Characterisation of the rheological behaviour in the semi-solid state of grain-refined AZ91 magnesium alloys

Gebelin, Jean‐Christophe; Suéry, M.; Favier, Denis

doi:10.1016/s0921-5093(99)00467-0

Cited by 67 publications

(29 citation statements)

References 2 publications

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“…These models are able to predict phase separation [e.g. 118,149]. However, the determination of the rheological parameters which are required is not straightforward [e.g.…”

Section: 32two Phase Finite Elementmentioning

confidence: 99%

Modelling the semisolid processing of metallic alloys

Atkinson

2005

Progress in Materials Science

518

160

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Semi-solid processing of metallic alloys and composites utilises the thixotropic behaviour of materials with non-dendritic microstructure in the semi-solid state. The family of innovative manufacturing methods based on this behaviour has been developing over the last twenty years or so and originates from scientific work at MIT in the early 1970s. Here, a summary is given of:-routes to spheroidal microstructures; types of semi-solid processing; and advantages and disadvantages of these routes.Background rheology and mathematical theories of thixotropy are then covered as precursors to the main focus of the review on transient behaviour of semi-solid alloy slurries and computational modelling. Computational Fluid Dynamics (CFD) can be used to predict die filling. However, some of the reported work has been based on rheological data obtained in steady state experiments, where the semi-solid material has been maintained at a particular shear rate for some time. In reality, in thixoforming, the slurry undergoes a sudden increase in shear rate from rest to 100s -1 or more as it enters the die. This change takes place in less than a second. Hence, measuring the transient rheological response under rapid changes in shear rate is critical to the development of modelling of die filling and successful die design for industrial processing. The modelling can be categorised as one phase or two phase and as finite difference or finite element. Recent work by Alexandrou and co-workers and, separately Modigell and co-workers, has led to the production of maps which, respectively summarise regions of stable/unstable flow and regions of laminar/transient/turbulent fill. These maps are of great potential use for the prediction of appropriate process parameters and avoidance of defects. A novel approach to modelling by Rouff and coworkers involves micro-modelling of the 'active zone' around spheroidal particles.There is little quantitative data on the discrepancies or otherwise between die fill simulations and experimental results (usually obtained through interrupted filling).There are no direct comparisons of the capabilities of various software packages to model the filling of particular geometries accurately. In addition, the modelling depends on rheological data and this is sparse, particularly for the increasingly complex two-phase models. Direct flow visualisation can provide useful insight and avoid the effects of inertia in interrupted filling experiments.

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“…These models are able to predict phase separation [e.g. 118,149]. However, the determination of the rheological parameters which are required is not straightforward [e.g.…”

Section: 32two Phase Finite Elementmentioning

confidence: 99%

Modelling the semisolid processing of metallic alloys

Atkinson

2005

Progress in Materials Science

518

160

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“…Rapid epitaxial solidification onto the primary α-Mg grains was expected due to the limited cooling rate during quenching [12,13,[18][19][20][21][22][23][24][25][26]. This solid deposition is visible in Figure 4 for specimens preheated using Cycle A where a thin but continuous layer of α-phase encloses particles of β-phase formed within α-Mg grain upon quenching.…”

Section: Microstructure Of Quenched Specimensmentioning

confidence: 99%

“…Moreover, no assumption about any thermophysical property of the alloys is required. However overestimation of the solid fraction caused by a substantial solid deposition on to the primary phase during quenching was reported frequently [12,13,[18][19][20][21][22][23][24][25]. It was observed that high cooling rates (160 K/s) during quenching of small aluminum specimens can prevent this phenomenon efficiently [21].…”

