Effects of ZrC content on the microstructure and mechanical property of ZrC/ZTA composites consolidated by hot pressing

Abstract In the present work, effects of ZrC addition (10, 15, 20, 25 vol%) on microstructure and mechanical properties of ZTA20mol% (Zirconia-20mol% Toughened Alumina) ceramic composites were investigated. Samples were prepared by Hot Pressing Sintering (HP) at 1 600 ℃ and 30 MPa for a soaking time of 2 hours. Microstructures were characterized by XRD, Raman, SEM and TEM. XRD and Raman spectra results revealed that only ZrC, α-Al2O3 and ZrO2 were detected for all composites, indicating that these ceramic composites had excellent chemical compatibilities. SEM images showed refined microstructure was obtained, and the fracture surfaces exhibited a mixed process of transgranular and intergranular fracture. According to the TEM observations, some nano-sized ZrC particles dispersed inside Al2O3 grains and formed an intra/inter-type nanostructure. The relative densities and Vickers hardness were inversely proportional to ZrC content, which gradually decreased from 98.24% to 94.89%, from 1 847 to 1 691 HV1, respectively. Flexural strength and fracture toughness were tested by three-point bending method and single-edge notched beam method, respectively. The fracture toughness increased at first and then decreased with ZrC content increased from 0 to 25 vol%. The maximum value was 11.23 MPa.m1/2 with 20 vol% ZrC addition, with an enhancement of 51% compared to the undoped ZTA mixture. The flexural strength, with a maximum of 1 121 MPa without ZrC addition and decreased to 645MPa with ZrC-10(vol%) addition, then increased monotonously to 1084 MPa as the ZrC content increased from 10 to 25 vol%.