Simultaneously enhancing strength and ductility in boron nitride nanosheets reinforced TA15 composites via gradient reinforcement distribution

The simultaneous increase of strength and ductility in titanium matrix composites (TMCs) has always been a substantial challenge. In this study, high performance boron nitride nanosheets reinforced TA15(BNNSs/TA15) composites were fabricated by gradient reinforcement distribution strategy. The intrinsic structure of BNNSs was well preserved and TiB on partly reacted BNNSs resulted in a spectacular interface bonding and BNNSs intrinsic strengthening, and the distribution of TiB@BNNSs within the composite samples exhibits a gradient pattern, defined by a steady decrease from the surface to the interior. Tensile tests reveal that the composites maintain high strength while exhibiting superior tensile ductility. Compared to the TA15 matrix, the ultimate tensile strength(UTS) and uniform elongation(E_u) of the composites increased by 11.63 % and 29.32 %, respectively, demonstrating a significant synergistic effect on strength and ductility. Furthermore, the back stress strengthening effect, caused by the non-uniform distribution of reinforcements and the activation of <c+a> dislocations in the ultrafine grains close to the reinforcements, endows the composites with high strain hardening capability. This work offers a new path for the preparation of high performance TMCs.