Inhomogeneity of mechanical properties and deformation instabilities in Al-Cu-Li-Mg alloy

Extrusions of complex Al-Li-based alloys often exhibit a strong dependence of mechanical properties on the position of specimens inside the extruded profiles. This paper deals with mechanical testing and electrical resistivity measurements performed on profiles of Al-Cu-Li-Mg alloy with the cross section of the dumb-bell shape, i.e. of a complicated shape, where the inhomogeneity of mechanical properties through the profile is very pronounced. The extruded profiles were exposed to the solution heat treatment and to the subsequent natural or artificial ageing. The specimens were mechanically tested with a constant stress rate at room temperature and exhibited jerky flow with the critical strain for the onset of serrations depending on the position inside the profile. These results support our point of view that the inhomogeneity of mechanical properties reflects an inhomogeneity of precipitation processes due to the persisting inhomogeneity of the structure (i.e. the grain size and the fibre structure of grains).