Title : Reconstruction of dislocation core structures for aluminum
Abstract:
Dislocations are the main carrier of plasticity in crystalline materials and their behaviour has strong consequences in the mechanical response of materials. The concept of the dislocation as a line defect was proposed in 1930’s to explain the discrepancy between the theoretical shear strength of a perfect crystal and the experimentally measured yield strength and the work-hardening phenomenon, i.e., a crystal that has been deformed plastically requires a greater stress to deform further. However, the remarkable achievements so far in dislocation analysis, observation and simulation have not led to a clear and full understanding of dislocation behaviour. The current level of dislocation knowledge is not much different from that described by Cottrell in 1953. One of the fundamental problems is that the basic model of dislocations that have been adapted in all analyses is based on the atomic configuration for a simple cubic crystal. All simulations fail to construct a 3D supercell containing a properly defined dislocation line. The matter is that most metals possess a close packed crystal structure and the dislocation core structures are therefore substantially different from that for a simple cubic crystal. In the present work, the core structure of {111}<110> dislocations is reconstructed using crystal visualization software for the first time, showing substantially different crystallographic features from those generally perceived. The possible decomposition of this core structure is discussed and the line tension and stress field in association with this core structure is analysed as well.
