Changes in Microstructure, Mechanical and Electrical Properties with Progress of Cold Wire-Drawing for AA1070

Abstract

Commercial AA1070 alloy for electrical wire is severely deformed by the drawing process when a rod with a diameter of 2 mm is greatly reduced to 0.4 mm by multi-pass. Changes in the microstructure, mechanical properties, and electrical properties of the Al alloy during the wire-drawing process were investigated in detail. The as-drawn Al wires showed a deformation structure in which the grains are greatly elongated in the drawing direction, even though recovery and/or partial recrystallization occurred more actively in the specimens which had more than 84% in reduction of cross-sectional area (<i>R<sub>A</sub></i>). In addition, the fraction of high angle grain boundaries tended to increase with the increase of <i>R<sub>A</sub></i>. For all drawn specimens, the fiber texture of the {110}<111> and {112}<111> components was mainly developed, and their maximum intensity tended to increase with increasing <i>R<sub>A</sub></i>. Recrystallization texture of (001)[100] and (110)[001] began to appear at an <i>R<sub>A</sub></i> higher than 84%. The hardness tended to increase with increasing <i>R<sub>A</sub></i> due to work hardening. In particular, increasing <i>R<sub>A</sub></i> to 84% resulted in a great rise in hardness, accompanied by a distinct non-uniformity in hardness in the thickness direction. However, the average hardness hardly changed at <i>R<sub>A</sub></i> above 84%, even when <i>R<sub>A</sub></i> was increased to 96%. The strength also tended to increase stepwise as <i>R<sub>A</sub></i> increased, very similar to the change in hardness. The specimen with an <i>R<sub>A</sub></i> of 93% showed the highest tensile strength of 192 MPa, 2.8 times higher than that of the specimen before drawing. The electric conductivity did not decrease significantly, even with extreme increases in <i>R<sub>A</sub></i>, and remained at an average value of 61.6 %IACS.