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Achieving Superhardness and Enhanced Toughness in High-Entropy Boride-Based Composites by Tailoring Their Multi-Scale
Shuaihang Qiu1,2, Ji Zou1,2, Jingjing Liu1,2
1State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan, 430070, China.
Small (Weinheim an Der Bergstrasse, Germany)
|February 7, 2025
Summary
High-entropy ceramics with poor strength were improved using a novel B4C composite. This material exhibits superior hardness and fracture toughness due to its unique hierarchical microstructure.
Area of Science:
- Materials Science
- Ceramic Engineering
- Nanotechnology
Background:
- High-entropy alloys offer strength and toughness, but high-entropy ceramics typically lack these properties, exhibiting only hardness.
- Developing high-entropy ceramics with enhanced mechanical properties is crucial for advanced applications.
Purpose of the Study:
- To design and fabricate a novel B4C-(Zr0.2Hf0.2Nb0.2Ta0.2Ti0.2)B2 composite with a hierarchical microstructure.
- To investigate the mechanical properties, including hardness, flexural strength, and fracture toughness, of the designed composite.
- To elucidate the microstructural features and deformation mechanisms responsible for the enhanced properties.
Main Methods:
- Boronizing reaction sintering of dual-phase multicomponent carbides.
- Microstructural characterization using transmission electron microscopy.
- Mechanical property testing, including Vickers hardness, flexural strength, and fracture toughness measurements.
Main Results:
- The B4C-(Zr0.2Hf0.2Nb0.2Ta0.2Ti0.2)B2 composite exhibited a unique hierarchical microstructure with platelet-like aggregations of core-rim structured (Zr0.2Hf0.2Nb0.2Ta0.2Ti0.2)B2 grains in a B4C matrix.
- The composite achieved a high flexural strength of 633 ± 25 MPa and a fracture toughness of 4.70 ± 0.08 MPa m1/2, attributed to crack bridging and fine-grained microstructures.
- Unparalleled Vickers hardness exceeding 54 GPa at 1.96 N was observed, resulting from the homogenization of core-rim structured diboride grains and difficult lattice glides.
Conclusions:
- The designed B4C-(Zr0.2Hf0.2Nb0.2Ta0.2Ti0.2)B2 composite successfully overcomes the limitations of traditional high-entropy ceramics.
- The hierarchical microstructure and specific deformation mechanisms are key to achieving excellent comprehensive mechanical properties.
- This study provides a new strategy for designing high-performance high-entropy ceramics through multi-scale microstructure tailoring and composition tuning.
