The effects of microstructure on the bend formability of an age-hardenable Cu-4 mass%Ni-1 mass%Si-0.02 mass%P alloy have been investigated. A number of micro necks first arise along grain boundaries, and part of them grows, resulting in surface wrinkles, which finally lead to surface cracking. The wrinkles occur by shearing in the vicinity of grain boundaries. The width of precipitate-free zones has been found to be one of the factors affecting the bend formability. The grain-boundary shearing takes place more easily, resulting in worse bend formability as the width of precipitate-free zones increases. The bend formability is improved by two-step aging.
