Al-La-Ni-Fe bulk metallic glasses produced by mechanical alloying and spark-plasma sintering

Abstract

High-energy ball-milling in hexane medium was employed to prepare amorphous Al-La-Fe-Ni alloys of three different nominal compositions (Al82La10Ni4Fe4, Al85La9Ni3Fe3 and Al88La6Ni3Fe3, numbers indicate at.%). Using a planetary ball-mill (AGO-2) at a rotational speed of 300 rpm, nearly complete amorphization could be achieved for the Al82La10Ni4Fe4 alloy after milling for 350 h. In contrast, the Al85La9Ni3Fe3 and Al88La6Ni3Fe3 samples remained crystalline to a certain extent even after prolonged milling and contained FCC Al crystallites. The glass forming ability was found to increase with decreasing Al and increasing La content, which can be ascribed to the enhanced atomic size mismatch of the constituents on La addition. Amorphous Al82La10Ni4Fe4 powder undergoes two-stage crystallization with onset temperatures at 640 and 700 K and glass transition at 566 K. Differences to DSC traces of previously studied melt-spun samples are believed to be mainly due to carbon impurity incorporation and compositional changes during milling. Taking into account the DSC data, consolidation of amorphous Al82La10Ni4Fe4 powder was attempted by means of spark-plasma sintering at a temperature of 613 K and applied pressures of 400 and 600 MPa. Compacts produced under these conditions were found to have relative densities of 80% and 96%, respectively. (c) 2006 Elsevier B.V. All rights reserved.