抄録
Structural changes associated with outward diffusion of zinc in single and poly-crystals of a brass are studied by metallographic and X-ray techniques. The dezincification is carried out in a vacuum at high temperatures. The results observed in the diffusion zones are. summarized as follows:
Great numbers of dislocations are produced in the diffusion zones by plastic deformation and vacancy condensation. A large amount of slip is caused near the free surface of the specimen, which is clearly observable at low diffusion temperatures. Density of dislocation and fineness of the sub-structure are higher near the free surface than in the inner part. These structural changes result from generation and subsequent redistribution of dislocations by slip and rise during the diffusion.
Some of the aggregations of dislocation etch-pits in the diffusion zones indicate that some dis-locations are formed from the vacancy condensation. In the case of single-crystal specimens, specially orientated voids are seen developed in the diffusion zones at high temperatures and during long diffusion time, the voids developing along a particular lattice plane.
It is concluded that the dislocations produced by plastic deformation and vacancy condensation during the dezincification can behave to accelerate the outward diffusion of zinc. Furthermore, present results substantiate both theories of Brinkman2) and Balluffi2) that a tensile stress arises and a state of vacancy supersaturation exists in the diffusion zones suffering a net loss of atoms.
