2 GLASS TRANSITIONS IN MECHANICAL RELAXATION OF A LA55AL25NI20 AMORPHOUS ALLOY

Dynamic mechanical properties of a La55Al25Ni20 amorphous alloy reveal two relaxation processes in the glass transition region. At a frequency of 62.8 rad/s the loss modulus, E", shows two peaks at about 483 and 507 K. With decreasing frequency, the peak temperatures shift lower and the two peaks tend to separate further. Frequency scans also show a main peak at lower frequency and a lower peak at higher frequency as a shoulder. Using the time-temperature superposition process, a master curve of loss modulus has been constructed. Activation energies were calculated from the shift factor and found to be 400 and 550 kJ/mol, respectively, for the higher frequency and lower frequency peak. The occurrence of the two relaxations is associated with spinodal phase separation.