PROPERTY OF ULTRAFINE GRAINED ENGINEERING MATERIALS RELATED TO HIGH MAGNETIC FIELDS

摘要

Deformation is used to fabricate various materials for high field magnets. The key materials possess ultrafine microstructure and unique combination of mechanical and physical properties. The matrix of the materials discussed in this paper has face-centered cubic (fcc) structure and therefore no ductile-to-brittle transition temperature is observed. The properties of these magnet materials are related to the microstructure. A number of Cu matrix conductors have strength levels close to their theoretical strength because the size of the grains reaches nanometer scales. However, the electrical resistance is also increased because of the refined microstructure. The application of these materials requires detailed consideration of the mechanisms of strengthening and electron transport which are operative in materials with ultra fine scale microstructures. In addition, consideration must be given to the fatigue endurance of those composites. The second type fcc matrix materials are low temperature superconductor composites. The critical current of Nb3Sn superconductors is related to the mechanical strain to which the materials are exposed. To achieve high strength, refinement of microstructure is also required. However, ultrafine structure may result in deterioration of transport properties. The third type fcc matrix materials are super alloys. This paper mainly summarizes our studies of the cryogenic properties of a Co-Ni-Cr alloy. The refined structure in this alloy provides a strength level as high as 2500 MPa. This presentation will address the correlation between the properties (both mechanical and transport) and microstructure of those fcc matrix magnet materials.