Observations and calculations on mechanical anisotropy and plastic flow of an AlZnMg extrusion

An extruded plate of the alloy AA7108 has been characterized using texture analysis and uniaxial tensile tests. The yield surface, directional yield stresses and plastic strain ratios are calculated from Taylor-Bishop-Hill analysis, employing the measured texture data in combination with either the full constraints model or a relaxed constraints model. Three phenomenological yield functions, capable of describing yield anisotropy, are compared by means of their ability to reproduce the shape of the crystallographic yield surface and to predict directional properties, i.e. R-values and yield stress. On the basis of experiments and calculations it has been found that the Taylor relaxed constraints model describes the present material more consistently with respect to experimental findings than the Taylor full constraints model. Copyright (C) 1996 Acta Metallurgica Inc.