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Melt-textured growth of polycrystalline YBa2Cu3O7−δ superconductor using directional solidification created an essentially 100% dense structure consisting of long, needle- or plate-shaped crystals preferentially aligned parallel to the a-b conduction plane. The new microstructure, which completely replaces the previous granular and random structure in the sintered precursor, exhibits dramatically improved transport Jc values at 77 K of ∼17 000 A/cm2 in zero field and ∼4000 A/cm2 at H=1 T (as compared to ∼500 and ∼1 A/cm2, respectively, for the as-sintered structure), with the severe field dependence of Jc (‘‘weak-link’’ problem) no longer evident in the new melt-textured material. The improvement in Jc is attributed to the combined effects of densification, alignment of crystals, and formation of cleaner grain boundaries. Microstructure and distribution of various phases present in the melt-textured material are discussed in relation to the superconducting properties.

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New high-strength Pb-free solder alloys, based on the Sn-Ag-Zn system, have been developed. A relatively small addition of Zn significantly improves the mechanical strength of Sn-3.5% Ag eutectic solders while maintaining the same level of ductility. The observed increase in strength is as much as 48% over that of the Zn-free alloy. This strengthening from the Zn additions is attributed to a substantial refinement of the precipitates in the solidification microstructure. The problems of nonuniformity in solidification dendrite structure and solder surface roughness often observed in the Sn-Ag binary alloys are also alleviated by the Zn addition. It is found that essentially all of the added Zn resides in the more corrosion-resistant, Ag-based, intermetallic precipitates, leaving the Sn-rich matrix primarily free of Zn in solid solution. High-temperature creep tests indicate that the new Zn-containing alloys exhibit a remarkably improved creep resistance of more than an order of magnitude.