Al-La-Ni-Fe Amorphous Alloys and Amorphous-crystalline Composites Produced by Mechanical Alloying

摘要

Al-La-Ni-Fe alloys of three different compositions (Al_(82)La_(10)Ni_4Fe_4, Al_(85)La_9Ni_3Fe_3 and Al_(88)La_6Ni_3Fe_3) were prepared high-energy milling in a planetary ball-mill (AGO-2). Complete amorphization was observed for the Al_(82)La_(10)Ni_4Fe_4 alloy after milling for 350 h at a rotational speed of 300 rpm. In contrast, the Al_(85)La_9Ni_3Fe_3 and Al_(88)La_6Ni_3Fe_3 powders contained the FCC Al phase even for prolonged milling. The amorphization tendency was found to increase in the order of Al_(88)La_6Ni_3Fe_3 < Al_(85)La_9Ni_3Fe_3 < Al_(82)La_(10)Ni_4Fe_4, which may well be ascribed to the increasing atomic size mismatch of the constituent elements on La addition. DSC analyses of amorphous samples revealed two-stage crystallization processes for all three alloys, however, with strong variations in the thermal stability upon compositional changes. As observed by SEM, amorphous powders consisted of particles with nearly spherical shape and diameters ranging from 5 to 20 μm.