中文摘要：

采用连续铸造技术制备Ag-28Cu-0.75Ni（%,原子分数）合金棒材,真空退火后进行冷拉拔加工,分别采用X射线衍射（XRD）、金相显微镜（OM）和扫描电镜（SEM）对合金的物相、铸态、加工态和断口组织进行表征,并对导电率、硬度、强度和延伸率进行测试。结果表明：Ag-28Cu-0.75Ni的显微组织为：以Ag,Ni为溶质的Cu相固溶体,以Cu为溶质的Ag相固溶体和共晶（Ag＋Cu）结构;其连铸态微观结构为典型的表面细晶区、柱状晶区和中心等轴层片状晶区三区结构,铸锭中散落着形貌清晰、形态规整的枝晶,枝晶偏析以及中心等轴区的边界偏析造成易腐蚀的低熔点区域。同时,材料本身加工态横截面晶粒细化、组织均匀,纵截面晶粒由点块状变为纤维状,发生择优取向形成形变织构。随真应变的增加,强度、硬度随之增加,而导电率、延伸率下降。

英文摘要：

The Ag-28Cu-0.75Ni（ % , atom fraction） alloy bars were processed by cold drawing after vacuum annealing which were produced by continuous casting technology. The phases, cast states, working states and fracture morphologies were characterized by X- ray diffraction （XRD） , metalloscope and scanning electron microscopy （ SEM ） , respectively. At the same time, the electrical conduc- tivity, hardness, strength and elongation were tested. The results showed that Ag and Ni were solid dissolved in Cu phase solid solu- tion, Cu was solid dissolved in Ag phase solid solution and eutectic structure （ Ag ＋ Cu） was also found. The microstructures of casting state alloy included surface fine grain area, columnar grain zone and center equiaxed lamellar crystal region that were typical three - zone structures. The dendrites which were of clear and regular shape morphology were scattered in the ingot. However, the corrosion of low melting point was easily led by dendrite segregation and boundary segregation of center equiaxial c17stal zone. Grain refinement process appeared in the cross section and its organization became homogeneous; for the longitudinal section grain, the shape changed from point to fibrous lumps, generated preferred orientation and formed deformation texture. The strength and hardness of the alloy in- creased with the true strain increasing, while the conductivity and elongation reduced.