Microstructure and Mechanical Properties of ZrC _x-NbC _y-Cu Composites by Reactive Infiltration at 1 300 °C

ZrC_x-NbC_y-Cu composites were fabricated by pressure-less reactive infiltration of Zr-Cu binary melts into porous NbC preforms at 1 300 °C. The effect of Zr content in the infiltrator on microstructure of the as-synthesized composites was studied. Mechanical properties of the composites were reported. A partial displacement of Nb atoms in NbC by Zr atoms from Zr-Cu melt occurs during the reaction between Zr-Cu melt and porous NbC preform. The formation of a core-shell structure suggests the reaction is mainly a dissolution-precipitation type. NbC dissolves into Zr-Cu melt, from which the (Nb,Zr)C_z phase precipitates and grows. With increasing Zr content in the Zr-Cu infiltrator, the reaction is enhanced and the infiltration is easily chocked. ZrC_x-NbC_y-Cu composite is synthesized using Zr₁₄Cu₅₁ infiltrator. The flexural strength and fracture toughness of ZrC_x-NbC_y-Cu composite reach 637 MPa and 12.7 MPa·m^1/2, respectively. And the improved toughness is probably attributed to residual Cu phase and plate-like Nb_xC_y phases.