Voids in quenched copper, silver and gold

Abstract

In copper, silver and gold, quenched into silicone oil, large voids are formed by vacancy clustering in addition to faulted loops and stacking-fault tetrahedra. The shapes of voids were studied in detail in copper and it was found that the shape depended on the quenching atmosphere. For copper quenched from carbon monoxide, the surfaces of the voids were {111} planes or {111} and {001} planes, but {101} surfaces were not found. The incidence of regular octahedral voids with {111} surfaces was low, but most of the voids could be described as regular oetahedra truncated by {111} or {111} and {001} planes. Some voids with {111} surfaces had more complex shapes and could be described as truncations of a polyhedron made up of a regular octahedron with a tetrahedron on one face. The shapes of voids in copper quenched from hydrogen were similar to those in copper quenched from carbon monoxide. In copper quenched from vacuum or argon, the voids were rounded and were shown to have {101} surfaces in addition to {111} and {001}. The results suggest that the presence of oxygen can modify the shape of a void formed by vacancy clustering. On annealing, voids with only {111} surfaces develop {001} and {101} surfaces and thus appear rounded. It is shown that increasing the amount of hydrogen in solution in copper and of hydrogen or oxygen in solution in silver, favours void formation. The results on the influence of gas in solution on void formation in gold were not conclusive. Hydrogen in solution in copper is shown to cause prismatic punching of dislocations from voids during quenching, whereas oxygen in solution causes prismatic punching from oxide particles.