【作者】 颜芳；

【导师】 孟亮；

【作者基本信息】 浙江大学 ， 材料加工工程， 2003， 硕士

【摘要】 通过大变形冷拉拔结合中间热处理制备了纤维相增强的Cu-12％Ag合金，研究了合金在不同加工状态下的显微组织及纤维相的形成过程。Cu-12％Ag合金铸态组织包括富Cu相基体和共晶体，共晶体中包含更细的两相层叠结构。在冷变形过程中，合金中各组织均演变成纤维状，尤其共晶体可演变为由更细密排列纤维组成的纤维束形态，并且Cu基体纤维中还包含大量在退火过程中析出的次生Ag相形成的细小Ag纤维。随着变形程度的提高，合金硬度和强度升高而相对电导率下降。所研制的合金可以在抗拉强度达1.02GPa时相对电导率仍能保持在78％IACS。 通过添加不同含量的稀土元素研究了稀土对Cu-12％Ag合金组织和性能的影响。结果表明，稀土元素能够改变合金铸态树枝晶形态和两相中Ag的饱和浓度，合金的晶粒尺寸随稀土含量增加而略有减小。微量稀土可以提高Cu-Ag合金的导电率，但当合金中稀土含量大于0.1％时，合金的导电率随稀土含量增加而降低。合金的硬度随稀土含量增加而得到改善，但强度没有明显改善。 采用不同温度退火的方法研究了试验合金导电性和抗拉强度随基体及强化相显微组织变化的关系。变形合金的双相纤维复合组织在200℃热处理时无明显变化，强度略有降低，硬度和导电性能略有升高。当热处理温度升高到400℃以上时，纤维组织演变成沿变形方向排列的等轴晶粒，合金强度及硬度显著下降，导电性能显著上升。适当的热处理工艺如果能使再结晶晶粒仅局限于纤维相内部生长而组织仍能保持完整的纤维形态，则合金能够表现出较好的强度与导电性匹配。 初步研究了热处理工温度对含稀土元素的Cu-12％Ag合金组织和性能的影响。结果表明，退火温度较低时稀土元素对Cu-12％Ag合金的组织和性能没有明显影响。当退火温度较高时，稀土元素使合金再结晶晶粒细小并促进了Ag的析出，在一定程度上使合金强度升高但使合金相对电导率降低。更多还原

【Abstract】 Cu-12%Ag filamentary composites were prepared by cold drawing combined and intermediate heat treatments. The ultimate tensile strength of 1 .02GPa with the electrical conductivity of 78%IACS in the wires was achieved with optimized preparation processes. The microstructure of the alloy at different working stage and the evolvement of the filaments were investigated. The as-cast alloy contains with both structures Cu-rich matrix and Cu-Ag eutectic. The eutectic consists of two-phase mixture of lamellar structure. During the cold drawing, both phases in the eutectic are elongated into fine filaments and the eutectic changes into the filament bundles. There are also a lot of thin Ag precipitates in the form of filaments distributing in the Cu matrix. With increasing draw ratio, the ultimate tensile strength increases while the electrical conductivity decreases for the alloy.The influence of rare earth elements on the microstructure and properties of the Cu-12%Ag was investigated. The morphology of the Cu dendrites and the Ag solubility in Cu phase were changed by adding rare earth elements. The grain size slightly decreased with increasing the content of rare earth elements. Suitable microalloying of rare earth elements in the alloy Cu-12%Ag can improve the conductivity. However, the conductivity decreases with increasing rare earth addition when the content of rare earth is higher than 0.1%. The hardness of the alloy enhances and the strength hardly changes with the addition of rare earth elemrnts.The influence of heat treatment after heavy cold drawing on the microstructure, mechanical and electrical properties of the alloy was investigated. For the alloy annealed at 200℃, the morphology of double-phase fibers formed during cold drawing shows an insignificant change but ultimate tensile strength slightly decreases, while hardness and conductivity slightly increase. For the alloy annealed above 400 ℃, the strength and hardness decrease and conductivity increases significantly. Moreover, the equiaxed grains aligned along the wire axis can be observed in the microstructure instead of filamentary morphology. It is possible to obtain the expected combination of better strength and conductivity for the alloy when the propagation of recrystallized grains is limited insidethe fibrous phases and the morphology of complete filamentary still kept down during annealing at suitable temperature.The influence of heat treatment on the microstructure, mechanical and electrical properties of the Cu-12%Ag alloys contained with rare earth elements was also investigated. After annealing at low temperature, the addition of rare earth elements has few effects on the evolution of microstructure and properties. After annealing at high temperature, the addition of rare earth elements refines the rycrystallization grains and improves the precipitation of Ag. The alloy containing rare earth elements possesses higher strength but lower conductivity after annealing at higher temperature than that free of rare earth elements.更多还原