Semisolid Casting of AlSi7Mg0.35 Alloy Produced by Low-Temperature Pouring

Wang, H.; Davidson, Cameron; Taylor, J. A.; StJohn, David H.

doi:10.4028/www.scientific.net/msf.396-402.143

Cited by 19 publications

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“…In this case, the grain size can reduce substantially without a significant change in the SDAS and consequently a more globular morphology is obtained. 32,37) To be able to characterize grain morphology it is initially important to define what different grain morphologies are. To do this, it is important to consider defining a characteristic SDAS for each alloy for a given set of solidification Grain Morphology of As-Cast Wrought Aluminium Alloysconditions.…”

Section: Discussionmentioning

confidence: 99%

Grain Morphology of As-Cast Wrought Aluminium Alloys

2011

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Two of the most important microstructural features of alloys are the grain size and the secondary dendrite arm spacing (SDAS) and these two factors are shown to combine together to describe the grain morphology. Both grain refinement and the SDAS depend upon alloy composition through constitutional undercooling, but in different ways. It is shown that there is a 'characteristic' SDAS for each alloy at a particular cooling rate, and reducing the grain size causes the grain morphology to change from dendritic to cellular/rosette-like to globular or spherical. Increasing the cooling rate refines both the SDAS and the grain size, but reduces the SDAS more rapidly leading to finer, more dendritic grain structures. Particular ratios of grain size to SDAS are used to define each morphology and it is shown how these can assist with obtaining a required grain size and morphology through the use of solidification conditions and alloy chemistry.

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Section: Discussionmentioning

confidence: 99%

Grain Morphology of As-Cast Wrought Aluminium Alloys

2011

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“…Wang et al [143], have performed experiments with AlSi7Mg0.35 alloy with different pouring temperatures in a 50mm diameter mold. Using a stepped die for squeeze casting and reheating the produced billets from different pouring temperatures, they have shown that the low temperature poured material filled completely the die with negligible porosity (Figure 3.21).…”

Section: Liquidus or Low Superheat Castingmentioning

confidence: 99%

“…(a) (b) Figure 3.27: (a) Shape factor as a function of holding time, (b) average 3D particle diameter versus holding time [12] Wang et al [143][144][145] with experiments on A17SiO.35Mg in 50 mm steel mold and with different pouring temperatures, have shown that using both low pouring temperature and grain refining could optimize the structure during billet casting, partial remelting, and injecting. They confirmed that the addition of grain refiner imparts little effect on grain size for the casting condition used in their work but after isothermal holding at 580°C, they concluded that the grain refined samples attained a globular structure faster than the non grain refined alloy because of the more rosette like structure of the grain refined sample.…”

Section: Cmentioning

confidence: 99%

“…Isothermal held ~30seconds [154] 3.20 (a) Two different arrangements for tube and billet production by Osprey 98 process, (b) solidification mechanism of Osprey process [156] 3.21 Cast pieces from different pouring temperatures (above) and their X-ray 99 radiographs (below). Pouring temperatures are (a) 725°C, (b) 675°C, and (c) 650°C [143] 3.22 A comparison of semi-solid structures of: (a) B-refined billets, (b) TÍB2 100 grain refined (Reheat temperature: 585 °C) [159] 3.23 Schematic diagram for thixomolding process [8] 101 3.24 Grain refining of Al alloys with grain refiner containing Ti and B [9,160] [15] 3. 40 Microstructures of non-modified and modified A3 5 6 quenched billets [163] 116 3.41 Shear stress versus shear rate and viscosity versus shear rate curves for 117 different fluids [166] 3.42 Relation between apparent viscosity and shear rate in a logarithmic scale, 118 0.4wt% poly acrylamide in water, room temperature [168] 3.43 (a) Typical strain-time curves for equiaxed-dendritic structures, (b) relation 123 between initial pressure, morphology, and fraction solid [180] 3.44 (a) Stress vs. strain for specimens of different structures of Snl5%Pb, (b) 123 fraction of liquid vs. distance along the radius of a non-dendritic specimen (deformed at a strain rate of 1.33*10~V ) [179] 3.…”

Section: VImentioning

confidence: 99%

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Effects of grain refining and modification on the microstructural evolution of semi-solid 356 alloy /

Nafisi¹

2006

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Semi-solid metal (SSM) processing is gaming momentum as an effective alternative to the classical manufacturing processes of casting and forging. This category takes advantages of both liquid and solid forming processes. In the absence of shear force, semi-solid slug is similar to a solid, self standing, while with the application of shear force, the viscosity is reduced appreciably and the material flows like a liquid; Thixotropic-"

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“…One of the limitations of this route is the minimum size of billet that may be sprayed. In general this method could be more expensive if compared with agitation routes such as MHD; however, it may have particular advantages with high temperature alloys such as steels and superalloys.Liquidus pouring temperature or low pouring temperature is another low cost alternative route to generate structures [19][20][21][22][23][24][25][26]. The ability of low superheats to bring temperature gradient homogeneity within Semi solid slugs results in equiaxed grain growth instead of columnar growth.…”

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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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Semisolid Casting of AlSi7Mg0.35 Alloy Produced by Low-Temperature Pouring

Cited by 19 publications

References 0 publications

Grain Morphology of As-Cast Wrought Aluminium Alloys

Grain Morphology of As-Cast Wrought Aluminium Alloys

Effects of grain refining and modification on the microstructural evolution of semi-solid 356 alloy /

rheological behavior of semi-solid A356 alloy /

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