A mechanism for the poisoning effect of silicon on the grain refinement of Al–Si alloys

Qiu, Dong; Taylor, J. A.; Zhang, Mingxing; Kelly, P.M.

doi:10.1016/j.actamat.2006.09.046

Cited by 212 publications

(106 citation statements)

References 16 publications

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“…Si in the melt reacted with Ti to form Ti-Si compounds, and the TiB 2 particles that act as heterogeneous nucleation sites for primary a-Al phase could be poisoned by Si by coating the surfaces with Ti-Si compounds [16,17]. The detail poisoning mechanism of Si on TiB 2 particles has been verified by experiment recently with Al-Si-Ti particles observed on the prism face of TiB 2 [18].…”

Section: Discussionmentioning

confidence: 77%

“…The Al5Ti1B master alloy offers good performance in the casting of wrought alloys, but it is hard to meet the expectations in cast Al-Si alloys, especially with a content of Si higher than 3.5 wt% [13][14][15]. The reason is that Si in the melt reacts with Ti to form Ti-Si phases, which poison the TiB 2 nucleation site [16,17]. The poisoning mechanism of Si on the TiB 2 nucleation sites has been verified by experiment recently, and Al-Si-Ti particles were observed on the prism face of TiB 2 particles [18].…”

Section: Introductionmentioning

confidence: 99%

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Si poisoning and promotion on the microstructure and mechanical properties of Al–Si–Mg cast alloys

Dong

2018

J Mater Sci

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Hypoeutectic Al-xSi-0.45Mg (x = 6.5, 7.5, 8.5, 9.5) alloys were refined by Al5Ti1B containing TiB 2 and Al3Ti3B containing TiB 2 and AlB 2 , respectively. With increasing Si, Si poisoning on TiB 2 results in the obvious coarsening of primary a-Al in Al5Ti1B-refined alloys from 350 ± 40 to 400 ± 50, 475 ± 50 and 560 ± 80 lm, and the competition between Si promotion on AlB 2 and Si poisoning on TiB 2 leads to the slight coarsening of primary a-Al in Al3Ti3B-refined alloys from 215 ± 30 to 265 ± 35, 265 ± 30 and 315 ± 25 lm. After T6 heat treatment, with increasing Si, the yield strength (YS) of Al5Ti1B-refined alloys increases from 294 ± 2 to 299 ± 2, 304 ± 1 and 309 ± 2 MPa, and the elongation first increases from 3.5 ± 0.8 to 4.5 ± 1.0 and 7.8 ± 1.4%, after decreases to 5.5 ± 1.2%, while the YS of the Al3Ti3B-refined alloys increases from 300 ± 1 to 305 ± 2, 312 ± 1 and 317 ± 2 MPa, and the elongation increases from 6.1 ± 1.1 to 8.5 ± 1.2, 11.8 ± 1.5 and 12.1 ± 1.6%. The increase in the secondary phase and precipitation strengthening results in the increase in strength with increasing Si. With increasing Si, the decrease in porosity formation by decreasing solidification interval and increasing fluidity is superior to the increase in porosity formation by slightly coarsening grain size, which leads to the increase in ductility in the Al3Ti3B-refined alloys, while the competition between porosity decreasing and increasing factors leads to the inverted 'V'-shaped evolution of ductility in the Al5Ti1B-refined alloys.

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Section: Discussionmentioning

confidence: 77%

Section: Introductionmentioning

confidence: 99%

Si poisoning and promotion on the microstructure and mechanical properties of Al–Si–Mg cast alloys

Dong

2018

J Mater Sci

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“…This is the so-called poisoning effect on grain refinement. [4][5][6][7][8][9] In Al-Si cast alloys, when the Si content exceeds~2 wt pct, a poisoning effect is observed and it becomes worse with increased Si content. When Si content is greater than 3 wt pct, the grain refining efficiency of commercial Al-Ti-B master alloys is poor.…”

