Room-temperature mechanical properties of a high-entropy diboride

The mechanical properties of a (Hf,Mo,Nb,Ta,W,Zr)B-2 high-entropy ceramic were measured at room temperature. A two-step synthesis process was utilized to produce the (Hf,Mo,Nb,Ta,W,Zr)B-2 ceramics. The process consisted of a boro/carbothermal reduction reaction followed by solid solution formation and densification through spark plasma sintering. Nominally, phase pure (Hf,Mo,Nb,Ta,W,Zr)B-2 was sintered to near full density (8.98 g/cm(3)) at 2000 degrees C. The mean grain size was 6 +/- 2 mu m with a maximum grain size of 17 mu m. Flexural strength was 528 +/- 53 MPa, Young's modulus was 520 +/- 12 GPa, fracture toughness was 3.9 +/- 1.2 MPa center dot m(1/2), and hardness (HV0.2) was 33.1 +/- 1.1 GPa. A Griffith-type analysis determined the strength limiting flaw to be the largest grains in the microstructure. This is one of the first reports of a variety of mechanical properties of a six-component high-entropy diboride.

Automated summary

The mechanical properties of a (Hf,Mo,Nb,Ta,W,Zr)B-2 high-entropy ceramic were characterized at room temperature. The ceramic exhibited high hardness, flexural strength, and fracture toughness.