Papers by Keyword: Cavity Growth

Abstract: Cavity growth is a typical microstructure feature in superplastic forming (SPF) of materials. Substantial growth and interlink of cavities in superplastic deformation usually lead to reduction in elongation, even to failure. Consequently, it is necessary to investigate the mechanism and model of cavity growth. In this paper, experimental studies on cavity growth were carried out by means of superplastic tension of ZK60 magnesium alloys. Scanning electronic microscope (SEM) was employed for observation of fractography. Experimental cavity radius and volume fraction were determined by optical microscopy and corresponding picture-based analysis software. It is found that, the fractured surfaces after a superplastic elongation have a mixed characteristic of intergranular cavities and dimples. Further, the cavity growth is identified to follow a exponentially increasing mode.

Abstract: The cavity growth behavior in a polycrystalline LSI conductor is investigated on the basis of diffusion along grain boundary (GB) and interface (IF) induced by stress and electric current. The of GB and IF, which strongly affects the characteristics of the atom migration. Numerical analysis is conducted for a polycrystalline conductor with GB/IF network after a discussion on a specialized FEM for the diffusion. Results obtained are as follows. (i) In a conductor, the atom migration is eminently activated near a cavity along GBs while there is little flow without the defect. (ii) IF diffusion between the conductor and the surrounded passivation activates the atom migration along GBs inside of a conductor. This implies that the cavity grows under the interaction between GB diffusion and IF one. (iii) Under an external stress, the cavity growth is fast in the early stage while it is decelerated by the constraint of the triple junction ahead of the cavity. (iv) The complex branches of the atom migration due to electric current (EM) amplifies the stress evolution and the stress-induced atom migration (SM) takes place. The cavity grows under the interaction between EM and SM, which stems from the GB/IF network.