Modulation of Mechanical Properties in Ti3AlC2 via B Substitution and Charge-Compensation-Induced Carbon Vacancies

Abstract

Tuning the intrinsic bonding and mechanical behavior of MAX phases is crucial for tailoring their performance. In this work, a series of Ti3AlC2–xBx MAX phase ceramics were fabricated via spark plasma sintering, and we systematically investigated the effects of B substitution on their crystal structure, bonding characteristics, and mechanical properties through a combination of experiments and theoretical calculations. B substitution creates local electronic imbalance within the M–X layers, which in turn promotes carbon vacancy formation via charge compensation process. The interplay between B incorporation and Cv formation induces further structural relaxation and charge redistribution. As a result, the resistance to elastic failure and plastic deformation failure is enhanced by 27.6% and 76.0%, respectively, under the synergistic influence of M–X bonds and Cv. However, under high B concentrations, excessive Cv accumulation destabilizes the Ti3C2 layers and drives the formation of Ti2AlC. Overall, this work systematically unravels how B substitution modifies the Ti3AlC2 structure, offering valuable insights into the regulation of X-site chemistry and bonding in MAX phases.