Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-Boron Carbide Ceramics

Author

Eric W. Neuman, Missouri University of Science and TechnologyFollow
Greg Hilmas, Missouri University of Science and TechnologyFollow
William Fahrenholtz, Missouri University of Science and TechnologyFollow

Abstract

The processing, microstructure, and mechanical properties of zirconium diboride-boron carbide (ZrB₂-B₄C) ceramics were characterized. Ceramics containing nominally 5, 10, 20, 30, and 40 vol% B₄C were hot-pressed to full density at 1900 ⁰C. The ZrB₂ grain size decreased from 4 to 2 μm and B₄C inclusion size increased from 3 to 5 μm for B₄C additions of 5 and 40 vol% B₄C, respectively. Elastic modulus decreased from 525 to 515 GPa and Vickers hardness increased from 15 to 21 GPa as the B₄C content increased from 5 to 40 vol%, respectively, following trends predicted using linear rules of mixtures. Flexure strength and fracture toughness both increased with increasing B₄C content. Fracture toughness increased from 4.1 MPa m^1/2 at 5 vol% B₄C to 5.3 MPa m^1/2 at 40 vol% B₄C additions. Flexure strength was 450 MPa with a 5 vol% B₄C addition, increasing to 590 MPa for a 40 vol% addition. The critical flaw size was calculated to be ~30 μm for all compositions, and analysis of the fracture surfaces indicated that strength was controlled by edge flaws generated by machining induced sub-surface damage. Increasing amounts of B₄C added to ZrB₂ led to increasing hardness due to the higher hardness of B₄C compared to ZrB₂ and increased crack deflection. Additions of B₄C also lead to increases in fracture toughness due to increased crack deflection and intergranular fracture.

Recommended Citation

E. W. Neuman et al., "Processing, Microstructure, and Mechanical Properties of Zirconium Diboride-Boron Carbide Ceramics," Ceramics International, vol. 43, no. 9, pp. 6942 - 6948, Elsevier Ltd, Jun 2017.

The definitive version is available at https://doi.org/10.1016/j.ceramint.2017.02.117

Department(s)

Materials Science and Engineering

Keywords and Phrases

Boron carbide; Hot-pressing; Mechanical properties; UHTC; Zirconium diboride; Ceramic materials; Cracks; Fracture; Microstructure; Vickers hardness; Zirconium compounds; Boron carbide ceramics; Crack deflections; Critical flaw size; Fracture surfaces; Intergranular fracture; Sub-surface damage

International Standard Serial Number (ISSN)

0272-8842

Document Type

Article - Journal

Document Version

Citation

File Type

text

Language(s)

English

Rights

© 2017 Elsevier Ltd, All rights reserved.

Publication Date

01 Jun 2017