Boron nitride nanosheets decorated with copper nanoparticles to achieve intrinsic strengthening and balanced tensile properties in titanium matrix composites

Boron nitride nanosheets (BNNSs) have been widely used to improve the mechanical properties of metal matrix composites (MMCs). However, their high chemical reactivity with titanium (Ti) during high-temperature processing often leads to severe interfacial reactions, which compromises the effective reinforcement efficiency of BNNSs in Ti matrices. In this study, BNNSs coated with copper (Cu) nanoparticles reinforcement (Cu@BNNSs) were designed as an interfacial regulation strategy via electroless plating method. The Cu@BNNSs were incorporated into the Ti matrix and processed using the field-assisted sintering technique (FAST) and subsequent hot rolling (HR). The Cu coating acted as a sacrificial layer that effectively minimized interfacial reaction between BNNSs and Ti, preserving the structural integrity of BNNSs within the matrix. Microstructural analysis revealed a distinct crystallographic orientation relationship: Ti₂Cu [3‾32]//α-Ti [011‾0], indicating a well-defined interface that reduced lattice strain and improved adhesion between the BNNSs and the Ti matrix. Tensile tests demonstrated a significant strength enhancement with balanced ductility, reaching up to 773 MPa when the composite contained only 0.05 wt% BNNSs, representing an increase of 47.5% compared to pure Ti. The superior mechanical properties of the Cu@BNNSs/Ti composite are mostly attributed to the high-efficiency load transfer capability of BNNSs, in-situ formed TiB_p and Ti₂Cu compounds. This study highlights the potential of metal-modified BNNSs reinforcements for designing high-performance Ti-based composites.