Effect of conditions of unidirectional solidification on microstructure and pore morphology of Al-Mg-Si alloys

Tae Bum Kim, Shinsuke Suzuki, Hideo Nakajima

Research output: Contribution to journalArticle

6 Citations (Scopus)

Abstract

Aluminum and Al-Mg-Si alloy ingots with pores were fabricated by unidirectional solidification through thermal decomposition of Ca(OH) 2 powders. The porosity of aluminum and Al-Mg-Si alloy were 10-17% and 0.1-2%, respectively. While the pores with 250-400 μm diameter were observed in a grain or across several grains in the aluminum ingots, smaller pores with 50-300 μm were observed in an eutectic region between primary α dendrites in the Al-Mg-Si ingots. In the alloys with Mg(0.25-0.5 mass%) and Si(0.2-0.4 mass%), the unidirectional pores were aligned between columnar dendrites grown in the unidirectional solidification. With higher Mg and Si contents, the equiaxed dendrite zones widi spherical pores were observed in a region with low temperature gradient. The results of thermal analysis showed that constitutional supercooling, which causes equiaxed dendrites, tends to occur with increase in Mg and Si contents and with low temperature gradient at the solid-liquid interface. Under this condition, spherical pores were evolved, because the surrounding or-dendrites solidified isotropicallv. Therefore, it is concluded that the pore growth direction is affected by morphology of dendrites.

Original languageEnglish
Pages (from-to)496-502
Number of pages7
JournalMaterials Transactions
Volume51
Issue number3
DOIs
Publication statusPublished - 2010 Mar
Externally publishedYes

Fingerprint

Ingots
Aluminum
solidification
Solidification
Dendrites (metallography)
dendrites
porosity
Thermal gradients
microstructure
Microstructure
Supercooling
ingots
Powders
Eutectics
Thermoanalysis
Pyrolysis
Porosity
aluminum
temperature gradients
Liquids

Keywords

  • A6061
  • Aluminum-magnesium-silicon alloy
  • Columnar dendrite
  • Equiaxed dendrite
  • Porous aluminum
  • Unidirectional solidification

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanical Engineering
  • Mechanics of Materials

Cite this

Effect of conditions of unidirectional solidification on microstructure and pore morphology of Al-Mg-Si alloys. / Kim, Tae Bum; Suzuki, Shinsuke; Nakajima, Hideo.

In: Materials Transactions, Vol. 51, No. 3, 03.2010, p. 496-502.

Research output: Contribution to journalArticle

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abstract = "Aluminum and Al-Mg-Si alloy ingots with pores were fabricated by unidirectional solidification through thermal decomposition of Ca(OH) 2 powders. The porosity of aluminum and Al-Mg-Si alloy were 10-17{\%} and 0.1-2{\%}, respectively. While the pores with 250-400 μm diameter were observed in a grain or across several grains in the aluminum ingots, smaller pores with 50-300 μm were observed in an eutectic region between primary α dendrites in the Al-Mg-Si ingots. In the alloys with Mg(0.25-0.5 mass{\%}) and Si(0.2-0.4 mass{\%}), the unidirectional pores were aligned between columnar dendrites grown in the unidirectional solidification. With higher Mg and Si contents, the equiaxed dendrite zones widi spherical pores were observed in a region with low temperature gradient. The results of thermal analysis showed that constitutional supercooling, which causes equiaxed dendrites, tends to occur with increase in Mg and Si contents and with low temperature gradient at the solid-liquid interface. Under this condition, spherical pores were evolved, because the surrounding or-dendrites solidified isotropicallv. Therefore, it is concluded that the pore growth direction is affected by morphology of dendrites.",
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AB - Aluminum and Al-Mg-Si alloy ingots with pores were fabricated by unidirectional solidification through thermal decomposition of Ca(OH) 2 powders. The porosity of aluminum and Al-Mg-Si alloy were 10-17% and 0.1-2%, respectively. While the pores with 250-400 μm diameter were observed in a grain or across several grains in the aluminum ingots, smaller pores with 50-300 μm were observed in an eutectic region between primary α dendrites in the Al-Mg-Si ingots. In the alloys with Mg(0.25-0.5 mass%) and Si(0.2-0.4 mass%), the unidirectional pores were aligned between columnar dendrites grown in the unidirectional solidification. With higher Mg and Si contents, the equiaxed dendrite zones widi spherical pores were observed in a region with low temperature gradient. The results of thermal analysis showed that constitutional supercooling, which causes equiaxed dendrites, tends to occur with increase in Mg and Si contents and with low temperature gradient at the solid-liquid interface. Under this condition, spherical pores were evolved, because the surrounding or-dendrites solidified isotropicallv. Therefore, it is concluded that the pore growth direction is affected by morphology of dendrites.

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