Refinement and densification of aluminum nickelides by severe plastic deformation

Two nickel (Ni)-coated aluminum (Al) powders were consolidated to full or near-full density by severe plastic deformation using the equal-channel angular extrusion (ECAE) technique. Mixtures of 78Al-22Ni at.% (63Al-37Ni wt.%) or 39Al-61Ni at.% (23Al-77Ni wt.%) were placed in square-shaped copper (Cu) or Ni casings, sealed, preheated to a range of temperatures from ambient to 700 degrees C, and, once at a uniform temperature, dropped into the ECAE die and single-pass extruded. It was found that the preheating temperature affected the transformation of the initial Al-Ni composition into aluminum nickelide (Al-Ni) intermetallics. It was also found that the use of the nickel can significantly affect the densification of the powders. Scanning electron microscopy, energy dispersive x-ray spectroscopy, x-ray diffraction and microhardness measurements were used to examine the nature of the resultant intermetallics. The onset and nature of the transformation from the precursors into the products were further studied by differential thermal analysis. These results and the role of ECAE on the transformation are discussed.