| Because of their unique combination of strength and conductivity, in-situ deformed copper composites have potential applications as the high pulsed magnetic field conductors, lead frames and other devices. Especially, in-situ deformed Cu-Fe composites have been widely attracted since their strengths are significantly increased by the addition of Fe and the cost of Fe is lower. Optimizing the relationship between the strength and conductivity and raising the combination property are concerned in the investigations on Cu-Fe composites. This research is supported by the National High Technology Research and Development Program of China (863Project)(No.2007AA03Z519). In this thesis, in-situ deformed Cu-15%Fe composites are manufactured by vacuum induction melting, hot swaging and wire drawing. The effects of drawing ratio and annealing process on microstructure and mechanical/conductivity properties of Cu-Fe composites are investigated. The followings are the results.1. The research on microstructure evolution of Cu-15%Fe composites indicates that with the increasing of the drawing ratio, the Fe dendrites homogeneously distributed are aligned parallel to the drawing direction and formed the elongated ribbons-like curved filaments in the cross sections. It is caused by the<110>-fiber texture in the bcc crystallography of Fe formed by plane strain during the drawing process. Based on the quantitative metallographic analysis, the relationship between the filament spacing and the drawing ratio, d=41.76exp (-0.411η), is satisfied. And the formula between the filament thickness and width and the drawing ratio can be expressed as ln(tFe)=3.396-0.686η、ln(wFe)=4.114-0.431η, respectively.2. The investigations on the mechanical/conductivity property of the Cu-15%Fe composites show that the strengths of Cu-Fe composites are increased with the increasing of the drawing ratio. The ultimate tensile strength of Cu-Fe composites isn’t predicted by the ROM model at higher drawing ratio (η>5.0). When the drawing ratio η is8.9, the strength of Cu-Fe composites is up to1020MPa. And the yield strength and the filament spacing are satisfied the Hall-Petch equation, σy=350.09+13.89d-1/2. With the increasing of the drawing ratio the conductivity is ranged from49.54%IACS to56.89%IACS, which is determined by the intrinsical property.3. The Investigations on annealed microstructure of Cu-15%Fe composites reveals that if the holding time is fixed at1h, the morphology of Fe filament is not obviously changed when the annealing temperature is lower than400℃. However, when the annealing temperature is higher than600℃, some of the Fe filaments occur cylinderization, splitting and even spheroidization, which destroys the morphology and continuity of Fe fibers. If the annealing temperature is fixed at450℃,as the holding time is exceeded4h, the Fe filaments occur cylinderization and splitting. The Fe filaments were not further broken when the time is in excess of12h.4. The investigations on mechanical/conductivity properties of the annealed Cu-14.5%Fe composites show that the tensile strength and microhardness are gradually reduced with the annealing temperature, while the conductivity firstly increases and then decreases due to the influence of matrix and fiber morphology. With the increase of the holding time, the tensile strength and microhardness sharply is lowered firstly, then gradually stabilized. However, the conductivity is just the opposite. The investigation of different cooling conditions such as furnace cooling, air cooling and water quench reveals that their effects on properties of composites are not obvious, and air cooling can meet the need.5. The optimum annealing conditions of Cu-15%Fe composites are the annealing temperature of450～500℃, the holding time of1-2hours, and air cooling. The tensile strength of annealed Cu-Fe composites is up to555-615MPa, and the conductivity is up to58.8-59.9%IACS. |
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