Section: Introductionmentioning

confidence: 99%

“…When Si content is greater than 3 wt pct, the grain refining efficiency of commercial Al-Ti-B master alloys is poor. [4][5][6][7][8][9] With the increase in billet size and resulting increase in solidification time, equiaxed grain settling becomes more important in determining the columnar to equiaxed transition (CET) and, therefore, grain refinement. This makes the achieving grain refinement even more challenging.…”

Section: Introductionmentioning

confidence: 99%

Grain Refinement and Improvement of Solidification Defects in Direct-Chill Cast Billets of A4032 Alloy by Melt Conditioning

Zhao

Yang

et al. 2017

Metall Mater Trans B

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Melt-conditioned, direct-chill (MC-DC) casting is an emerging technology to manipulate the solidification process by melt conditioning via intensive shearing in the sump during DC casting to tailor the solidification microstructure and defect formation. When using MC-DC casting technology in an industrial scale DC cast billet of an A4032 aluminum alloy, significant grain refinement and uniform microstructure can be achieved in the primary a-Al phase with fine secondary dendritic arm spacing (SDAS). Improved macrosegregation is quantitatively characterized and correlated with the suppression of channel segregation. The mechanisms for the prevention of channel segregation are attributed to the increased local cooling rate in the liquid-solid phase region in the sump and the formation of fine equiaxed dendritic grains under intensive melt shearing during MC-DC casting. A critical cooling rate has been identified to be around 0.5 to 1 K/s (°C/s) for the channel segregation to happen in the investigated alloy based on quantitative metallographic results of SDAS. Reduction and refinement of microporosity is attributed to the improved permeability in the liquid-solid phase region estimated by the Kozeny-Carman relationship. The potential improvement in the mechanical properties achievable in MC-DC cast billets is indicated by the finer and more uniform forging streamline in the forgings of MC-DC cast billet.

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“…The grain refiner tool is mentioned as an important technological resource to obtain a homogeneous and refined microstructure in casted plates. It consists to obtain fine and axial grains through the controlled addition of inoculants in the liquid metal, favoring the heterogeneous nucleation mechanism [15][16][17][18][19] . According to Easton and Stjohn 14 , the type of inoculant often used for aluminum alloys are based on the addition of Al, Ti and B.…”

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confidence: 99%

The Effect of Casting Speed and the Fraction of Al5%Ti1%B Inoculant on the Microstructure and Mechanical Properties of the AA5052 Aluminum Alloy Produced by the Direct Chill Process

Faria

Leite

2018

Mat. Res.

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This study aimed to assess the effect of casting speed and the addition of Al5%Ti1%B inoculant in the casted AA5052 aluminum alloy plate manufactured by the Direct Chill process. The focus of this work was to decrease the rejection index of rolled products due to the occurrence of superficial flaws on plates. These defects impact directly on the production costs and on the rolled product quality. The main cause of those flaws is associated with the billet porosity that is related with the excess of atomic hydrogen incorporated into the metallic bath and with the metal shrinkage during solidification. Four different cast conditions were industrially tested, combining two casting speeds and two inoculants amounts. The effect of those variables on the alloy mechanical properties and on their performance in rolling process was also assessed. It was observed that the higher the casting speed and the inoculant fraction, the more refined the microstructure and the lower the fraction and diameter of formed micropores. The increase of casting speed and the inoculant fraction improved the AA5052 alloy rolling performance. The application of these results in an industrial scale performed a decrease from 5.03% to 0.39% per month in the rejection index of rolled products.

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A mechanism for the poisoning effect of silicon on the grain refinement of Al–Si alloys

Cited by 212 publications

References 16 publications

Si poisoning and promotion on the microstructure and mechanical properties of Al–Si–Mg cast alloys

Si poisoning and promotion on the microstructure and mechanical properties of Al–Si–Mg cast alloys

Grain Refinement and Improvement of Solidification Defects in Direct-Chill Cast Billets of A4032 Alloy by Melt Conditioning

The Effect of Casting Speed and the Fraction of Al5%Ti1%B Inoculant on the Microstructure and Mechanical Properties of the AA5052 Aluminum Alloy Produced by the Direct Chill Process

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