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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