Structure and orientation relationship of precipitates formed in Al-Cu-Mg-Ag alloys

Abstract

Precipitates which form on {111} planes of the Al-Cu-Mg alloy lattice when small amounts of silver are added are newly established as having a hexagonal structure with a = 0.496 nm and c/a = 1.414. The [0001] direction in the precipitate is aligned parallel to a 〈111〉 direction in aluminium with 〈1010〉 parallel to 〈110〉, giving close registry of the respective crystal lattices. A small addition of zinc reduces the size of precipitate but does not change the crystal structure.