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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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Affiliation(s)
- P R Howie
- Department of Materials Science and Metallurgy, 27 Charles Babbage Rd, Cambridge, CB3 0FS, UK
| | - R P Thompson
- Department of Materials Science and Metallurgy, 27 Charles Babbage Rd, Cambridge, CB3 0FS, UK
| | - S Korte-Kerzel
- Institut für Metallkunde und Metallphysik, RWTH Aachen University, Kopernikusstraße 14, 52074, Aachen, Germany
| | - W J Clegg
- Department of Materials Science and Metallurgy, 27 Charles Babbage Rd, Cambridge, CB3 0FS, UK.
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Sandlöbes S, Friák M, Korte-Kerzel S, Pei Z, Neugebauer J, Raabe D. A rare-earth free magnesium alloy with improved intrinsic ductility. Sci Rep 2017; 7:10458. [PMID: 28874798 PMCID: PMC5585333 DOI: 10.1038/s41598-017-10384-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2017] [Accepted: 08/09/2017] [Indexed: 11/09/2022] Open
Abstract
Metals are the backbone of manufacturing owing to their strength and formability. Compared to polymers they have high mass density. There is, however, one exception: magnesium. It has a density of only 1.7 g/cm3, making it the lightest structural material, 4.5 times lighter than steels, 1.7 times lighter than aluminum, and even slightly lighter than carbon fibers. Yet, the widespread use of magnesium is hampered by its intrinsic brittleness. While other metallic alloys have multiple dislocation slip systems, enabling their well-known ductility, the hexagonal lattice of magnesium offers insufficient modes of deformation, rendering it intrinsically brittle. We have developed a quantum-mechanically derived treasure map which screens solid solution combinations with electronic bonding, structure and volume descriptors for similarity to the ductile magnesium-rare earth alloys. Using this insight we synthesized a surprisingly simple, compositionally lean, low-cost and industry-compatible new alloy which is over 4 times more ductile and 40% stronger than pure magnesium. The alloy contains 1 wt.% aluminum and 0.1 wt.% calcium, two inexpensive elements which are compatible with downstream recycling constraints.
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Affiliation(s)
- S Sandlöbes
- Institut für Metallkunde und Metallphysik, Kopernikusstr. 14, RWTH Aachen University, 52074, Aachen, Germany. .,Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straβe 1, 40237, Düsseldorf, Germany.
| | - M Friák
- Institute of Physics of Materials, Academy of Sciences of the Czech Republic, v.v.i., Žižkova 22, Brno, 616 62, Czech Republic.,Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straβe 1, 40237, Düsseldorf, Germany
| | - S Korte-Kerzel
- Institut für Metallkunde und Metallphysik, Kopernikusstr. 14, RWTH Aachen University, 52074, Aachen, Germany.
| | - Z Pei
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straβe 1, 40237, Düsseldorf, Germany
| | - J Neugebauer
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straβe 1, 40237, Düsseldorf, Germany
| | - D Raabe
- Max-Planck-Institut für Eisenforschung GmbH, Max-Planck-Straβe 1, 40237, Düsseldorf, Germany.
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