Evading strength and toughness trade-off in graphene reinforced Nb/Nb5Si3 composites

Abstract

The Strength and toughness trade-off is a long-term dilemma in structural materials. Here, we report a new strategy for synergistically improving the strength and toughness of Nb/Nb5Si3 composites by incorporating high-performance graphene to tailor the interfacial coherency and strengthen the matrix. The fabricated graphene reinforced Nb/Nb5Si3 composite stands out from available reports on Nb/Nb5Si3 composites. The medium mismatch Nb–Nb5Si3 interface is transformed into the low mismatch Nb–Nb4C3–Nb5Si3 multi-interfaces because of the incorporation of graphene and the formation of nano-sized interfacial Nb4C3 phases. These low mismatch interfaces facilitate the multiplication of dislocations and the formation of long-range dislocations to annihilate, thereby leading to a superior combination of strength and toughness. Importantly, the low mismatch of Nb4C3–Nb and -Nb5Si3 interfaces are beneficial for forming a strong interfacial bonding and effectively promoting the anchoring effect to inhibit the pull-out of graphene, resulting in increasing the load transfer from matrix to graphene. The deflecting and bridging of cracks, as well as microcracks, are recognized as the toughening mechanisms in this composite. The present study reveals a strategy to evade the strength and toughness trade-off in Nb/Nb5Si3 composites by incorporating high-performance graphene to tailor the interfacial coherency and strengthen the matrix.