Thermally activated movement of screw dislocations in polygonized aluminum

Abstract

In this paper, we study the evolution of polygonized dislocation structures and make an analysis of plastic deformation mechanisms under creep conditions at high temperatures in polygonized aluminum of 99.3% purity. Dislocations play a role of vital importance in the evolution of plastic deformation. The influence of dislocations on the σ – ε curve behavior as well as the shape of this curve have not yet been understood and explained. The absence of such understanding remains a problem nowadays. It is necessary to find and describe an important relationship between dislocation structures studied by means of Transmission Electron Microscopy (TEM) imag es under static conditions, the values for the yield strain, resistance to deformation, and the fracture limit. Concerning this relationship, it is relevant to mention here that the mechanical and thermal stability of defects at the sub-structural hardening drastically determines the stability of the polygonized structure under working conditions. Keeping in mind that polygonized structures are generated as a result of a thermo-mechanical treatment or directly under creep conditions, it is natural to expect that the instabilities of such structures are to be observed under much more stringent temperature and load conditions than those under which these structures were formed.

Keywords

• HVTEM
• polygonization
• creep
• dislocations
• structure
• in situ study