R-curve behavior, mechanical properties and microstructure of sintered ZrB2–SiCp–ZrO2f ceramics

In this paper, zirconium diboride based ceramics added with 20 vol.% silicon carbide particle and 15 vol.% zirconia fiber (Z20Sp15Zf) were prepared by hot-pressing at 1850 °C for 60 min under a uniaxial load of 30 MPa in Ar atmosphere. R-curves for Z20Sp15Zf ceramics were studied using the indentation-strength in bending technique and the envelope method. The results indicated that these two testing methods were consistent and viable for estimating R-curve. Z20Sp15Zf ceramics had high resistance to crack growth and damage tolerance with the 6.8 MPa m1/2 of steady-state toughness. The toughening mechanism was fiber debonding, fiber pull-out, crack bridging, crack branching, crack deflection and transformation toughening.