Production of metal-zirconium type amorphous wires and their mechanical strength and structural relaxation

Abstract

Metal-metal type amorphous wires with a good ductility were produced in the M-Zr (M=Cu, Cu-Nb and Cu-Ta) alloy systems by a technique using melt spinning into rotating water. The formation of the amorphous wires is limited to a narrow range of 35 to 40 at % zirconium where the critical sample thickness for the formation of an amorphous phase is above about 100μm and the amount of copper replaced by niobium or tantalum is less than about 7 and 5 at %, respectively. The wires have a circular crosssection and a rather smooth peripheral surface. Their diameters are in the range of 0.07 to 0.15 mm. The Vickers hardness,H_v, and tensile strength,σ_f, are of the order of 425 to 440 DPN and 1670 to 1810 MPa. The elongation to fracture,ε_f, is about 2.4 to 2.7%. Cold drawing to about 30% reduction in area results in increases inσ_f andε_f by about 10% and 35%, respectively. Furthermore, the addition of 5 at % niobium results in decreases inσ_f andH_v by about 14% and 4%, respectively, without detriment to the good bending ductility. Owing to the faster quench rates of the wire samples, caused by the inherent differences in the solidification process of the ejected melt as well as in the manner of cooling after solidification, the amorphous wires have been found to exhibit a considerably higher relaxation enthalpy value, ΔH, and a lower temperature for the onset of structural relaxation as compared with the amorphous ribbon having the same thickness as the diameter of the wire, demonstrating that the amorphous wires possess a higher degree of structural disorder.