Section: Introductionmentioning

confidence: 99%

DETERMINATION OF THE THIXOCASTING TEMPERATURES OF AZ91D AND OTHER Mg ALLOYS USING A QUENCHING METHOD

Giguère¹,

Amira²,

Tremblay³

et al. 2008

Canadian Metallurgical Quarterly

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Determination of the thixocasting temperatures of AZ91D and other Mg alloys using a quenching method Giguère, N.; Amira, S.; Tremblay, R.; Loong, C. A.; Dubé, D.Contact us / Contactez nous: nparc.cisti@nrc-cnrc.gc.ca. Abstract -The thixocasting injection temperature is a crucial processing parameter, frequently unavailable in the literature, especially for newly developed alloys. In this work, a simple and rapid method derived from the quenching method was developed to obtain an acceptable thixocasting injection temperature range for various magnesium alloys: AZ91D, AJ62x, AXJ530, MRI153 and ZAEX10440. Small specimens of each alloy were heated to appropriate temperatures within the semisolid range and quenched. Their microstructure was observed optically and the proportion of phase was measured using quantitative image analysis. The microsegregation was characterized and two different heating cycles prior to quenching were studied. The apparent volume fraction of the primary solid was determined as a function of quenching temperature between liquidus and solidus. These results were found useful to obtain a practical injection temperature range for each alloy and to obtain good quality thixocast parts.Résumé -La température d'injection pour la thixocoulée est un paramètre crucial de procédé qui n'est pas toujours disponible dans la littérature et ce, surtout dans le cas de nouveaux alliages développés en laboratoire. Dans cet article, une méthode simple et rapide, dérivée de la méthode de trempe, est proposée pour estimer un intervalle de température d'injection d'alliages de magnésium tels que AZ91D, AJ62x, AXJ530, MRI153 et ZAEX10440. Des spécimens de chaque alliage ont été chauffés à différentes températures dans l'intervalle semisolide et trempés. Leur microstructure a été observée en microscopie optique et analysée quantitativement par analyse d'image afin de mesurer la proportion de la phase solide primaire. La microségrégation a également été mesurée dans les phases après trempe et deux cycles thermiques différents ont été comparés. La fraction volumique apparente de la phase solide primaire a été déterminée en fonction de la température de trempe entre le liquidus et le solidus. À partir de ces résultats, un intervalle de température a été estimé pour chaque alliage afin d'obtenir par thixocoulée des pièces d'excellente qualité.

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“…The fluid flow behaviour of semi-solid slurry has been investigated using a variety of characterization techniques. These include rotational viscometry [27], capillary rheometry [28][29], indentation [30][31], back extrusion [32][33][34], and compression between parallel plates [35].…”

Section: Introductionmentioning

confidence: 99%

Rheological behavior and microstructural evolution of semi-solid hypereutectic Al-Si-Mg-Cu alloys using rheoforming process /

Tebib¹

2012

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Over the last three decades the semi-solid metal (SSM) processing has received significant attention. Semi-solid processing involves the net shape manufacturing of alloys in the semi-solid state. The principal attraction for the process has been the unique rheology of the slurry which induces better movement of materials through the die and allows intricate thin-wall near net shape components to be cast at lower applied pressures. This behaviour offers considerable advantages to the quality of castings. The reduced oxide entrapment, low porosity and a lower operating temperature make semi-solid processing ideal for the forming of high integrity parts.The aim of the current study was to investigate the rheological behavior and microstructural evolution of hypereutectic Al-Si-Cu and Al-Si-Mg-Cu alloys using conventional and modified SEED process (Swirled Enthalpy Equilibration Device). This project is divided into four parts.

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Characterisation of the rheological behaviour in the semi-solid state of grain-refined AZ91 magnesium alloys

Cited by 67 publications

References 2 publications

Modelling the semisolid processing of metallic alloys

Modelling the semisolid processing of metallic alloys

DETERMINATION OF THE THIXOCASTING TEMPERATURES OF AZ91D AND OTHER Mg ALLOYS USING A QUENCHING METHOD

Rheological behavior and microstructural evolution of semi-solid hypereutectic Al-Si-Mg-Cu alloys using rheoforming process /

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