GLASS-TRANSITION AND VISCOELASTIC BEHAVIORS OF LA55AL25NI20 AND LA55AL25CU20 AMORPHOUS-ALLOYS

It has been found that amorphous La55Al25Ni20 and La55Al25Cu20 alloys exhibit a distinct glass transition and the temperature span between T(g) and T(x), DELTA-T(x)(= T(x) - T(g)) exceeds 50 K. This is the first evidence for the formation of an amorphous phase with DELTA-T(x) above 50 K in a metal-metal type system. With the aim of clarifying the glass transition behavior and the properties of supercooled liquid in the metal-metal type amorphous alloys, the changes in fundamental properties of specific heat (C(p)), viscosity (eta), tensile yield strength (sigma-y), tensile elongation including elastic elongation (epsilon-f) and viscoelasticity in the glass transition region were examined for both amorphous alloys. The transition brought about significant changes in the above-described properties, i.e., for the La55Al25Ni20 alloy, an increase of C(p) by 12 J/mol.K and epsilon-f from 2.43 to 188% and a dramatic decrease of eta to below 10(12) Pa.s and sigma-y from 710 to 3.47 MPa. In addition, the complex modulus decreased from 33.5 to 1.79 GPa and the loss tangent increased rapidly from 9 x 10(-3) to 3.32. Similar significant changes in the fundamental properties were also observed for another La55Al25Cu20 amorphous alloy and hence these amorphous alloys were concluded to be typical glassy materials.