Characterization investigations of melt-spun ternary Al-xSi-3.3Fe (x=10, 20 wt.%) alloys

Two ternary Al-xSi-3.3Fe alloys, one with the hypoeutectic (x=10 wt.% Si) and the other with the hypereutectic (x=20 wt.% Si) composition were rapidly quenched from the melt at cooling rates between 10(6) and 10(7) K/s using the melt-spinning technique. The resulting melt-spun ribbons were characterized using optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) and microhardness techniques. On the basis of the Al peak shifts measured in the XRD scans, solid solubility extension values of 3.01 and 2.97 at.% Si in Al were determined for the hypoeutectic and hypereutectic alloy, respectively. Whereas SEM investigations showed the presence of dendrites rich in Al, TEM investigations revealed nanosized spherically-shaped Si crystals 5-10 nm in size in the hypoeutectic alloy and those equiaxed in shape having a size range between 50 and 70 nm. Both XRD and TEM investigations confirmed the absence of any intermetallic phase formation for both alloys. The microhardness values of the hypoeutectic and hypereutectic ternary Al-Si-Fe alloys were measured as 251 and 297 kg/mm(2), respectively. (C) 2001 Elsevier Science B.V. All rights reserved.