FORMATION, THERMAL-STABILITY AND MECHANICAL-PROPERTIES OF AMORPHOUS-ALLOYS IN THE MG TRANSITION-METAL (NI, CU) ALKALINE-EARTH METAL (CA, SR, BA) SYSTEM

Mg-Ni-Ca, Mg-Ni Sr, Mg-Ni-Ba and Mg-Cu-Ca alloys were found to be amorphized by melt-spinning in the compositional ranges 0 to 30% Ni and O to 40% Ca, 5 to 20% Ni and 0 to 15% Sr, 10 to 25% Ni and 0 to 15% Ba, and 0 to 50% Cu and 0 to 35% Ca, respectively. In the amorphous Mg-Ni-Ca and Mg-Cu-Ca alloys, the glass transition was observed in the ranges of 7.5 to 15% Ni and 2.5 to 5% Ca and 10 to 40% Cu and 2.5 to 7.5% Ca, respectively. The crystallization temperature (T(x)) of amorphous Mg-Cu-Ca alloys increases with increasing Cu content, while T(x) for amorphous Mg-Ni-Ca and Mg-Ni-Sr alloys shows a maximum value of 459 and 471 K, respectively, at 15% Ni. The glass transition temperature (T(g)) increases monotonously with increasing Ni or Cu content. Amorphous Mg-Ni-Ca and Mg-Ni-Sr ribbons containing more than 80% Mg have a good bending ductility and the highest tensile fracture strength (sigma(f)) reaches 690 and 680 M Pa, respectively. The ratios of sigma(f) to density are nearly equal to those for previously reported Mg-Ni-(Y or Ln) amorphous alloys with higher sigma(f) values because of the low densities of the present Mg-based alloys.