Crystallisation in Al–ETM–LTM–La metallic glasses

The addition of early and late transition metals to Al–La alloys has a strong influence on the glass forming ability and the subsequent devitrification route. Four quaternary alloys of nominal composition Al87Fe5Ni5La3, Al88Fe3Ni3La6, Al82Fe4Ni4La10, Al75Ti10Ni10La5 and a ternary alloy of nominal composition Al75Ti10Ni15 have been melt spun at 10, 20, 30 and 40 m s−1 wheel speed. Amorphous alloys thus secured have been annealed at the peak temperatures as indicated by the DSC thermograms from 10 min to 2 h. The Al87Fe5Ni5La3 alloy showed in the melt-spun state precipitates of α-Al, a FCC phase with 12.5 Å lattice parameter. The Al88Fe3Ni3La6 alloy in the melt-spun state shows nano-sized precipitate of α-Al in the amorphous matrix. The Al82Fe4Ni4La10 alloy after melt-spinning at 40, 30, 20 m s−1 wheel speed becomes amorphous and shows precipitates of α-Al in the amorphous matrix when melt spun at 10 m s−1 wheel speed. The amorphous phase in the Al82Fe4Ni4La10 alloy is stable up to 625 K and crystallises in three exothermic heat events. After heat treatment at the first crystallisation peak temperature and below the first crystallisation temperature precipitation of α-Al in the amorphous matrix can be observed. At the end of the crystallisation process very fine precipitates of Al3La and LaNi can be seen at the α-Al grain boundaries. Activation energy of crystallisation has been calculated by Kissinger and Ozawa method. Al–Ti–Ni–La becomes partially amorphous after melt-spinning. Al–Ti–Ni alloy does not produce amorphous phase after melt-spinning. Precipitation of Al3Ti phase can be observed in both the alloys. The development of different microstructures, effect of La on the glass forming ability and the stabilisation of the glassy matrix with enrichment of La and with the progress of crystallisation, establishes a possible link between Al based metallic glasses and La based bulk metallic glasses.