Effect of primary crystals on pore morphology during semi-solid foaming of A2024 alloys

Takashi Kuwahara*, Mizuki Saito, Taro Osaka, Shinsuke Suzuki

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

5 Citations (Scopus)

Abstract

We investigated pore formation in aluminum foams by controlling primary crystal morphology using three master alloys. The first one was a direct chill cast A2024 (Al-Cu-Mg) alloy (DC-cast alloy). The others were A2024 alloys prepared to possess fine spherical primary crystals. The second alloy was made by applying compressive strain through a Strain-Induced Melt-Activated process alloy (SIMA alloy). The third one was a slope-cast A2024 alloy (slope-cast alloy). Each alloy was heated to either 635C (fraction of solid fs = 20%) or 630C (fs = 40%). TiH2 powder was added to the alloys as a foaming agent upon heating them to a semi-solid state and they were stirred while being held in the furnace. Subsequently, A2024 alloy foams were obtained via water-cooling. The primary crystals of the DC-cast alloy were coarse and irregular before foaming. After foaming, the size of the primary crystals remained irregular, but also became spherical. The SIMA and slope-cast alloys possessed fine spherical primary crystals before and after foaming. In addition to average-sized pores (macro-pores), small pores were observed inside the cell walls (micro-pores) of each alloy. The formation of macro-pores did not depend on the formation of the primary crystals. Only in the DC-cast alloy did fine micro-pores exist within the primary crystals. The number of micro-pores in the SIMA and slope-cast alloys was one third of that in the DC-cast alloy.

Original languageEnglish
Article number88
JournalMetals
Volume9
Issue number1
DOIs
Publication statusPublished - 2019 Jan 1

Keywords

  • Aluminum foam
  • Pore morphology
  • Primary crystals
  • SIMA process
  • Semi-solid
  • Slope casting

ASJC Scopus subject areas

  • Materials Science(all)

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