Effects Of Grain Morphology And Size On Processing And Electrical Properties Of Ag-28cu-0.75ni Alloy Ultra-Fine Wire

In order to explain the reason why the columnar crystal precious metal has excellent ultra-fine wire processing property and high resistivity, three kinds of Ag-28Cu-0.75Ni alloy bars, columnar crystal of 20 mu mx60 mu m, equiaxed crystal of 10 mu m, and tri-crystal zone with surface fine crystal of 5 mu m + columnar crystal with length diameter ratio of around 3+core equiaxed crystal of 30 mu m, 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 (Ag phase is 1.78 x10(15) m(-2), Cu phase is 1.34x 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 drawing wire of the columnar crystal bar. The resistivity of processed and annealed Ag-28Cu-0.75Ni alloy ultra-fine wires drawn from the columnar crystal bar is higher; after twice continuous annealing, the resistivity of columnar crystal Ag-28Cu-0.75Ni alloy ultra-fine wire is up to 3.68 mu Omega.cm, which is related to the lower dislocation density and work hardening rate.