Cold drawing of micro Ni80Fe20/Cu composite wires

The development of sensing elements for magnetic field sensors requires the use of soft magnetic materials. The method of cold drawing is well suited for the production of such microwires due to its ability to produce uniformity in wires with good composition control. The objective of this study is to develop and optimize the cold drawing technique of composite microwires. In this study, composite microwires of external diameter 42 μm, with thickness ratios of 1:4:1 and 1:10:1, were developed. The effect of the final annealing temperature on the surface morphology of the composite wires was also investigated. This paper presents in detail the cold drawing technique of composite microwires. The results showed that there was a protruding effect of the Cu after the first draw and this protrusion decreased after subsequent draws in the earlier draws. Since the ratio of the diameter of the Cu core to the overall diameter remained relatively unchanged throughout the process, the rule of the conservation of volume can be used to predict the final diameter and length of the composite wire. When the annealing temperature was increased to beyond 850 °C, significant changes to the surface morphology occurred.