Experimental Study on Preparation and Properties of Zirconium Boride Reinforced NbMo-matrix Composites

Zirconium boride reinforced NbMo-matrix composites with composition of 42.5%Nb+42.5%Mo+15%ZrB2 (vol%) and 42.5%Nb+42.5%Mo+10.5%ZrB2+4.5% SiC (vol%) were fabricated by hot-pressing under an uniaxial load of 30 MPa at 1600 °C in Ar atmosphere with holding time of 1 h and 2 h. The microstructure and phase composition were analyzed by SEM, EDS and XRD. The mechanical properties were measured by Micro Vickers and hydraulic universal tester. Results show that small ZrB particles are distributed uniformly in NbMo solid solution. Residual SiC and formed MoSi2 are found in the samples with SiC. The compressive strength is improved to 1974.17 MPa from 1380.15 MPa of the NbMo solid solution. The yield stress is improved to 1664.13 MPa and the hardness is 3∼5 times higher than that of NbMo. The longer holding time (2 h) leads to the higher strength, yield stress and hardness. The increase in strength and hardness of the composites is a consequence of the solid solution strengthening mechanism and the excellent interface bonding between ZrB and Nb-Mo solid solution.