The reinforcing mechanism of ionic interdiffusion on MgO-MgAl₂O₄ composites between structural densification and mechanical property

MgO-MgAl2O4 composites are arising as promising candidates for high-temperature industrial applications. For this reason, the in -situ synthesis of such types of composites with spinel structure has attracted the attention of the scientific community. Along these lines, in this work, magnesia and bauxite were used as raw materials to fabricate MgAl2O4 composites. The mass proportion in the composites was also adjusted by using the solid-phase sintering method at 1400-1650 C-degrees to enhance its mechanical properties and densification. XPS and SEM measurements were conducted, indicating that the MA50 sample with the mass ratio of 50:100 (MgAl2O4:MgO + MgAl2O4) exhibited the best properties at 1550 C, in terms of uniformity of the grains' growth morphology, optimal densification of the matrix structure, and achieving a maximum flexural strength of 113.23 MPa. From our analysis, it was demonstrated that the non-equivalent displacement of Al3+ and Mg2+ could easily lead to the formation of the (Mg(1-x)Alx/2)Mgx/4O solid-solution during the similar crystal structure, which enhanced mechanical strengthening between the micro-grain and framework. Meanwhile, the existence of a certain liquid phase not only effectively increased the mass transfer during the processing of interdiffusion between Al3+ and Mg2+, but also promoted the distribution of crystallite and microstructure.