Recristalização das ligas supercondutoras do sistema Nb-Ti

AUTOR(ES)
DATA DE PUBLICAÇÃO

1986

RESUMO

Multifilamentary cables of Nb-Ti alloys have been used mainly in superconducting engines and devices. These alloys have high ductility and their final most important superconducting properties can be established by suitable metallurgical procedures. In this work the influence of the microstructural characteristics on the superconducting properties and of the mechanothermal processing on the microstructural transformations are discussed. All the steps for the preparation of 50 mm x 200mm Nb-Ti ingots by electron beam melting are described in detail. A procedure to follow the microstructural transformations in the Nb-Ti alloys with titanium content in the 44-53 wt% range is also presented. The ingots after fusion were cold worked by swaging. The deformation grades have been designed according to the final rod diameter; there is a required rod diameter for the fabrication, of the superconducting composite multifilamentary cables. A broad microstructural characterization of the starting rods is necessary because it is the base for thefinal properties of the superconducting cables. Hence attention has been paid to the composition and microhardness variation along the ingot and the rods, the development of deformation cells, the recrystallized fraction, the average grain size, the precipitation and texture as a function of deformation grades, annealing temperature and time. Chemical as well as microstructure analyses have been carried out by means of the follow.ing techniques: atomic absorption gas (N2 and 02) chromatography, X-ray diffractometry, qualitative and quantitative optical metallography, transmission electron microscopy, and microhardness. The main results show that from the technological approach, the procedures for the preparation of Nb-Ti rods with well defined composition, diameter and granulometry are established; from the basic mechanisms approach, an understanding of several phenomena ocuring during processing, namely, work hardening, homogenization, recovery, recrystallization, grain growth and secondary recrystallization is attained

ASSUNTO(S)

recristalização (metalurgia) supercondutores

ACESSO AO ARTIGO

Documentos Relacionados