Frederick A. Schmidt

Processing to optimize the strength of heavily drawn Cu-Nb alloys

Heavily drawn Cu-Nb alloys display quite high ultimate tensile strengths. A modification to the consumable arc-casting technique used to prepare these alloys is shown to decrease the as-cast niobium dendrite diameter,t0, and also increase strength. Evaluation of strength, niobium filament spacing and thickness data show that strength varies with as-cast niobium dendrite size as somewhere betweento−0.36 toto−0.50. Splat-cooling techniques demonstrate that minimum niobium dendrite sizes as small as 0.22μm are possible. These sizes are over a factor of 10 smaller than has been achieved by consumable arc casting, and it is therefore suggested that processing rapidly solidified powders of Cu-Nb alloys should have significant advantages for preparing high-strength heavily drawn Cu-Nb alloys.

Casting of dendritic Cu‐Nb alloys for superconducting wire

Consumable electrode‐arc‐casting techniques have been developed for the preparation of large billets of dendritic Cu‐Nb alloys which are suitable for the fabrication of multifilamentary superconducting wire. The dendrite structure is somewhat more coarse than chill cast material but metallographic and chemical analyses show acceptably small radial and longitudinal segregation. The billets can be drawn to wire with no intermediate anneals. Both external diffusion after tin plating and internal diffusion of wire with a tin core can be used to transform the Nb filaments to Nb3Sn. The arc cast wire displays Jc values equivalent to previously reported values on in situ wire at high fields, but somewhat lower values at low fields.

Preparation of Cu-Nb alloys for multifilamentaryin situ superconducting wire

A study has been made of two techniques, chill casting and consumable arc melting, for preparing ingots of Cu-Nb alloy for production of multifilamentary Nb3Sn superconducting wire. It was found that Y2O3, ThO2 and graphite all make excellent crucible materials for melting Cu-Nb alloys at 1850° C. Some difficulty was found with Nb segregation in chill-cast 5 cm diameter ingots. The consumable arc casting technique was shown to produce a uniform Nb dendrite distribution with little macrosegregation in 5 cm diameter castings and is regarded as having excellent potential for scale-up production of uniform Cu-Nb ingots of 25 to 30 cm diameter.

DEFORMATION PROCESSED Cu-REFRACTORY METAL COMPOSITES

ABSTRACT Recent studies have shown that heavily drawn Cu-Nb alloys can achieve strengths above 2000 MPa and outstanding combinations of strength plus conductivity (both electrical and thermal). The properties result from an aligned composite structure formed by a mechanical reduction which produces ribbon shaped Nb filaments In the Cu matrix. These metal-metal matrix composites are referred to here as deformation processed composites (DPC). A whole series of metal-metal matrix Cu-X alloys may be prepared by deformation processing, where X may be any of the BCC metals: V, Nb, Ta, Cr, Mo, W or Fe. Processing consists of two primary steps: preparation of the Cu-X billet with the X phase uniformly dispersed as small particles, and then a very large mechanical reduction. The billet may be prepared by either solidification or powder processing. Existing experimental results are reviewed, some new data on powder processed Cu-W are presented, and the general applicability of solidification processed and powder pr...

Superconducting YBa2Cu3Ox particulate produced by total consumption burner processing

Abstract This paper summarizes the results on the characterization of fine particulates of YBa2Cu3Ox superconducting oxide produced by reacting an atomized nitrate solution containing yttrium:barium:copper in the atomic ratio 1:2:3 respectively, in an oxyhydrogen flame. The characterization of the resulting oxide compound includes microstructural analysis by optical microscopy and scanning electron microscopy (SEM), X-ray diffraction and magnetic susceptibility measurements. SEM reveals the primary particle size (about 0.1−0.3 μm) and morphology of a substrate deposit, produced from solution concentrations ranging from 5 to 33 g l−1. X-ray diffraction measurements of oxygen-annealed particulate reveal a crystal structure identical with that of the conventionally produced superconducting oxide. Magnetic susceptibility measurements using a superconducting quantum interference device magnetometer demonstrate that the material is superconducting with a Tc of about 93 K.

CRADA (AL-C-2009-02) Final Report: Phase I. Lanthanum-based Start Materials for Hydride Batteries

The purpose of Phase I of this work is to focus on developing a La-based start material for making nickel-metal (lanthanum)-hydride batteries based on our carbothermic-silicon process. The goal is to develop a protocol for the manufacture of (La{sub 1-x}R{sub x})(Ni{sub 1-y}M{sub y})(Si{sub z}), where R is a rare earth metal and M is a non-rare earth metal, to be utilized as the negative electrode in nickel-metal hydride (NiMH) rechargeable batteries.