A comparative study of Mg–9Al–3Si high silicon magnesium alloy extruded from rapid solidification strip and conventional ingot casting processes

The low yield strength of magnesium alloys is one of the main reasons that seriously affect their applications. It is also difficult to exceed 1 % for the silicon content of traditional magnesium alloys. It is entirely possible to solve these problems by using rapid solidification (RS) to implement grain refinement and solubility expansion of alloying elements. This study compares the microstructure and mechanical properties of Mg–9Al–3Si high-silicon magnesium alloy extruded from RS strips (as-RS) and conventional casting ingots (as-cast). After remelting the Mg–9Al–3Si ingot, a large amount of 30 μm thick strips was prepared using the single-roll melt-spinning method, and then the strips were crushed into small particles. Subsequently, after the particles underwent hot pressing and two stages of hot extrusion , the as-RS extruded Mg–9Al–3Si rod achieved tensile yield strength of 354 MPa, ultimate tensile strength of 406 MPa, elongation of 11 % and compressive yield strength of 360 MPa, which are 43 %, 29 %, 252 % and 40 % higher than that of as-cast extruded Mg–9Al–3Si rod. The improvement in the mechanical properties of Mg–9Al–3Si as-RS extruded rod is attributed to the ultra-fine 1.25 μm α-Mg matrix grains, the fine and dispersed second-phase particles of Mg 2 Si and β-Mg 17 Al 12 . Furthermore, the noticeable alleviation of the tension-compression asymmetry in the as-RS extruded Mg–9Al–3Si rod benefits from the reduced texture and decreased twinning due to grain refinement. • The Mg–9Al–3Si alloy has a yield strength of 354 MPa and an elongation of 11 %. • The superior Mg–9Al–3Si alloys can be prepared by rapid solidification and extrusion. • Superior performance are attributed to grain refinement and second phase dispersion. • Reduced twinning and weakened texture eliminate tensile-compression asymmetry.