Mechanical properties of Zr 57Ti 5Al 10Cu 20Ni 8 amorphous and partially nanocrystallized alloys

Abstract

Zr 57Cu 20Al 10Ni 8Ti 5 amorphous cylinders of 8 mm diameters were cast with copper moulds. The mechanical properties of the amorphous alloys obtained were measured by compression tests. The as-cast amorphous alloys show a high yield stress of about 1560 MPa and fracture stress of 1650 MPa. Structural relaxation, through annealing below the glass transition temperature, for example, at 573 K for 40 min, increases these values to about 1700 and 1760 MPa, respectively. Annealing of the amorphous alloy in the supercooled liquid region causes initial crystallization, but the residual amorphous phase becomes relatively stable. The partially crystallized amorphous alloy, for example with about 40% (vol) crystalline phase, still shows excellent strength, with a yield stress of 1700 MPa and a fracture stress of 1850 MPa. Both the as-cast and annealed amorphous alloys show ductile deformation with serrated flow before final fracture. These results indicate that amorphous alloys with such crystallization behaviour can be quite safely hot-worked near the glass transition temperatures.