This paper deals with the first success of producing a bulk Zr-Al-Ni-Cu glassy alloy with the same mechanical properties as those for the as-cast bulky and melt-spun glassy alloys by extrusion of atomized glassy powder in the supercooled liquid region. A Zr65Al10Ni10Cu15 glassy alloy was chosen as the best composition because of the achievement of the lowest viscosity in the supercooled liquid region and an appropriate extrusion temperature (Te) was evaluated to be about 673 K. The temperature-time-transformation (T.T.T.) diagram in the supercooled liquid region was also determined through the measurement of the time up to crystallization at various temperatures. The bulk glassy alloy prepared by extrusion at an extrusion ratio of 5 and Te=673 K has a nearly full density above 99% and the Tg, Tx and ΔHx values are the same as those for the as-atomized glassy powder with a particle size below 150 µm. Furthermore, the extruded bulk alloy also exhibits a tensile strength of 1520 MPa, a Young's modulus of 80 GPa and a tensile fracture strain of 0.02 which are nearly the same as those for the as-cast bulk and melt-spun glassy alloys. The fracture takes place along the maximum shear plane and the fracture surface consists of a well-developed ruggedness similar to the vein pattern typical for amorphous alloys with good bending ductility. The success of producing the bulk glassy alloy with high tensile strength by the extrusion method seems to be encouraging the future development of the Zr-based glassy alloy.
(Received June 7, 1995)
Keywords: bulk metal glass, zirconium base alloy, extrusion, atomized glassy powder, gas atomization, supercooled liquid region, full density, high tensile strength, shear-type fracture
† Graduate Student, Tohoku University.