Effect of Iron on Microstructure of Al-12Si-1Cu-0.1Mg Alloy

Abstract

Iron is generally considered harmful as an element in Al foundry alloys due to its adverse effect on the mechanical properties, and the same is attributed to formation of brittle Fe-rich intermetallic compounds formed with combination of different alloying elements present in the alloy, e.g., Al₅FeSi (β phase). The present article describes the results of an experimental work to study the effect of Fe on microstructure and hardness of Al-12Si-1Cu-0.1Mg alloy. Microstructure characterization was performed by using image analyzer, scanning electron microscope (SEM), and electron probe microanalysis (EPMA). It was found that increase in wt% of Fe leads to significant increase in area fraction and aspect ratio of Fe-rich intermetallics and decrease in Al–Si eutectic area fraction. Hardness remains steady up to 0.6 wt% Fe at 86 Hv, and increases significantly afterwards to 105 Hv. Secondary as well as Primary dendritic arms spacing reduces significantly with an increase in Fe content. Increase in porosity was observed above 0.6 wt% Fe.

Keywords:

• α-Al
• Al–Si alloy
• Al–Si eutectic
• Area Fraction
• EPMA
• Fe-rich intermetallics
• Grain refining
• Hardness
• Iron
• Metallography
• Mold casting
• Porosity
• Primary Dendritic Arm Spacing (PDAS)
• Secondary Dendritic Arm Spacing (SDAS)
• SEM

ACKNOWLEDGMENT

Financial assistance from Council for Scientific and Industrial Research (CSIR), New Delhi for project “Development of Wear Resistant Piston Materials” vide sanction no. 22(0382)/05/EMR/-II dated 13.07.2005 is gratefully acknowledged.