On the strain inhomogeneity in drawn copper wires

Three different wire drawing schedules were attempted to examine the effects of reduction of area, die-angle and friction coefficient on the strain inhomogeneity of drawn copper wires. The microhardness distribution was studied over the transverse and longitudinal cross-sections. Inhomogeneity factor (I.F.) curves; I.F. = f(r), I.F. = g(2α) and I.F. = h(μ) were determined from the measurements. The results indicate that less strain inhomogeneity is achieved in drawing wires through dies with low angle, low friction coefficient and high reduction of area. Despite the variation in reduction of area and die-angle, the strain was distributed evenly at the center of the drawn wires. Contrary to the existing theoretical models, inhomogeneity factor versus deformation zone geometry parameter (∆) was approximated by a second order polynomial curve and not a linear relationship, as was previously postulated. A new relationship was also proposed to relate the I.F. to the calculated redundant work factor Φ.