Chemical reactivity in materials science: from the thermodynamic rules to enhanced materials development.

In the field of materials science, chemical reactivity poses a significant challenge. It becomes a critical issue when synthesizing homogeneous materials (such as alloys, ceramics, etc. ) or during assembly processes (e.g., brazing, welding). It also plays a crucial role in the performance of materials and assemblies under thermal, mechanical or environmental stresses. The first objective of this talk is to remember that chemical reactivity is governed by thermodynamics. The impact of chemical reactivity on materials and the tools available to understand it: phase equilibria and the concept of diffusion path, will be presented and discussed, with illustrative examples including the brazing of titanium alloy and ceramics components [1], as well as the reactivity between Boron and Silicon Carbide [2]. The second objective of this talk is to highlight how chemical reactivity can be leveraged as an advantage in material synthesis, specifically for developing advanced Metal Matrix Composites (MMCs). By understanding phase equilibria and non-equilibrium states, chemical reactivity can be transformed as an innovative solution to synthesize both the matrix and the reinforcements of MMC in situ, addressing traditional challenges in MMC synthesis like interphase formation or interface contamination. The proof of concept focused on Al-based MMC reinforced with ceramic particles (TiC, TiB2, etc..) will be detailed from a thermodynamic perspective. The talk will conclude with ongoing research on new Al-based composites reinforced with alumino-boron carbide phases, highlighting the potential for innovative materials through controlled chemical reactivity. [1] J. Andrieux, O. Dezellus, F. Bosselet and J.C. Viala (2009): Low-temperature interface reaction between titanium and the eutectic silver-copper brazing alloy, J Phase Equilibria Diffus 30(1), 40-45. [2] Y. Benamra, B. Gardiola, F. Robaut, O. Dezellus, F. Cauwet, L. Auvray, G. Ferro, J. Andrieux (2025): Boron-SiC Diffusion Couple: Thermodynamics and Reactivity at High Temperature, J Phase Equilibria Diffus 46, 495-510.