Papers by Keyword: Pipe Diffusion

Abstract: Effect of dislocation behavior on formation of whisker in pure Sn has been investigated. Slip system in β-Sn was determined; slip plane is , and Burgers vector b is . The magnitude of Burgers vector is larger than the smallest interatomic spacing in β-Sn. This means that there is broad space under the extra half plane of edge dislocation. It sould be noted that pipe diffusion along the edge dislocation is enhanced in β-Sn, resulting in easy supply of Sn atoms at the root of Sn whisker [1, 2]. Si-bearing particles, which precipitate on surface of bulk Sn by heat-treatment in quartz tube, suppress the accumulation of both edge and screw dislocations to same area. It is greatly effective for the suppression of the nucleation of Sn whisker.

Abstract: A model for the nucleation and growth processes of Sn whisker is offered. High density of localized screw dislocations by deformation form the dense spiral steps of atomic scale on Sn surface. The spiral steps would induce the nucleation of Sn whisker. Edge dislocations localized at the same region where the dense screw dislocations exist supply Sn atoms to Sn whisker through pipe diffusion. Both screw and edge dislocations would bend along almost one direction, namely, to relax the external shear stress. The image force also helps to bend the dislocations perpendicular to the whisker side-surface. The bending of dislocations at root of whisker leads the bend of whisker. The pipe diffusion of Sn atoms through edge dislocations from bulk Sn toward whisker is suppressed at the bent part of edge dislocation, resulting in release of Sn atoms inside whisker and leading to the growth of whisker near its root.

Abstract: Activation energies for solute diffusion along dislocations are difficult to measure experimentally. The aim of this work is to provide insight into pipe diffusion with the help of atomistic simulations. The distribution of vacancy formation energy and the activation energy for copper migration are determined in the core of an edge dislocation in aluminum. The Dimer method is used to find activation energies for vacancy migration. The activated region around the dislocation where a very high diffusivity is observed and the activation energy for copper diffusion associated with this region are interpreted with regard to the contribution of the dislocation and the contribution of the alloying.