In-situ solid-state synthesis of Mg₂Si/MgO/Mg composites

Mg₂Si/MgO dispersoids reinforced Mg matrix composites (Mg₂Si/MgO/Mg) were successfully In-situ solid-state synthesized by using Mg-SiO₂ powder mixture on the route of preheating and hot forging. Results indicate that SiO₂ can completely react with Mg and form Mg₂Si/MgO dispersoids by preheated at 853 K for 240 s, and fully densified Mg₂Si/MgO/Mg composites can be achieved by hot forged at 573 K under the pressure of 880 MPa. A method was proposed to calculate the reactive heat for forming Mg₂Si/MgO dispersoids. It equals 705 kJ, implying that Mg can easily deoxidize SiO₂. The synthesized Mg₂Si/MgO dispersoids are inhomogeneous in size and shape when the initial powder mixture is conventionally cold compacted. On the other hand, the repeated plastic working (RPW) process not only improves the morphologies of Mg₂Si/MgO dispersoids but also decreases their synthesizing temperature. The mechanisms which are responsible for the microstructural improvement and the decrease in the synthesizing temperature are the refinement of SiO₂ particles and the breakage of MgO films on the surface of MR particles.