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 (R_A). In addition, the fraction of high angle grain boundaries tended to increase with the increase of R_A. 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 R_A. Recrystallization texture of (001)[100] and (110)[001] began to appear at an R_A higher than 84%. The hardness tended to increase with increasing R_A due to work hardening. In particular, increasing R_A 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 R_A above 84%, even when R_A was increased to 96%. The strength also tended to increase stepwise as R_A increased, very similar to the change in hardness. The specimen with an R_A 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 R_A, and remained at an average value of 61.6 %IACS.