Microstructural study on the processing and properties of high-field A15 superconducting materials
Abstract
Superconducting properties of high-field A15 materials were studied in terms of the physical and chemical states of the A15 phases. Higher critical current is achieved through microstructural control. The A15 materials investigated include the V3Ga and Nb3A1 phases formed by a direct-precipitation process, the multifilamentary Nb3Sn formed by the bronze-process, and the bronze-processed Nb3Sn with a Mg addition. The direct-precipitation process was found to have an intrinsically inferior critical current and lower stability, due to the large effective grain size, of stoichiometric composition, and the high stability of bcc films between A15 grains. For the bronze-processed Nb2Sn multifilamentary wire, microscopic examination reveals that the reacted layer consists of a three-shell composite structure. A mechanism to account for the formation of this structure is proposed. The critical current density is apparently determined by the areal fraction, grain size and composition of the central, fine-grained layer.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- August 1984
- Bibcode:
- 1984PhDT........16W
- Keywords:
-
- Bronzes;
- Heat Treatment;
- Microstructure;
- Precipitation (Chemistry);
- Superconductivity;
- Aging (Metallurgy);
- Current Density;
- Gallium Alloys;
- Grain Size;
- Niobium Alloys;
- Tin Alloys;
- Vanadium Alloys;
- Solid-State Physics