajersch, F.

doi:10.1016/0921-5093(96)10212-4

Cited by 47 publications

(16 citation statements)

References 18 publications

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“…The reduction of the viscosities is quite small in all three curves, but the thixotropic behavior of semisolid Al-22 pct Si will be more obvious by increasing shear stress. According to Mada et al's study, [13] the thixotropic nature of semisolid alloys is described by Eq. [3].…”

Section: Influence Of Duration Of Shear Stress On the Viscositymentioning

confidence: 99%

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Experimental Investigation on the Rheological Behavior of Hypereutectic Al-Si Alloys by a Precise Rotational Viscometer

Heidary

Akhlaghi

2010

Metall Mater Trans A

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Determining the viscosity of low solid volume fraction semisolid alloys is important for predicting the gradient of primary particles within functionally graded materials (FGMs), produced by in-situ casting processes. In this study, a new precise rotational viscometer was developed and used to measure the viscosity of Al-22 pct Si and Al-30 pct Si semisolid alloys up to solid volume fractions of 9 and 20 pct, respectively. Three kinds of typical curves, viscosity (g) vs solid volume fraction (f s ), shear time (t), and shear rate (_ c), were derived from the results of viscosity measurements for both Al-Si alloys. In the semisolid Al-Si alloys, thixotropic behavior was not detected at low solid volume fractions, but this behavior was obviously observed with increasing solid volume fraction and could be described by an analytical model. Finally, the results showed that the equilibrium viscosity of the semisolid alloys with thixotropic properties decreased by increasing shear rate according to the Ostwald-De Waele power law. A special test, developed in this research, was used to show the effect of agglomeration on the viscosity of the semisolid alloys.

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Section: Influence Of Duration Of Shear Stress On the Viscositymentioning

confidence: 99%

“…Mada et al's study [13] showed that at a constant shear rate, the apparent viscosity (g) decreases as a function of the duration of shear (t) according to Eq. [3]:…”

Section: Introductionmentioning

confidence: 97%

Experimental Investigation on the Rheological Behavior of Hypereutectic Al-Si Alloys by a Precise Rotational Viscometer

Heidary

Akhlaghi

2010

Metall Mater Trans A

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“…Mada and Ajersch [114,115] used this general framework to model the thixotropic behavior of A356 alloys and the effect of SiC particles on it using Eq. 3-37;…”

Section: Modeling Ofthixotropymentioning

confidence: 99%

“…The parameter S varies between 1 and 0, corresponding to the fully agglomerated state and fully deagglomerated state, respectively. The objective of such thixotropic modeling is to derive the time evolution of the structural parameter S.Mada and Ajersch [114,115] used this general framework to model the thixotropic behavior of A356 alloys and the effect of SiC particles on it using Eq. 3-37;…”

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confidence: 99%

rheological behavior of semi-solid A356 alloy /

Lashkari¹

2006

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The semi-solid-metal, SSM, processing deals with semi solid slurries, in which non dendritic solid particles are dispersed in a liquid matrix with apparent viscosity values near to that of liquid. It is able to flow easily under pressure and fills complicated die cavities to manufacture sound as-cast products with high integrity. The SSM slurry is prepared through different methods. In the current study conventional casting and the SEED process were employed to produce SSM billets with different morphologies of primary a-Al phase in A356 Al-Si alloy. For conventional casting, a range of solid particle morphologies, microstructure, were realized through variation of pouring temperature while for the SEED billets, as a new patent of ALCAN international for semi solid casting, changes in the morphology were achieved by control of process parameters during solidification of the melt.In order to investigate the morphological evolution due to the effect of different process parameters, pouring temperature and swirling intensities, the SSM billets prepared by both methods were studied using quantitative metallography. The microstructure of SSM A356 alloy has also been characterized using an innovative method, parallel plate compression viscometry, where a correlation was made between the morphology and viscosity. The main objective of the current research was the implication of rheological principles to study the deformation behavior of A3 5 6 alloy at different morphologies and fraction of solid, while treating the SSM billets as Newtonian and Non-Newtonian fluids respectively. Furthermore, two empirical relationships were proposed to underline the correlation among the viscosity, and fraction solid and its morphology. In order to further confirm the reliability of the tests results in this research and to highlight that the sample size has no effect on the final deformation and viscosity values, a new series of tests were performed using two sets of specimens with aspect ratio (height/diameter) of 0.4 and 1.8.It was found that conventional billets cast at low pouring temperature of 615°C comprise fine and equiaxed grains while the billets cast at high pouring temperature of 695°C have dendritic structure. For SEED billets, swirling refined the primary a-Al dendrites and promoted the formation of rosette and/or globular a-Al particles with increasing swirling speed. The effectiveness of swirling speed may be due to reduction in segregation of alloying elements at the solidification front and better heat transfer between the mold and bulk of liquid to establish a shallow temperature gradient resulting in refining and formation of equiaxed ascast structure. There was no evidence of entrapped eutectic within the primary a-Al particles as one of the advantages of SEED slurry-on-demand technology.The reduction of pouring temperature down to liquidus point, 615°C, improved the flow characteristics of the billets. The calculated viscosity for the billets with globular primary a-Al particles are almost three orders of...

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“…3,39,40,[45][46][47][48][49][50][51] The advantage of a rheometer is that the shear rate in the gap between the bob and the cup can essentially be treated as uniform (but note some concerns which are now emerging 52 ]. A typical experiment would involve stirring the alloy (usually Sn15%Pb as a model because few rheometers will operate at semisolid aluminium temperatures) while cooling from above the liquidus point to the required semisolid temperature (to within 1C) to obtain a non-dendritic microstructure.…”

Section: Rheometrymentioning

confidence: 99%

Semisolid processing of metallic materials

Atkinson

2010

Materials Science and Technology

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Abstract. Semi-solid processing involves forming metallic alloys between the solidus and the liquidus. For the process to operate, the microstructure must consist of solid spheroids in the liquid matrix, rather than dendrites. The material then flows when it is sheared but thickens again when allowed to stand, i.e. it behaves thixotropically. This type of behaviour was first discovered by Flemings and co-workers in the 1970s and is utilized in a family of processes, some now applied commercially. Here the current status of semisolid processing, both technologically and from a research point of view, will be reviewed.

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Rheological model of semi-solid A356-SiC composite alloys. Part I: Dissociation of agglomerate structures during shear

Cited by 47 publications

References 18 publications

Experimental Investigation on the Rheological Behavior of Hypereutectic Al-Si Alloys by a Precise Rotational Viscometer

Experimental Investigation on the Rheological Behavior of Hypereutectic Al-Si Alloys by a Precise Rotational Viscometer

rheological behavior of semi-solid A356 alloy /

Semisolid processing of metallic materials

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