Nobuyoshi Yano

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

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,Hv, and tensile strength,σf, are of the order of 425 to 440 DPN and 1670 to 1810 MPa. The elongation to fracture,εf, is about 2.4 to 2.7%. Cold drawing to about 30% reduction in area results in increases inσf andεf by about 10% and 35%, respectively. Furthermore, the addition of 5 at % niobium results in decreases inσf andHv 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.

Production of Ni-Pd-Si and Ni-Pd-P amorphous wires and their mechanical and corrosion properties

Wire-shaped nickel-based amorphous alloys exhibiting high strength and good ductility combined with a high corrosion resistance were produced for Ni-Pd-Si and Ni-Pd-P alloys by melt spinning in rotating water. The amorphous wires were formed over a relatively wide range from 29 to 82 at % palladium for (Ni-Pd)82Si18 alloys and from 12 to 52 at % palladium for (Ni-Pd)80P20 alloys. The Ni-Pd-Metalloid amorphous wires had a circular cross-section and smooth surface, and their diameters were 80 to 150μm. With increasing nickel content, their tensile strength, σf, increased from 1340 to 1710 MPa and the elongation to fracture, εf, decreased slightly from 2.2% to 1.9%. Cold-drawing the wires was an easy technique to reduce their diameter and to increase σf and εf up to an appropriate value of reduction in diameter. In addition, it is also effective in smoothing the wire surface. Their corrosion resistance was assumed to be sufficiently high since their polarization behaviour in 1 N H2SO4 solution was similar to palladium metal. Cold-drawing did not enhance corrosion and rather decreased apparently the active dissolution current density of some alloys owing to smoothing of the surface.

Uniaxial magnetic FeC thin films sputtered onto polymer substrates

Thin films of FeC were deposited onto a polymer substrate by reactive DC magnetron sputtering, using an argon and hydrocarbon gas mixture. The polymer web is wound by a roll coater, and an individual thin film with a constant thickness is piled up by increasing a number of passes UP to a desired thickness. Uniaxial films with Hk=4000 A/m and low dispersion were obtained. The coercive force was a function of thickness; it was Hc=8 A/m for films 0.8 /spl mu/m thick. The easy axis of the uniaxial anisotropy was along the direction transverse to the rolling direction of the polymer web. The origin of the uniaxial anisotropy is the anisotropic thermal shrinkage of the polymer web is discussed by a model.

Large Barkhausen discontinuity of Co-Fe-Si-B amorphous films sputtered on polymer substrate

Co-Fe-Si-B films have been prepared using a roll coater and DC magnetron sputtering system onto a polyethylene terephthalate substrate. This thin film exhibited an excellent uniaxial anisotropy introduced by an asymmetric thermal shrinkage of the substrate. Reversal with a single large Barkhausen pulse has been observed in thin film structure 1 mm by 50 mm by 0.65 /spl mu/m. Closure domains have been clearly identified at the film ends. The threshold for the reversal is the coercive force. The reason for reversal with a single Barkhausen jump is that the long narrow film geometry has essentially zero demagnetizing field over most of the film. Once the walls start to move through the center portion of the film, there is nothing to stop them so the reversal proceeds with a single large Barkhausen pulse.