Metallurgical Processing and Superconducting Parameters of the V3Ga A15 Phase.
Abstract
The solid-state bcc-to-A15 phase information in V3Ga, the extension of this A15 phase field on both sides of the stoichiometric composition, and the high-field current-carrying capacity of V3Ga composite wires make V3Ga attractive for investigating how structure determines superconducting properties. However the extended freezing range in the V-Ga binary system promotes both dendritic segregation and a large-scale radial Ga gradient. For systematic study of the interrelations among the metallurgical processing procedures, the resultant microstructures, and the superconducting properties of the V3Ga A15 phase, eleven alloys, spanning the composition range of the A15 phase field and the adjacent two-phase fields, were arc-melting and cast as 1.3 cm-diameter rods. The dendritic segregation in the cast materials was made visible in metallographic sections by etching. A brief heat treatment at temperatures in the bcc-phase field eliminates the dendritic segregation and reduces the radial Ga gradient. By rapidly cooling the specimen through the bcc-to-A15 transformation, segregation from the transformation is on a fine scale and can be removed by a subsequent anneal within the beta-phase field. The transformed microstructures and the annealed microstructures of all materials of the V3Ga A15 phase were similar, and even microhardness was nearly constant over the full broad composition range of the V3Ga phase. The lattice parameter of the A15 V3Ga phase, measured by powder x-ray diffraction, increased with increasing Ga content. The present measurements define two lines intersecting near the V3Ga composition.
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 10, 1975
- Accession Number
- ADA015944
Entities
People
- B. N. Das
- J. E. Cox
- R. W. Huber
Organizations
- United States Naval Research Laboratory