The direct selective laser sintering (SLS) process was successfully demonstrated for additive manufacturing of high-entropy carbide ceramics (HECC), in which a Yb fiber laser was employed for ultrafast (in seconds) reactive sintering of HECC specimens from a powder mixture of constitute monocarbides. A single-phase non-equiatomic HECC was successfully formed in the 4-HECC specimen with a uniform distribution of Zr, Nb, Hf, Ta, and C. In contrast, a three-layer microstructure was formed in the 5-HECC specimen with five metal elements (Zr, Nb, Hf, Ta and Ti), consisting of a TiC-rich top layer, a Zr–Hf–C enriched intermediate layer, and a non-equiatomic Zr–Ta–Nb–Hf–C HECC layer. Vickers hardness of 4- and 5-HECC specimens were 22.2 and 21.8 GPa, respectively, on the surface. These findings have important implications on the fundamental mechanisms governing interactions between laser and monocarbide powders to form a solid solution of HECCs during SLS.
(Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C high‐entropy ceramics (HEC) with a submicron grain size of 400 to 600 nm were fabricated by spark plasma sintering using a two‐step sintering process. Both X‐ray and neutron diffractions confirmed the formation of single‐phase with rock salt structure in the as‐fabricated (Hf0.2Zr0.2Ta0.2Nb0.2Ti0.2)C samples. The effect of submicron grain size on the thermal stability and mechanical properties of HEC was investigated. The grain growth kinetics in the fine‐grained HEC was small at 1300 and 1600°C, suggesting high thermal stability that was possibly related to the compositional complexity and sluggish diffusion in HEC. Compared to the coarse‐grain HEC with a grain size of 16.5 µm, the bending strength and fracture toughness of fine‐grained HEC were 25% and 20% higher respectively. The improvement of mechanical properties in fine‐grained HEC may be attributed to micromechanistic mechanisms such as crack deflection.
more » « less- NSF-PAR ID:
- 10457093
- Publisher / Repository:
- Wiley-Blackwell
- Date Published:
- Journal Name:
- Journal of the American Ceramic Society
- Volume:
- 103
- Issue:
- 8
- ISSN:
- 0002-7820
- Page Range / eLocation ID:
- p. 4463-4472
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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