Microstructure and local crystallographic evolution in an Al-1 wt% Mg alloy deformed at intermediate temperature and high strain-rate

The deformation processes occurring in an Al-1 wt% Mg alloy of commercial purity have been studied using plane strain compression (PSC). As part of a matrix of tests covering a range of temperatures and strain rates experienced in industrial hot rolling, the combination T = 305 degrees C and epsilon over dot = 25 s(-1) has been studied in detail. This is near the top of the possible range for the Zener-Hollomon parameter, Z, in hot rolling. Experimental measurements of cell size, misorientation between cells and dislocation density were obtained as a function of strain. The qualitative interpretation of the microstructure was enhanced by the judicious use of both optical and transmission electron microscopy. The observations in this paper illustrate the complexity of the evolution of microstructure with strain, and also how important microstructural features (such as the lamellae of dislocation cells) can be overlooked. In spite of the complexity, there is a striking degree of self-similarity in the microstructure over a wide range of strain. The frequency distributions of cell size, or misorientation across different categories of boundary, essentially change very little with respect to their mean values. Copyright (C) 1996 Acta Metallurgica Inc.