Influence of the heat treatment on the precipitation of the intermetallic phases in commercial AlMn1FeSi alloy

In this paper results of the microscopic examinations (LM, SEM) of the heat treatment effect on the morphology and chemical composition of the intermetallic phases containing transition metals Fe and Mn in the AlMn1FeSi alloy have been presented. By means of the EDS X-ray microanalysis the chemical composition of the observed intermetallic phases was estimated The polyhedra of the Al6FeMn phase of ratio Fe:Mn <1 were recognised to be the primary precipitates in the intermetallic phase formation sequence in the liquid state. In the residual liquid the rod-like shape of the Al6FeMn particle have formed at lower temperature. In these microregions the processes of the quaternary α-AlFeMnSi phase formation started to develop during alloy solidification as well as after heat treatment. The α-AlFeMnSi phase origin at the α-Al/Al6FeMn interface was revealed by means of the SEM observation of the deep etched specimens. The temperature and the mechanism of this phenomenon in the solid state were identified by means of the microscopic observations and DSC analysis. The changes in the chemical composition (relative concentrations of the transition metals Fe, Mn and Si) of the α-AlFeMnSi phase occurring during the heat treatment were related to the activation of the short circuit diffusion of the transition metals Fe and Mn along the interface α-Al/Al6FeMn/α-AlFeMnSi.