Effect of pre-precipitation on microstructure and mechanical properties of extruded Mg-Sn-Zn alloys

Effect of pre-precipitation on the microstructure and mechanical properties of extruded Mg-1.1Sn-2Zn alloy (at%) has been investigated in this study. The result shows that the presence of a high density of precipitates before extrusion is very effective in obtaining a fine dynamic recrystallized grain structure. The extrusion of the alloy without precipitates results in a bimodal grain structure with fine grains: ∼5 μm-size fine grains and ∼15 μm-size coarse grains. On the contrary, the extrusion of the alloy with a high density of precipitates results in a ∼2 μm-sized, fully dynamic recrystallized grain structure exhibiting a better combination of mechanical properties. The fine precipitates sheared during extrusion act as nucleation sites for DRX and prevent grain growth because of the pinning effect. This study shows that the aging treatment before extrusion is very effective in obtaining a homogeneous and fine grain structure exhibiting a better combination of mechanical properties.