Glass transition and visco-elastic behavior of new amorphous light-metal alloys in Al- and Mg-based systems

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1. The change in the supercooled liquid region for Mg_<65>Cu_<25>Ln_<10>(Ln=Y, La, Ce, Nd, Sm, Tb or Gd) amorphous alloys with Ln elements was systematically examined and the Mg_<65>Cu_<25>Tb_<10> amorphous alloy was found to have a wide supercooled liquid region (*Tx) reaching 75K.2. We succeeded in producing a bulky Mg_<65>Cu_<25>Tb_<10> alloy by a metallic mold casting process. The viscosity of the amorphous bulk decreases rapidlyin the temperature range above Tg and is as low as 10^7 Pa・s at a temperature just below Tx.3. We searched a new amorphous alloy exhibiting a further wide supercooled liquid region and found that Zr=Al-TM amorphous alloys have a wide supercooled liquid region before crystalization. The largest *Tx value attained is 127K for Zr_<65>Al_<7.5>Ni_<10>Cu_<17.5>.4. We also succeeded in producing an amorphous phase in Gd-Al-Ni system containing a ferromagnetic Gd element as a major component. The glass transition was observed in the composition range of 10 to 35%Ni and 10 to 35% Al and the largest *Tx was 65K for Gd_<55>Al_<25>Ni_<20>.5. The dynamical mechanical properties were examined for La_<55>Al_<25>Ni_<20> amorphous alloys and the loss modulus E"(T) was found to show two distinguishable peaks consisting of a main peak at 509K and a subpeak at 491K.Furthermore, the storage modulus E'(T) and the E"(T) as a function of frequency were examined. As the frequency decreases, the main peak in the E"(T) curve shifts to a lower temperature side, leading to the appearance of two-distinguishable peaks. It is therefore concluded that the relaxation in the glass transition and supercooled liquid region occurs through two different relaxation processes.