Al3Ni2-Al composites with nanocrystalline intermetallic matrix produced by consolidation of milled powders

Mechanically alloyed nanocrystalline Al63Ni37 powder with a metastable structure of NiAl phase was mixed with 20, 30 and 40 vol.% of Al powder. The powder mixtures as well as pure powder of Al63Ni37 alloy were consolidated at 600 degrees C under the pressure of 7.7 GPa. The bulk materials were characterised by structural investigations (X-ray diffraction, light and scanning electron microscopy, energy dispersive spectroscopy), compression and hardness tests and measurements of density and open porosity. During the consolidation, the metastable NiAl phase transformed into the equilibrium Al3Ni2 intermetallic. The mean crystallite size of the Al3Ni2 intermetallic in the bulk materials is below 40 nm. The microstructure of the composite samples consists of Al3Ni2 intermetallic areas surrounded by lamellae-like Al regions. The hardness of the produced Al3Ni2-Al composites is in the range of 5-6.5 GPa (514-663 HV1), while that of the Al3Ni2 intermetallic is 9.18 GPa (936 HV1). The compressive strength of the composites increases with the decrease of Al content, ranging from 567 MPa to 876 MPa. The plastic elongation of the composites was increasing with the increase of Al content, while the Al3Ni2 intermetallic failed in the elastic region. (C) 2014 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.