Effect of rapid solidification on the microstructure and mechanical properties of hot-pressed Al-20Si-5Fe alloys

Journal Article · Sun Nov 15 04:00:00 EST 2009 · Materials Characterization

DOI:https://doi.org/10.1016/J.MATCHAR.2009.06.014· OSTI ID:22066144

Rajabi, M; Vahidi, M ^[1]; Simchi, A ^[1]; Davami, P ^[1]

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1. Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of)

The aim of this work is to study the effect of cooling rate and subsequent hot consolidation on the microstructural features and mechanical strength of Al-20Si-5Fe-2X (X = Cu, Ni and Cr) alloys. Powder and ribbons were produced by gas atomization and melt spinning processes at two different cooling rates of 1 x 10{sup 5} K/s and 5 x 10{sup 7} K/s. The microstructure of the products was examined using optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. The particles were consolidated by hot pressing at 400 deg. C/250 MPa/1 h under a high purity argon atmosphere and the microstructure, hardness and compressive strength of the compacts were evaluated. Results showed a profound effect of the cooling rate, consolidation stage, and transition metals on the microstructure and mechanical strength of Al-20Si-5Fe alloys. While microstructural refining was obtained at both cooling rates, the microstructure of the atomized powder exhibited the formation of fine primary silicon ({approx} 1 {mu}m), eutectic Al-Si phase with eutectic spacing of {approx} 300 nm, and {delta}-iron intermetallic. Supersaturated Al matrix containing 5-7 at.% silicon and nanometric Si precipitates (20-40 nm) were determined in the microstructure of the melt-spun ribbons. The hot consolidation resulted in coarsening of Si particles in the atomized particles, and precipitation of Si and Fe-containing intermetallics from the supersaturated Al matrix in the ribbons. The consolidated ribbons exhibited higher mechanical strength compared to the atomized powders, particularly at elevated temperatures. The positive influence of the transition metals on the thermal stability of the Al-20Si-5Fe alloy was noticed, particularly in the Ni-containing alloy.

• OSTI ID: 22066144
• Journal Information: Materials Characterization, Journal Name: Materials Characterization Journal Issue: 11 Vol. 60; ISSN 1044-5803; ISSN MACHEX
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
77 NANOSCIENCE AND NANOTECHNOLOGY
ALUMINIUM BASE ALLOYS
COMPRESSION STRENGTH
COOLING
HARDNESS
HOT PRESSING
INTERMETALLIC COMPOUNDS
IRON-DELTA
MATRIX MATERIALS
MICROSTRUCTURE
NANOSTRUCTURES
OPTICAL MICROSCOPY
PHASE STABILITY
POWDERS
PRECIPITATION
SCANNING ELECTRON MICROSCOPY
SILICON
SOLIDIFICATION
TRANSMISSION ELECTRON MICROSCOPY
X-RAY DIFFRACTION