晶粒形态、尺寸对Ag-28Cu-0.75Ni合金超细丝加工及电学性能的影响

Effects of Grain Morphology and Size on Processing and Electrical Properties of Ag-28Cu-0.75Ni Alloy Ultra-fine Wire

摘要:

为诠释柱状晶贵金属兼具优良超细丝加工性能及高电阻率的原因,采用水平连铸、水冷铜模铸造及石墨模铸造,分别获得了具有20 μm×60 μm的柱状晶、10 μm的等轴晶、以及5 μm的表面细晶+长径比约为3的柱状晶+30 μm的芯部等轴晶三晶区的三种Ag-28Cu-0.75Ni合金棒材,研究了晶粒形态、尺寸对Ag-28Cu-0.75Ni合金棒材超细丝加工性能及电阻率的影响。结果表明：与等轴晶和三晶区Ag-28Cu-0.75Ni合金棒材相比,柱状晶棒材由于其较低的位错密度(1.78×10_¹⁵ m_^-2)及显微硬度变化率(33.3%)、铸态断口无解理台阶,表现了出最低的加工硬化率,且铸态轴向抗拉强度高达384.6 MPa,可实现100 m以上、直径0.05 mm超细丝高效不断丝加工；加工态及退火态的柱状晶Ag-28Cu-0.75Ni合金超细丝均表现出了较高的电阻率,经两次连续退火后电阻率高达3.68 μΩ.cm,与其较低的位错密度及加工硬化率有关。

Abstract:

In order to explain the reason why the columnar crystal precious metal has excellent ultra-fine wire processing property and high resistance, three kinds of Ag-28Cu-0.75Ni alloy bars, columnar crystal of 20 μm×60 μm, equiaxed crystal of 10 μm, and tri-crystal zone with surface fine crystal of 5 μm + columnar crystal with length diameter ratio of around 3 + core equiaxed crystal of 30 μm, were obtained by horizontal continuous casting, water-cooled copper die casting, and graphite die casting, respectively. The effects of grain morphology and size on the ultra-fine wire processability and resistivity of Ag-28Cu-0.75Ni alloy bars were studied. The results show that, compared with the equiaxed crystal bar and the tri-crystal zone bar, the columnar crystal bar has the lower dislocation density (1.78×10_¹⁵ m_^-2), the lowest ratio of micro-hardness change (33.3%), and no cleavage step after the tensile test, thus, it presents the lowest work hardening rate. Besides, the axial tensile strength of as-cast columnar crystal bar is up to 384.6 MPa. Therefore, the ultra-fine wire with the diameter of 0.05 mm and the length of 100 meters or more can be obtained by the high-efficiency continuous wire drawing of the columnar crystal bar. The resistivity of processed and annealed Ag-28Cu-0.75Ni alloy ultra-fine wires that drawn from the columnar crystal bar are higher, after two times continuous annealing, the resistivity of columnar crystal Ag-28Cu-0.75Ni alloy ultra-fine wire is up to 3.68 μΩ.cm, which is related to the lower dislocation density and work hardening rate.