Simple rheocasting processes

Haga, Toshio; Kapranos, P.

doi:10.1016/s0924-0136(02)00819-1

Cited by 128 publications

(81 citation statements)

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“…The microstructure was less globular compare with the sample produced with a pouring temperature of 630°C. This was confirms that size of primary grains was affected with a low fraction solid used [17].…”

Section: Effects Of Holding Timesupporting

confidence: 75%

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The Effect of Direct Thermal Method, Temperature and Time on Microstructure of a Cast Aluminum Alloy

Ahmad

Naher

Brabazon

2014

Materials and Manufacturing Processes

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The direct thermal method is used for the creation of globular microstructures suitable for semi-solid metal forming. In this paper both simulation and experimental results using direct thermal method are presented.ProCAST® software was used to estimate temperature distribution inside the aluminium billet. In validation work, molten aluminium A356 was poured into metallic copper tube moulds and cooled down to the semi-solid temperature before being quenched in water at room temperature. The effect of pouring temperatures of 630°C, 650°C, 665°C, 680°C and holding times of 45s and 60s on the microstructure of aluminium A356 alloy were investigated. The simulation results showed that the average temperature rate within the copper mould, from initial pouring temperature to just before quenching, was approximately 1°C/s. Examination of the solidified microstructures showed that the microstructure was more spherical when lower pouring temperatures and holding periods were used. From the micrographs it was found that the most globular and smallest structures were achieved at processing parameters of 630°C and 45s.

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Section: Effects Of Holding Timesupporting

confidence: 75%

“…Formation of globular microstructure was influenced by fraction solid [17]. The sample with a 630°C pouring temperature was quenched at 570°C, equivalent to 0.65 fraction solid.…”

Section: Effects Of Holding Timementioning

confidence: 99%

The Effect of Direct Thermal Method, Temperature and Time on Microstructure of a Cast Aluminum Alloy

Ahmad

Naher

Brabazon

2014

Materials and Manufacturing Processes

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“…Knowledge of this point therefore allows a better understanding of material behaviour and determination of a suitable temperature for processing. Optimum fraction solids for thixoforging have been noted to be within the range of 0.3 to 0.5 [22,23]. Delaying DCP to a lower temperature and higher fraction solid, by utilisation of a lower cooling rate, has the advantage of extending the temperature and fraction solid range over which the semi-solid material can be processed [17].…”

Section: Effect Of Cooling Rate On Solidificationmentioning

confidence: 99%

Thermal Profiles and Fraction Solid of Aluminium 7075 at Different Cooling Rate Conditions

Ahmad

Naher

Brabazon

2013

KEM

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Abstracts:In order to determine suitable processing conditions for semi-solid aluminium 7075 thermal analysis (TA) was performed in order to obtain the relationship between fraction solid and temperature. During experimental work, the alloy was heated to 750°C by resistance heated box furnace and solidified at various cooling rates. Cooling curves for the metal were recorded with two thermocouples, one at the centre of the melt volume and one beside the containing crucible wall. A specially designed chamber with kaowool blanket was used to achieve the slowest cooling rate. The faster cooling rate was achieved with the crucible in open atmosphere with a set air flow rate over the crucible. A Data Acquisition (DAQ) system controlled by LabVIEW software was used to record the temperature-time profiles. From these cooling curves, the phase change at any corresponding time and temperature was estimated. The temperature difference between centre and wall of crucible was used to determine dendritic coherency point (DCP). Results show that, the slowest cooling rate with the kaowool blanket was at 0.03°C/s. An intermediate cooling rate of 0.21°C/s was achieved by leaving the melt to cool without kaowool blanket or forced air flow, and the fastest cooling rate was 0.43°C/s. The change in cooling rate altered the temperatures at which phase changes occurred, including those for eutectic and solidus. It was found that for lower the cooling rates that the DCP occurred at lower temperatures. The DCP for the cooling rate of 0.03°C/s was found to be 574°C (corresponding to 0.85 fraction solid) whereas the DCP for 0.43°C/s was found to be 623°C (corresponding to 0.55 fraction solid).

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“…Formation of seeds during the movement on the inclined plate just before entering into the mold fabricates a suitable microstructure for the rheocast material. Haga et al [49] have also proposed the new and 28 simple rheocasting method by using low superheat alloys. They poured the melt at low temperatures into a metallic die to produce a semi final shape which was ram extruded to its final shape while still at semi solid state.…”

Section: Non Agitation Processesmentioning

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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Simple rheocasting processes

Cited by 128 publications

References 0 publications

The Effect of Direct Thermal Method, Temperature and Time on Microstructure of a Cast Aluminum Alloy

The Effect of Direct Thermal Method, Temperature and Time on Microstructure of a Cast Aluminum Alloy

Thermal Profiles and Fraction Solid of Aluminium 7075 at Different Cooling Rate Conditions

rheological behavior of semi-solid A356 alloy /

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