Abstract
Metals have been mankind’s most essential materials for thousands of years; however, their use is affected by ecological and economical concerns. Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength–ductility trade-off1,2. Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases. High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization3,4,5,6. Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection7,8,9,10,11, the concept is overturned. We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase12); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase13). This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels14,15 and massive solid-solution strengthening of high-entropy alloys3. In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength. Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility. This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials16,17. This metastability-engineering strategy should thus usefully guide design in the near-infinite compositional space of high-entropy alloys.
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References
Ritchie, R. O. The conflicts between strength and toughness. Nature Mater. 10, 817–822 (2011)
Wei, Y. et al. Evading the strength–ductility trade-off dilemma in steel through gradient hierarchical nanotwins. Nature Commun. 5, 3580 (2014)
Yeh, J. W. et al. Nanostructured high-entropy alloys with multiple principal elements: novel alloy design concepts and outcomes. Adv. Eng. Mater. 6, 299–303 (2004)
Zhang, Y. et al. Microstructures and properties of high-entropy alloys. Prog. Mater. Sci. 61, 1–93 (2014)
Gludovatz, B. et al. Exceptional damage-tolerance of a medium-entropy alloy CrCoNi at cryogenic temperatures. Nature Commun. 7, 10602 (2016)
Gludovatz, B. et al. A fracture-resistant high-entropy alloy for cryogenic applications. Science 345, 1153–1158 (2014)
Yao, M. J., Pradeep, K. G., Tasan, C. C. & Raabe, D. A novel, single phase, non-equiatomic FeMnNiCoCr high-entropy alloy with exceptional phase stability and tensile ductility. Scr. Mater. 72–73, 5–8 (2014)
Tasan, C. C. et al. Composition dependence of phase stability, deformation mechanisms, and mechanical properties of the CoCrFeMnNi high-entropy alloy system. JOM 66, 1993–2001 (2014)
Pradeep, K. G. et al. Non-equiatomic high entropy alloys: approach towards rapid alloy screening and property-oriented design. Mater. Sci. Eng. A 648, 183–192 (2015)
Deng, Y. et al. Design of a twinning-induced plasticity high entropy alloy. Acta Mater. 94, 124–133 (2015)
Wang, Y. P., Li, B. S. & Fu, H. Z. Solid solution or intermetallics in a high-entropy alloy. Adv. Eng. Mater. 11, 641–644 (2009)
Tasan, C. C. et al. An overview of dual-phase steels: advances in microstructure-oriented processing and micromechanically guided design. Annu. Rev. Mater. Res. 45, 391–431 (2015)
Herrera, C., Ponge, D. & Raabe, D. Design of a novel Mn-based 1 GPa duplex stainless TRIP steel with 60% ductility by a reduction of austenite stability. Acta Mater. 59, 4653–4664 (2011)
Hadfield, R. A. Hadfield’s manganese steel. Science 12, 284–286 (1888)
Grässel, O., Krüger, L., Frommeyer, G. & Meyer, L. W. High strength Fe–Mn–(Al, Si) TRIP/TWIP steels development–properties–application. Int. J. Plast. 16, 1391–1409 (2000)
Wu, X. et al. Heterogeneous lamella structure unites ultrafine-grain strength with coarse-grain ductility. Proc. Natl Acad. Sci. USA 112, 14501–14505 (2015)
Kim, S.-H., Kim, H. & Kim, N. J. Brittle intermetallic compound makes ultrastrong low-density steel with large ductility. Nature 518, 77–79 (2015)
Pierce, D. T. et al. The influence of manganese content on the stacking fault and austenite/ε-martensite interfacial energies in Fe–Mn–(Al–Si) steels investigated by experiment and theory. Acta Mater. 68, 238–253 (2014)
Mandal, S., Pradeep, K. G., Zaefferer, S. & Raabe, D. A novel approach to measure grain boundary segregation in bulk polycrystalline materials in dependence of the boundaries’ five rotational degrees of freedom. Scr. Mater. 81, 16–19 (2014)
Dmitrieva, O. et al. Chemical gradients across phase boundaries between martensite and austenite in steel studied by atom probe tomography and simulation. Acta Mater. 59, 364–374 (2011)
