Howie PR, Thompson RP, Korte-Kerzel S, Clegg WJ. Softening non-metallic crystals by inhomogeneous elasticity.
Sci Rep 2017;
7:11602. [PMID:
28912469 PMCID:
PMC5599516 DOI:
10.1038/s41598-017-09453-1]
[Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 07/26/2017] [Indexed: 11/18/2022] Open
Abstract
High temperature structural materials must be resistant to cracking and oxidation. However, most oxidation resistant materials are brittle and a significant reduction in their yield stress is required if they are to be resistant to cracking. It is shown, using density functional theory, that if a crystal’s unit cell elastically deforms in an inhomogeneous manner, the yield stress is greatly reduced, consistent with observations in layered compounds, such as Ti3SiC2, Nb2Co7, W2B5, Ta2C and Ta4C3. The mechanism by which elastic inhomogeneity reduces the yield stress is explained and the effect demonstrated in a complex metallic alloy, even though the electronegativity differences within the unit cell are less than in the layered compounds. Substantial changes appear possible, suggesting this is a first step in developing a simple way of controlling plastic flow in non-metallic crystals, enabling materials with a greater oxidation resistance and hence a higher temperature capability to be used.
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