Mechanical property improvement of diffusion bonded ZrC_x joints by chemical homogenization using Ta as the interlayer

In the present study, a transition metal Ta foil was used as the interlayer to diffusion bond ZrC_x ceramics. A needle-like ζ-Ta₄C_3-x phase was initially formed at the interface and could be effectively dissolved into the base ceramic by reasonably tuning the bonding temperature and holding time, resulting in a chemically homogeneous joint when diffusion bonded at 1600 °C for 1 h under 20 MPa pressure. The composition of the homogeneous joints was composed of ZrC_x(Ta), which is very similar to the base ceramic. The ζ-Ta₄C_3-x phase was found beneficial to the mechanical property of the joints due to its mechanically interlocking effect and the ability to absorb the propagation energy of microcracks. The chemically homogeneous joint had comparable four-point bending strength and nano-indentation hardness with that of the base ceramic, indicating that chemical homogenization of the joint has great potential to enhance the mechanical property of the ZrC_x joints.