High-Entropy Alloys

High-Entropy Alloys

The goal of our group is to develop novel high-entropy alloys (HEAs) with exceptional mechanical, physical and chemical properties based on the understanding of their structure-properties relations. This is being achieved by using the advanced experimental techniques and the state-of-the-art theoretical methods.

Figure 1: Strength-ductility profiles of various classes of metallic materials including our recently developed HEAs.

Conventional alloy design over the past centuries has been constrained by the concept of one or two prevalent base elements. As a breakthrough of this restriction, the concept of HEAs opens a new realm of numerous opportunities for investigations in the huge unexplored compositional space of multi-component alloys.

As a typical example shown in Figure 1, while conventional alloys use strengthening mechanisms such as grain boundaries, dual-phase structure, dislocation interactions, precipitates and solid solution (e.g. steels, Ti-alloys, Al-alloys), our recently developed novel interstitial TWIP-TRIP-HEAs concept combines all available strengthening effects, namely, interstitial and substitutional solid solution, TWIP, TRIP, multiple phases, precipitates, dislocations, stacking faults and grain boundaries. This leads to the exceptional strength-ductility combination of the novel HEAs, exceeding that of most metallic materials.

Our research group (High-Entropy Alloys) conducts the state-of-the-art research work employing novel experimental-theoretical methodologies (e.g., EBSD, ECCI, FIB-APT, TEM, Calphad and DFT; Figure 2) in the following specific aspects:

  • Excellent strength-ductility combination of transitional metal HEAs;
  • Resistances to hydrogen-embrittlement and corrosion of HEAs
  • Light-weight high-strength HEAs
  • High-temperature refractory high-strength HEAs
  • Multifunction of HEAs
  • Defects, segregations and thermodynamics in HEAs
  • In-situ observation of deformations in HEAs under electron microscopes

These aspects are strongly interconnected and facilitate an extensive collaboration network with national and international experts.

Figure 2: Representative microstructural information obtained from an interstitial TWIP-TRIP-HEA sample by combining multiple advanced characterization techniques. ECCI: Electron channeling contrast imaging; EBSD: Electron backscatter diffraction; TEM: Transmission electron microscopy; APT: Atom probe tomography; TWIP: Twinning-induced plasticity; TRIP: Transformation-induced plasticity.

Key Publications

Zhiming Li, Alfred Ludwig, Alan Savan, Hauke Springer, and Dierk Raabe, "Combinatorial metallurgical synthesis and processing of high-entropy alloys," Journal of Materials Research 33 (19), 3156-3169 (2018).
Wenjun Lu, Christian Liebscher, Gerhard Dehm, Dierk Raabe, and Zhiming Li, "Bidirectional Transformation Enables Hierarchical Nanolaminate Dual‐Phase High‐Entropy Alloys," Advanced Materials 30 (44), 1804727 (2018).
Zhiming Li, Fritz Körmann, Blazej Grabowski, Jörg Neugebauer, and Dierk Raabe, "Ab initio assisted design of quinary dual-phase high-entropy alloys with transformation-induced plasticity," Acta Materialia 136, 262-270 (2017).
Zhiming Li, Cemal Cem Tasan, Hauke Springer, Baptiste Gault, and Dierk Raabe, "Interstitial atoms enable joint twinning and transformation induced plasticity in strong and ductile high-entropy alloys," Scientific Reports 7, 40704 (2017).
Zhiming Li, Cemal Cem Tasan, Konda Gokuldoss Pradeep, and Dierk Raabe, "A TRIP-assisted dual-phase high-entropy alloy: Grain size and phase fraction effects on deformation behavior," Acta Materialia 131, 323-335 (2017).
Hong Luo, Zhiming Li, and Dierk Raabe, "Hydrogen enhances strength and ductility of an equiatomic high-entropy alloy," Scientific Reports 7 (1), 9892 (2017).
Zhiming Li and Dierk Raabe, "Strong and Ductile Non-equiatomic High-Entropy Alloys: Design, Processing, Microstructure, and Mechanical Properties," JOM-Journal of the Minerals Metals & Materials Society 69 (11), 2099-2106 (2017).
Zhiming Li, Konda Gokuldoss Pradeep, Yun Deng, Dierk Raabe, and Cemal Cem Tasan, "Metastable high-entropy dual-phase alloys overcome the strength–ductility trade-off," Nature 534, 227-230 (2016).
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