Synthesis and corrosion resistance of solid solution Ti3(Al1−xSix)C2

Highlights: • Ti₃Al_1−xSi_xC₂ can form a complete solid solution through hot pressing sintering. • Solid solution hardening effect enhances the hardness of Ti₃Al_1−xSi_xC₂. • Si addition differs expansion on the lattice parameter, showing strong anisotropy. • Si addition affects passive films and corrosion resistance. -- Abstract: Solid solutions Ti₃(Al_1−xSi_x)C₂ (x = 0–1) were successfully fabricated by hot pressing with the powder mixture Ti/Al/TiC/Si. The difference on variations between the linearly decreased c-lattice parameter and the nearly constant a-lattice parameter suggested the strong anisotropy of MAX phase lattices. Vickers hardness increased after Si addition due to the solid solution hardening effect brought by Al-Si alloying in the A sites, reached the maximum at 504.46 Hv of Ti₃Al_0.4Si_0.6C₂, and slightly decreased because of the increased grain size. All Ti₃(Al_1−xSi_x)C₂ solid solution passivated in 3.5% NaCl solution with the N-type-semiconductor-feature passive films formed on the surface. With the increasing Si addition, the increased resistance of charge transfer and the reduced corrosion current density implied the increased corrosion obstruction and performance. With the increase in Si addition, the content of SiO₂ in the passive films increased, and the donor carrier concentration reduced, thereby enhancing the corrosion resistance. Accordingly, the corrosion difficulty and resistance were enhanced.