Mechanical and thermal properties of ZrC/ZTA composites prepared by spark plasma sintering

Abstract

In the present work, the influence of sintering temperature and particle size of pristine ZrC particles on the microstructure, mechanical properties, and thermal properties of ZrC/ZTA ceramic composites are investigated. Specimens consolidated by spark plasma sintering at different sintering temperatures from 1500 °C to 1800 °C. XRD results revealed that α-Al2O3, t-ZrO2, ZrC, and a small quantity of m-ZrO2 phases are present in the composites. The microstructure of μm-ZrC/ZTA is found to be more compact than nm-ZrC/ZTA composites. There is an apparent increase in the average grain size with the increase in temperature. From the micrographs of fracture surfaces, step-wise transgranular fracture structures are observed. Relative densities and Vickers hardness are in proportion to sintering temperature from 1500 °C to 1700 °C. The maximum Vickers hardness of 1919 HV1 is obtained for μm-ZrC/ZTA composites. Indentation fracture toughness displays a gradual rise when the temperature rises from 1500 °C to 1700 °C, then deteriorates at 1800 °C for both nm-ZrC/ZTA and μm-ZrC/ZTA ceramic composites. The maximum fracture toughness values for nm-ZrC/ZTA and μm-ZrC/ZTA are 6.75 MPa m1/2 and 6.83 MPa m1/2, respectively. The thermal conductivity of the specimens decreased gradually as the temperature increases from 100 °C to 1000 °C. The obtained results indicated that the 1700 °C is the optimized sintering temperature where μm-ZrC/ZTA composites have excellent performance on microstructure, mechanical properties, and thermal properties than nm-ZrC/ZTA composites.