Effect of microstructure on pore morphology in Al-Mg-Si alloys fabricated by unidirectional solidification

Tae Bum Kim, Shinsuke Suzuki, Hideo Nakajma

Research output: Contribution to journalArticle

Abstract

Aluminum and Al-Mg-Si alloys ingots with pores were fabricated by unidirectional solidification through thermal decomposition of Ca(OH) 2 powders. The porosity of aluminum and Al-Mg-Si alloys is 10-17% and 0.1-2%, respectively. While pores with 250-400 μm in diameter were observed in a grain or across several grains in the aluminum ingot, 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 (0.2-0.4mass%), the directional pores are aligned between columnar dendrites grown in the unidirectional solidification. With higher Mg and Si contents, the equiaxed dendrite zone with spherical pores were observed in a region with a low temperature gradient. The results of thermal analyses showed that constitutional supercooling tends to occur with increase in Mg and Si contents and with a low temperature gradient at the solid-liquid interface, and thus spherical pores are evolved. Thus, it is concluded that the pore growth direction has a strong relation with the direction of dendrites.

Original languageEnglish
Pages (from-to)678-684
Number of pages7
JournalKeikinzoku/Journal of Japan Institute of Light Metals
Volume59
Issue number12
DOIs
Publication statusPublished - 2009 Dec

Keywords

  • A6061
  • Al-Mg-Si alloy
  • Columnar dendrite
  • Equiaxed dendrite
  • Porous aluminum
  • Unidirectional solidification

ASJC Scopus subject areas

  • Mechanics of Materials
  • Mechanical Engineering
  • Metals and Alloys
  • Materials Chemistry

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