Fig. 6: Mechanical properties and crack propagation behavior.
From: Superhard bulk high-entropy carbides with enhanced toughness via metastable in-situ particles
a Sketch and photograph showing the geometry of the specimens for fracture toughness measurement using the single edge notched beam (SENB) method. b SEM image of a representative Vickers indentation of the HEC sintered at 50 MPa with a load of 49 N. The annotation “c/a < 2.5” (c is the radius of crack and a is the half diagonal of the Vickers indent) in (b) indicates the suitability of using the Palmqvist crack model for evaluating fracture toughness of the present HECs. c Fracture toughness versus Vickers hardness values for the HECs in the present study, and the previously reported HECs19,24,33,42,43,44, as well as that estimated from the rule of mixture (ROM). The Vickers hardness values plotted in the diagram for the present HECs were measured under a load of 9.8 N. d–f High magnification SEM images of (WTaNbZrTi)C HEC sintered at 50 MPa, showing the crack propagation behavior. g Enlarged image of the region marked by the white rectangle in (b), displaying the main crack tip. h Fracture morphologies of the HEC sintered at 30 MPa after compressive testing at room temperature. i Fracture morphologies of the HEC sintered at 50 MPa.
