First-principles prediction, fabrication and characterization of (Hf0.2Nb0.2Ta0.2Ti0.2Zr0.2)B2 high-entropy borides. Issue 12 (15th June 2022)

• Record Type: Journal Article
• Authors: Qiao, Linjing; Liu, Yi; Gao, Yu; Bi, Jianqiang; Li, Yonghan; Liu, Chen; Gao, Jian; Wang, Weili; Qian, Zhao
• Is Part Of: Ceramics international. Volume 48:Issue 12(2022)
• Page Start: 17234
• Page End: 17245
• Publication Date: 2022-06-15
• Subjects: First-principles calculations -- High-entropy boride -- Boro/carbothermal reduction -- Microstructure -- Mechanical properties; Ceramics -- Periodicals; Céramique industrielle -- Périodiques; Ceramics; Periodicals; Electronic journals; 666
• DOI: 10.1016/j.ceramint.2022.02.281
• Languages: English
• ISSNs: 0272-8842

Abstract

Abstract: The microstructure and mechanical properties of (Hf0.2 Nb0.2 Ta0.2 Ti0.2 Zr0.2 )B2 high-entropy boride (HEB) were first predicted by first-principles calculations combined with virtual crystal approximation (VCA). The results verified the suitability of VCA scheme in HEB studying. Besides, single-phase (Hf0.2 Nb0.2 Ta0.2 Ti0.2 Zr0.2 )B2 ceramics were successfully fabricated using boro/carbothermal reduction (BCTR) method and subsequent spark plasma sintering (SPS); furthermore, the effects of different amounts of B4 C on microstructure and mechanical properties were evaluated. Due to the addition of B4 C and C, all samples formed single-phase solid solutions after SPS. When the excess amount of B4 C increased to 5 wt%, the sample with fine grains exhibited superior comprehensive properties with the hardness of 18.1 ± 1.0 GPa, flexural strength of 376 ± 25 MPa, and fracture toughness of 4.70 ± 0.27 MPa m 1/2 . Nonetheless, 10 wt% excess of B4 C coarsened the grains and decreased the strength of the ceramic. Moreover, the nanohardness (34.5–36.9 GPa) and Young's modulus (519–571 GPa) values with different B4 C contents just showed a slight difference and were within ranges commonly observed in high-entropy diboride ceramics.