Abstract
The influence of microstructure on crack propagation was studied for three different Al-Zn-Mg-Cu alloys with similar tensile properties. A pronounced effect of microstructure was found for fatigue conditions as well as for rising load conditions. The micromechanisms of crack propagation were studied fractographically. The main emphasis was on the investigation of the plastic zone ahead of the crack tip by transmission electron microscopy (TEM). In all cases, the TEM investigations revealed the same crack-propagation mechanisms as found in the fractographic examinations. By a comparison with deformed tensile specimens the strain distribution in the plastic zone could be evaluated. This analysis showed a very narrow region of high plastic deformation followed by a long-range zone of low deformation.
Get full access to this article
View all access options for this article.