Strengthening Tungsten Diboride toward a Superhard Material by Ordered Vacancy Pairs

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• Tungsten diboride (WB_{2+x}) is theoretically a superhard material.
• Its practical application is limited by low toughness due to unfavorable dislocation slip systems.

Purpose of the Study:

• To enhance the toughness and hardness of tungsten diboride (WB_{2+x}).
• To investigate the role of ordered atomic vacancies in improving mechanical properties.

Main Methods:

• Synthesizing rhenium-doped tungsten diboride ((W_{0.9}Re_{0.1})_{1-δ}B_{2+x}) under high pressure.
• Characterizing the material structure and identifying the location of atomic vacancies.
• Measuring mechanical properties including hardness and toughness.

Main Results:

• Ordered metal-vacancy pairs were introduced in WB_{2+x} via rhenium doping.
• These vacancies predominantly reside in the {210} and {102} planes, enhancing dislocation mobility.
• Achieved a load-invariant superhardness of approximately 40 GPa with improved toughness and plasticity.
• Demonstrated significantly enhanced thermal stability, comparable to cubic boron nitride (cBN).

Conclusions:

• Experimentally realized a superhard tungsten diboride material.
• Tailoring atomic deficiencies is an effective strategy for improving the mechanical properties of transition-metal diborides.
• Ordered vacancies enhance dislocation mobility, leading to superhardness and improved toughness.