Raabe, D. et al. Segregation engineering enables nanoscale martensite to austenite phase transformation at grain boundaries: a pathway to ductile martensite. Acta Mater. 61, 6132–6152 (2013)
Otto, F. et al. The influences of temperature and microstructure on the tensile properties of a CoCrFeMnNi high-entropy alloy. Acta Mater. 61, 5743–5755 (2013)
Hays, C., Kim, C. & Johnson, W. L. Microstructure controlled shear band pattern formation and enhanced plasticity of bulk metallic glasses containing in situ formed ductile phase dendrite dispersions. Phys. Rev. Lett. 84, 2901 (2000)
Hofmann, D. C. et al. Designing metallic glass matrix composites with high toughness and tensile ductility. Nature 451, 1085–1089 (2008)
Zaefferer, S. & Elhami, N.-N. Theory and application of electron channelling contrast imaging under controlled diffraction conditions. Acta Mater. 75, 20–50 (2014)
Yakubtsov, I. A., Ariapour, A. & Perovic, D. D. Effect of nitrogen on stacking fault energy of f.c.c. iron-based alloys. Acta Mater. 47, 1271–1279 (1999)
Brooks, J. W., Loretto, M. H. & Smallman, R. E. Direct observations of martensite nuclei in stainless steel. Acta Metall. 27, 1839–1847 (1979)
Kim, C. P., Oh, Y. S., Lee, S. & Kim, N. J. Realization of high tensile ductility in a bulk metallic glass composite by the utilization of deformation-induced martensitic transformation. Scr. Mater. 65, 304–307 (2011)
Lu, K., Lu, L. & Suresh, S. Strengthening materials by engineering coherent internal boundaries at the nanoscale. Science 324, 349–352 (2009)
Wang, M. M., Tasan, C. C., Ponge, D., Dippel, A. C. & Raabe, D. Nanolaminate transformation-induced plasticity–twinning-induced plasticity steel with dynamic strain partitioning and enhanced damage resistance. Acta Mater. 85, 216–228 (2015)
Acknowledgements
This work is financially supported by the European Research Council under the EU’s 7th Framework Programme (FP7/2007-2013)/ERC grant agreement 290998. The contributions of H. Springer, S. Zaefferer, M. Nellessen, M. Adamek and F. Schlüter are also gratefully acknowledged.
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C.C.T. and D.R. designed the research; Z.L. was the lead experimental scientist of the study; K.G.P. and Y.D. performed some of the alloy design experiments; and Z.L. and C.C.T. wrote the paper. All authors discussed the results and commented on the manuscript.
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Extended data figures and tables
Extended Data Figure 1 Statistical binomial frequency distribution analysis results for the APT tip.
The statistical analysis shows that the tip has an overall composition of Fe48.6Mn27.6Co11.3Cr12.3 (at%). The binomial curves obtained from the experiments match the curves corresponding to a total random distribution. The quality of the fit was quantified using several parameters, as listed in the key. nd is the number of degrees of freedom for a given ion. The values of the normalized homogenization parameter μ for all four elements are close to 0, confirming the random distribution of elements in the DP-HEA.
Extended Data Figure 2 Strain distribution within the DP-HEA sample upon room-temperature deformation.
a, Evolution of local strain with increasing the global strain (εglo.), indicating an extended uniform deformation process. The red dotted circles in a indicate the local strain values corresponding to various positions in the fractured tensile sample shown in b; four positions with local strains of 10%, 30%, 45% and 65% were highlighted by percentages in red and the corresponding microstructures are shown in Fig. 4. b, Digital image correlation strain map shows the local strain distribution of the tensile sample following fracture. 0 to 11 in b refers to the distance of the sample position from the fracture surface, corresponding to the distance values shown in a.
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Li, Z., Pradeep, K., Deng, Y. et al. Metastable high-entropy dual-phase alloys overcome the strength–ductility trade-off. Nature 534, 227–230 (2016). https://doi.org/10.1038/nature17981
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DOI: https://doi.org/10.1038/nature17981
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