Mechanical properties and microstructures of Al-Fe alloys processed by high-pressure torsion

Al-Fe alloys in the form of thin disks 10 mm in diameter, with Fe nominal weight fractions of 0.5, 1, 2, and 5 pct, were extracted from bulk-extruded rods and processed by high-pressure torsion (HPT). A group of these bulk samples was processed in an as-received state, whereas another group was annealed at 773 K (500 °C) for a period of 1 hour, prior to the application of HPT. An additional set of samples was prepared by mixing high-purity powders with similar Fe contents and consolidated directly in the HPT facility. The samples were processed up to 10 revolutions. Vickers microhardness, tensile strength, and elongation to failure were evaluated for all cases along with observations of the Al matrix by transmission electron microscopy (TEM). Basic characterization of the microstructures was carried out by X-ray diffraction (XRD) and optical microscopy (OM). Significant strengthening with ductility retained was achieved in the bulk samples as a consequence of grain refinement and dispersion of intermetallic phases. Powder samples had a more gradual increase in strength but increased ductility as a result of the imposed strain.