An investigation on micro-hardness, micro-structure and ductility of clad layer in copper clad aluminum wire under multi stage-NCWD

Abstract

The copper clad aluminum (CCA) wire was fabricated by roll forming of copper foil around the aluminum wire rode. Non-continuous wire drawing (NCWD) was employed to study the effect of wire drawing parameters on ductility, micro-hardness and microstructure of the copper clad layer. The NCWD process continued without intermediate annealing until cracks were observed on the copper clad layer. The cracks appeared after a 78% reduction in the cross-section. The micro-tensile test was performed on specimens with transverse curvature to determine elongation. A modified correction factor was introduced to correct the effect of curvature size on elongation. The introduced correction factor proportional to the sample characteristics was between 0.7 and 1.4. Moreover, variations in the hardness and microstructure of the copper clad layer were investigated in the base metal and at the welding zone. Before beginning the wire drawing process for the annealed CCA wire with a diameter of 10.1mm and a Cu clad thickness of 0.48mm, the hardness, ductility, UTS and grain size of the clad layer were 87HV, 43%, 103MPa and 80 μm, respectively. At the end of NCWD for 10° and the 20% reduction ratio of the die, the diameter of CCA wire reached 4.7mm with a 0.22mm thickness of Cu clad. The hardness, ductility, UTS and grain size of the clad layer were 157HV, 2.9%, 325MPa and 8 μm, respectively.