Anisotropic slip activation via homogeneous dislocation nucleation in ZrB2 ceramic grains during nanoindentation.

Anisotropic dislocation nucleation of differently oriented zirconium diboride (ZrB 2 ) grains in a polycrystalline ZrB 2 -based ceramic composite was investigated during nanoindentation with a Berkovich tip. Based on the Hertzian stress analysis of the measured strain bursts, the critical resolved shear stresses for slip systems of 10 1 ¯ 0 11 2 ¯ 0 , 10 1 ¯ 0 0001 and 10 1 ¯ 0 11 2 ¯ 3 types were determined. Homogeneous dislocation nucleation was revealed with near theoretical critical resolved shear stress (~35 GPa) for each slip system. The analysis of the orientation dependence of the calculated maximal resolved shear stress values inferred anisotropic dislocation nucleation in ZrB 2 grains with single and simultaneous activation of the investigated slip systems. [ABSTRACT FROM AUTHOR]