The impact of melt retention time on the strontium modification efficiency

Scientific paper - Original scientific paper

• Author: Franjo Kozina
• Author: Zdenka Zovko Brodarac
• Author: Barbara Tubić Bulat
• Editor: Sonja Jozić
• Editor: Branimir Lela
• Editor: Nikola Gjeldum
• Author's institution: University of Zagreb; Faculty of Metallurgy; (Department of Process Metallurgy); (Laboratory of Iron, Steel and Founding)
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Metallurgy; Process Metallurgy

Abstract (english)

The modification of eutectic (αAl+βSi) phase is frequently
performed during processing of aluminum-silicone (Al-Si) based foundry
alloys leading to a structural transformation of the eutectic βSi phase from a
course plate to a fine fibrous morphology. The morphological refinement
of the brittle eutectic βSi phase improves ductility, tensile strength, and
elongation. This research was performed to estimate the influence of melt
retention time on strontium (Sr) modification efficiency. For this purpose,
the AlSi12 alloy with eutectic composition was produced and processed by
the addition of AlSr10 master alloy. The samples for chemical, mechanical
and microstructure analysis were taken with melt retention time of 20 min,
40 min and 80 min. The results of chemical composition analysis indicated
the decrease in Sr content with the increase in melt retention time. The poor
Sr recovery was a result of the subsequent addition of chemical degassing
agents led to the gas entrapment in the melt. Consequently, the highest gas
index and most severe porosities were found in sample with retention time
of 20 min. The fully modified eutectic (αAl+βSi) phase morphology was only
obtained in sample with retention time of 20 min. After melt retention time
of 40 min the unmodified plate-like eutectic βSi phase particles were found.
Additional prolongation of melt retention time to 80 min led to the
coarsening of eutectic βSi phase particle. The plate-like eutectic βSi phase
particles were located near the primary αAl dendritic network and
surrounding the primary βSi phase particles. This phase distribution
suggests that the transformation of the primary αAl dendritic network is
followed by solidification of unmodified eutectic βSi phase particles.

• Keywords (english): AlSi12 alloy; Strontium; Eutectic modification; Modification efficiency
• Language: english
• Publication type: Scientific paper - Original scientific paper
• Publication status: Published
• Peer review: Peer review - international
• Publication version: Published version
• Publication title: CONFERENCE PROCEEDINGS MECHANICAL TECHNOLOGIES AND STRUCTURAL MATERIALS
• Numbering: pp. 69-73
• p-ISSN: 1847-7917
• URN:NBN: urn:nbn:hr:115:110920
• Publication: 2021
• Conference: Title: 10 International Conference Mechanical Technologies and Structural Materials 2021; Acronym: MTSM 2021; Location: Split, Croatia; Organizer: Hrvatsko društvo za strojarske tehnologije; Start date: 2021-09-09; End date: 2021-09-24; Assembly type: Lecture
• Document URL: http://www.strojarska-tehnologija.hr/#mtsm
• Type of resource: Text
• Publisher: Hrvatsko društvo za strojarske tehnologije
• Publishing place: Split
• Access conditions: Open access
• Created on: 2021-10-01 07:55:49