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Densification and characterization of nanocrystalline hypereutectic Al-Si-Fe-X alloy powder compacts produced by mechanical milling and field assisted sintering

Kandukuri Y. Sastry 1Ludo Froyen 1Jef Vleugels 1Omer Van der Biest 1Rolf Schattevoy 2Juergen Hennicke 3

1. K. U. Leuven, Department of Materials Science and Engineering (KUL, MTM), Kasteelpark Arenberg 44, Leuven 3001, Belgium
2. Powder Light Metals GmbH (PLM), Am Wiesenbusch 2, Gladbeck D-45966, Germany
3. FCT Systeme GmbH (FCT), Gewerbepark 11, Rauenstein D-96528, Germany


Rapidly solidified pre-alloyed Al-17Si-5Fe-3.5Cu-1.1Mg-0.6Zr (wt%) alloy powder was mechanically milled in air using stearic acid as process control agent. The resulting nanocrystalline powder was degassed at 350C for 5 hrs. Both as-milled and degassed powder were consolidated using field-assisted sintering (FAST) in steel dies under vacuum at 400C. Shrinkage along the pressure axis, temperature and electric current input were automatically stored through a data acquisition system.

As-milled powder and sintered compacts were characterized using optical microscopy, scanning electron microscopy (SEM), X-ray diffraction (XRD) and microhardness measurements. The crystal size, calculated from the line broadening of the X-ray diffraction peaks using Williamson-hall plots, of the FAST sintered mechanically alloyed materials was in the range of 53-70 nm, depending on the type and amount of process control agent used during milling and the FAST parameters. As-milled powders could not be densified to full theoretical density and the particle bonding was improper. Degassed powders on the other hand exhibited a very good interparticle cohesion and could be fully densified under identical sintering conditions.


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Presentation: oral at E-MRS Fall Meeting 2004, Symposium I, by Kandukuri Y. Sastry
See On-line Journal of E-MRS Fall Meeting 2004

Submitted: 2004-04-26 12:22
Revised:   2009-06-08 12:55