Rheology and microstructural development of a Al–4wt%Cu alloy in the semi-solid state

Ferrante, M.; Freitas, E. de

doi:10.1016/s0921-5093(99)00226-9

Cited by 57 publications

(36 citation statements)

References 17 publications

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“…This could be an attractive route for the production of inexpensive starting materials for semi solid forming as investigated by several workers [28,38]. Although suitable structures have been produced in aluminum alloys using standard grain refiners, it appears to be difficult to obtain grain sizes less than 100 urn and questions of recycleability of the alloys have been raised [38].…”

Section: Non Agitation Processesmentioning

confidence: 99%

“…Other researchers [28,67] have used the equation 2-4 as a dimensionless parameter to indicate the sphericity of the grains…”

Section: Metallographymentioning

confidence: 99%

“…Although grain refining has not a great effect on the morphology of primary a-Al phases it is somehow used to fabricate the suitable feedstock for thixocasting processes. It seems that the feedstock which are prepared by grain refiner additions have shown better globularity in microstructure after reheating of the billets than non grain refined billets [28].…”

mentioning

confidence: 99%

“…Grain refinement causes smaller particle size and better distribution of a-Al primary phases within SSM slurry, thus the obtained material may show lower viscosity and better flow behavior [28]. Small size of primary phases reduces the collision rate amongst the particles and extends the free moving time of a-Al phase within samples, which is seen as the lower viscosity of slurry during rheological test.…”

mentioning

confidence: 99%

“…Indentation test is another simple way to study mechanical properties of slugs [28]. In this method, the depth of penetration of a steel cylinder under a constant pressure in the semi solid billet is taken as an indication of viscosity of the alloy.…”

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confidence: 99%

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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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Section: Non Agitation Processesmentioning

confidence: 99%

“…Other researchers [28,67] have used the equation 2-4 as a dimensionless parameter to indicate the sphericity of the grains…”

Section: Metallographymentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%