Microstructure Evolution of Al-0.35%Si-0.2%Mg-0.3%Ce Alloy During Hot Extrusion and Its Contributions to Performances

Microstructure evolution of Al-0.35 wt.%Si-0.2 wt.%Mg-0.3 wt.%Ce alloy during hot extrusion and its contributions to mechanical properties and conductivity are investigated in this paper. Results show that, with a significant deformation (an extrusion ratio of 36), complete recrystallization occurs at the extrusion temperature ranging from 460 to 560 °C, and the grain size is increased only slightly with the temperature. However, when the rod is extruded at 510 °C with a small ratio of 16, only local and incomplete recrystallization occurs, and the grain structure is highly non-uniform. With the same large deformation (a ratio of 36), the rod extruded at 460 °C has the lowest strength. The severely occurred dynamic precipitation of Mg₂Si phase is responsible for it. For the rod extruded at 510 °C with the small deformation (a ratio of 16), the highly non-uniform grain structure leads to a considerably reduction in all indexes of tensile properties. It is found that the conductivity of samples with the same ratio of 36 is decreased considerably with the extrusion temperature. The combined effects of the dynamic precipitation and lattice vacancy population on lattice distortion are responsible for it. In the rod extruded at 510 °C with the small ratio of 16, the retained large number of dislocations and sub-grains leads to a significant reduction in conductivity, compared to the one with the large ratio of 36. An excellent combination of strength and conductivity could be obtained by extruding at 510 °C with a ratio of 36. In this case, uniform and completely recrystallized grain structure is produced.