Ming Liang

Characteristics of High Strength and High Conductivity Cu-Nb Micro-Composites

We have fabricated Cu-Nb composites with high strength and high conductivity by bundling and drawing process for their application in high field pulsed magnets. Several kinds of composites are designed for investigation of the filament-size and interface effect on the strength and conductivity. For Cu-Nb micro-composites with a section of 5 mm2 composed of a Cu matrix embedded 5 × 107 continuous Nb nano-fibers with a diameter of 100 nm, our results have shown that the ultimate tensile strength reaches 1 GPa while the electrical conductivity is higher than 70% IACS at room temperature. Since the size of Nb filaments is already on a nanometer scale, the size effect on microstructure and property of Cu-Nb composites has been studied.

Thermal Stability of Cu-Nb Micro-Composites by Bundling and Drawing Process

We have fabricated high strength and conductivity Cu-Nb micro-composites by bundling and drawing process. We study the thermal stability of Cu-18vol. %Nb composites for high pulsed magnet use. The evolution of the Nb filaments in the composites during heat treatments is observed by scanning electron microscopy. The mechanism of edge spheroidization and cylinderization phenomenon for Nb filaments is discussed. The changes in mechanical and electrical properties of the Cu-Nb composites resulting from heat treatments are measured. The treatment effect on the properties of the composites with a different size of the Nb filaments is discussed.

Annealing Effects on the Microstructure and Mechanical Properties of Cu-Nb Microcomposites

The annealing effects on the microstructure of Cu-Nb microcomposites fabricated by bundling and drawing process have been studied. During annealing at temperature as high as 800, the intensity of (110) diffraction peak of Nb became sharper and higher. The significant cylinderization and coarsening phenomenons of the niobium filaments were observed. The influence of microstructural changes on the hardness and the tensile strengths of Cu-Nb wires were discussed.

Heat Treatment Effect on the Magnetic Properties of Cu-Nb Micro-Composites

We develop Cu-Nb micro-composites with high strength and conductivity by bundling and drawing process for high pulsed field magnets. We report the heat treatment effect on the magnetic, mechanical properties of Cu-17 vol.% Nb composites. Within the heat treat temperature of 450°C ~ 800°C, noticeable changes take place in the magnetic properties of composites, since recovery and recrystallization of the Nb fibers and the Cu matrix happen under different treatment conditions. The characteristic of magnetic hysteresis curves caused by the proximity effect and controlled by the Cu/Nb interface structure of the Cu-Nb micro-composites is discussed.