Exploring fracture anisotropy in tantalum carbide compounds: A density functional theory approach

• Published in: Journal of the American Ceramic Society 2024-12, Vol.107 (12), p.7758-7769
• Main Authors: Hossain, Sajjad, Thompson, Gregory B., Weinberger, Christopher R.
• Format: Article
• Language: English
• Subjects: Anisotropy; carbides; Carbon; Cleavage; cleavage planes; Density functional theory; Depletion; fracture; Fractures; Tantalum; Tantalum carbide; Tantalum compounds; zeta phase
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.19917

In this paper, we examine the cleavage fracture anisotropy in tantalum carbides, namely, TaC, α‐Ta2C, and ζ‐Ta4C3 − x, using density functional theory (DFT) calculations. Our investigation identifies the presence of multiple low‐energy cleavage planes indicating multiple potential pathways for crack propagation in these ceramics, even the low symmetry compounds. The anisotropy characteristics of cleavage fractures exhibited by α‐Ta2C and ζ‐Ta4C3 − x closely align with the intrinsic fracture anisotropy observed in TaC. Notably, there exist at least three pyramidal planes in ζ‐Ta4C3 − x whose cleavage energies are less than those of the carbon‐depleted basal planes, previously reported to have the lowest cleavage energy. The observed preference in experiments for cleavage along carbon‐depleted basal planes, exclusive of other identified low‐energy planes, points to factors beyond cleavage energy influencing cleavage plane preference. The anisotropy of cleavage fracture in tantalum carbide compounds was investigated using density functional theory to understand the high fracture toughness of the zeta phase. Surprisingly, these compounds exhibit a large number of low‐energy cleavage planes indicating a tendency for fracture isotropy, suggesting that localized plastic deformation plays a crucial role in determining the preferred paths of cleavage fracture.