Mechanical Properties and Thermal Stability of Ti- and Al-Based Amorphous Wires Prepared by a Melt Extraction Method

Abstract

The application of a melt extraction method to Ti- and Al-based alloys with highly reactive molten states was found to cause the formation of continuous amorphous alloy wires with good bending ductility. The wire diameter is in the range of 40 to 150 μm for Ti 40 Zr 10 Cu 50 and 40 to 100 μm for Al 85 Ni 10 Ce 5 and the difference reflects the difference in the glass-forming ability between both alloys. The glass transition temperature, crystallization temperature and heat of crystallization are 629 K, 691 K and 1.71 kJ/mol, respectively, for the Ti-based wire with the diameter of 100 μm and 530 K, 546 K and 0.37 kJ/mol for the Al-based wire with the diameter of 50 μm. The tensile strength is 2000 MPa for the former wire and 930 MPa for the latter wire. The thermal stability and mechanical strength are nearly the same as those for the melt-spun amorphous ribbons with the thickness of 15 μm. No appreciable concave resulting from the use of the copper wheel with a steep edge is seen in the cross section and the solidification is completed during the flight after extraction. The cooling rate of the Al-based wire with the diameter of 70 μm is estimated to be of the order 6 x 10 4 K/s. Thus, the formation of the amorphous alloy wires with a circular cross section is due to the rapid solidification of the fine supercooled liquid stream in the suppression of heterogeneous nucleation during the high-velocity flight in the argon atmosphere. The combination of the solidification process with high cooling rate and the good formability into the wire shape allows us to expect that the present process develops as an alternative method to produce amorphous alloy wires in various kinds of alloy systems including reactive elements as main components.