Effect of Affected-Area Depth Induced by Surface Brushing on Bendability of Heavily Cold–Rolled Copper Alloy Sheet

Abstract

Improvement of bending workability of a heavily cold–rolled Cu–Ni–Si alloy sheet by surface wire brushing was investigated. Coarse pancake–like microstructure and sharp {110} texture developed in the heavily cold–rolled sheet were changed to equiaxed fine ones and rather randomized by the brushing at the vicinity of surface. Still more, work hardening induced by brushing penetrated into the deep areas of 500 μm from the surface. Such work hardening occurred more significant and severe with increasing applied pressure stress of brushing. By the modification of surface microstructure, bendability was largely improved without spoiling other mechanical properties, i.e., strength and ductility. R/t value of 1.2 by good–way bending, where R and t are the bending radius and thickness of sheet, was almost constantly achieved after ageing, while those without brushing were over 3 at best. It is revealed that the sufficient depth of work–hardened and influenced areas by brushing is 250 μm for the improvement of bendability. Furthermore, the orientation–randomized and fine–grained areas developed at the surface is more important than the wok–hardened area to achieve superior bendability.