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

It was found that amorphous La55Al25Ni20 and La55Al25Cu20 alloys exhibit a distinct glass transition and the temperature span between Tg and Tx, ΔTx (= Tx - Tg) exceeds 50 K, as evidence of the formation of an amorphous phase with ΔTx above 50 K in a metal-metal type system. With the aim of obtaining further information on the glass transition behavior and the properties of supercooled liquid, the changes in fundamental properties of specific heat (Cp), viscosity (η), yield tensile strength (σy), tensile elongation including elastic elongation (εf) and viscoelasticity by glass-supercooled liquid transition 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 Cp by 12 J/mol. K and εf from 2.43 to 188% and a dramatic decrease of η to below 1012 Pa·s and σy 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 × 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 a typical glassy material.