Design and preparation of high-performance dissolvable in-situ (MgO-Al3Fe)/AZ91 magnesium matrix composites by controlling the content of precursor particles combined with low-temperature extrusion

In this work, (MgO-Al3Fe)/AZ91 magnesium matrix composites with varying precursor (Fe3O4) content were fabricated by liquid in-situ preparation technology combined with low-temperature extrusion. After that, the influence of precursor content on the microstructure, mechanical and dissolvable properties of the as-extruded (MgO-Al3Fe)/AZ91 magnesium matrix composites was investigated. The results indicated that an increase in precursor content caused the average size of in-situ particles in the composites to first increase and then decrease, however, the grain size did not change much. After hot extrusion, the in-situ particle distribution improved, and grain refinement was significant. The dynamic recrystallization (DRX) process of the composites was realized by particle stimulation nucleation (PSN) and continuous dynamic recrystallization (CDRX) mechanisms. The final as-extruded 1 % composite had the highest volume fraction of dynamic recrystallization and the finest grains, while the as-extruded 0.5 % composite was the opposite. The strain hardening rate at the early strain stage and the possibility of occurring multi-system slip increased in the as-extruded 1 % composite relative to the as- extruded 0.5 % composite, leading to the high strength and good ductility of the as-extruded 1 % composite. The galvanic corrosion degree increased with precursor content, resulting in higher dissolution rates and weight loss rates, and a shift in corrosion morphology from fine banded to severe local corrosion. The high strength and high dissolution rate of the as-extruded composites are attributed to the synergistic effects of coupled MgO and Al3Fe particles and low-temperature extrusion.