Constructing Reaction-Limited and Robust Interface in 2D MAB-Phase MoAlB Nanosheet-Reinforced Copper Matrix Composites

MoAlB, a MAB phase, exhibits significant potential as a reinforcement material for copper matrix composites due to its exceptional overall properties. However, its application is limited by the tendency to decompose at elevated temperatures during processing, leading to fragmentation and a reduction in the copper matrix's electrical conductivity. Addressing this challenge, this study successfully prepared two-dimensional (2D) MoAlB nanosheets (NSs) via viscous-solvent-assisted ball milling. Subsequently, these nanosheets were employed as reinforcement to fabricate MoAlB NSs/Cu composites through an impregnation-reduction-sintering route. Characterization of the resulting composite revealed a limited interfacial reaction between the 2D MoAlB NSs and the copper matrix, leading to the formation of a distinctive gradient interface structure. The gradient interface consists of a Cu/MoB atomic-scale composite transition zone and a Mo₂AlB₂/Cu semicoherent interface. This reaction-limited and robust interface synergistically activates multiple strengthening mechanisms, including significant grain refinement, efficient load transfer, and dislocation strengthening. Moreover, this structure effectively mitigates solute atom electron scattering in the copper matrix by constraining Al atom diffusion to the interfacial regions. Consequently, the 0.5 wt % MoAlB NSs/Cu composite achieved a notable balance of mechanical and electrical properties: a tensile strength of 333.3 MPa, which represents a significant improvement over pure Cu (255.1 MPa) and the 0.5 wt % MoAlB/Cu composite (268 MPa), combined with an elongation of 15.5% and an electrical conductivity of 92.6% IACS. Additionally, the composites demonstrated superior resistance to high-temperature softening, retaining high hardness even after annealing at 900 °C. These findings present a new design strategy for creating next-generation high-performance metal matrix composites.