Pressure effects on Al89La6Ni5 amorphous alloy crystallization

The pressure effect on the crystallization of the Al89La6Ni5 amorphous allo y has been investigated by in situ high-pressure and high-temperature x-ray powder diffraction using synchrotron radiation. The amorphous alloy crysta llizes in two steps in the pressure range studied (0-4 GPa). The first proc ess, corresponding to simultaneous precipitation of fcc-Al crystals and the metastable bcc-(AlNi)(11)La-3-like phase, is governed by a eutectic reacti on. The second process corresponds to the transformation of a residual amor phous alloy into fcc-Al, Al11La3, Al3Ni, and as yet unidentified phase(s). The applied pressure strongly affects the crystallization processes of the amorphous alloy. Both temperatures first decrease with pressure in the pres sure range of 0-1 GPa and then increase with pressure up to 4 GPa. The resu lts are discussed with reference to competing processes between the thermod ynamic potential barrier and the diffusion activation energy under pressure . (C) 2000 American Institute of Physics. [S0003- 6951(00)00951-7].