Hot Deformation Behavior and Microstructural Characterization of CoCrFeNiNb0.45 Eutectic High Entropy Alloy
11 Jun 2019-Materials Performance and Characterization (ASTM International)-Vol. 8, Iss: 5, pp 1062-1075
TL;DR: In this paper, a high entropy alloy, CoCrFeNiNb0.45, was chosen for a hot deformation study, which consists of a primary face-centered cubic (FCC) phase and a eutectic region between the FCC and Laves phase.
Abstract: In recent years, several multicomponent alloys of near equiatomic composition (also known as high-entropy alloys) with excellent mechanical properties have been developed. In this study, a eutectic high entropy alloy, CoCrFeNiNb0.45, was chosen for a hot deformation study. The alloy consists of a primary face-centered cubic (FCC) phase (CoCrFeNi rich) and a eutectic region between the FCC and Laves phase (Co2Nb type). The combination of FCC and eutectic region is expected to provide better strength and ductility. Hot compression tests were carried out at different strain rates of 0.001, 0.1, 1, and 10 s−1 with varying temperatures of 1,073, 1,173, 1,273, and 1,323 K. The optimum processing window was identified by plotting processing maps, and the instability region was verified using multiple parameters. Constitutive equation relating stress, strain rate, and temperature is established. The optimum processing condition was correlated with the microstructural characterization, and instability was characterized with cracks on the specimen. Finite element simulation was carried out, taking the flow curve as input and correlating the strain field distribution with the microhardness variation. These studies are intended to contribute to an integrated computational materials engineering approach to developing these alloys toward a product.
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References
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TL;DR: A new approach for the design of alloys is presented in this paper, where high-entropy alloys with multi-principal elements were synthesized using well-developed processing technologies.
Abstract: A new approach for the design of alloys is presented in this study. These high-entropy alloys with multi-principal elements were synthesized using well-developed processing technologies. Preliminary results demonstrate examples of the alloys with simple crystal structures, nanostructures, and promising mechanical properties. This approach may be opening a new era in materials science and engineering.
8,175 citations
"Hot Deformation Behavior and Micros..." refers methods in this paper
...The material design domain has expanded from principal element–based approaches to multiprincipal element approaches with the advent of a new alloy design strategy by Yeh et al.1,2 is popularly referred to as high-entropy alloys (HEAs)....
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...The material design domain has expanded from principal element–based approaches to multiprincipal element approaches with the advent of a new alloy design strategy by Yeh et al.(1,2) is popularly referred to as high-entropy alloys (HEAs)....
[...]
TL;DR: High entropy alloys (HEAs) are barely 12 years old as discussed by the authors, and the field has stimulated new ideas and inspired the exploration of the vast composition space offered by multi-principal element alloys.
4,693 citations
15 Aug 1996-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio and excellent corrosion resistance as discussed by the authors.However, titanium usage is strongly limited by its higher cost relative to competing materials, primarily aluminum alloys and steels.
Abstract: Titanium and titanium alloys are excellent candidates for aerospace applications owing to their high strength to weight ratio and excellent corrosion resistance. Titanium usage is, however, strongly limited by its higher cost relative to competing materials, primarily aluminum alloys and steels. Hence the advantages of using titanium must be balanced against this added cost. The titanium alloys used for aerospace applications, some of the characteristics of these alloys, the rationale for utilizing them, and some specific applications of different types of actual usage, and constraints, are discussed as an expansion of previous reviews of β alloy applications. [1,2]
1,938 citations
1,441 citations
TL;DR: A novel strategy to design HEAs using the eutectic alloy concept, i.e. to achieve a microstructure composed of alternating soft fcc and hard bcc phases is proposed, which can be readily adapted to large-scale industrial production of HEAs with simultaneous high fracture strength and high ductility.
Abstract: High-entropy alloys (HEAs) can have either high strength or high ductility, and a simultaneous achievement of both still constitutes a tough challenge. The inferior castability and compositional segregation of HEAs are also obstacles for their technological applications. To tackle these problems, here we proposed a novel strategy to design HEAs using the eutectic alloy concept, i.e. to achieve a microstructure composed of alternating soft fcc and hard bcc phases. As a manifestation of this concept, an AlCoCrFeNi 2.1 (atomic portion) eutectic high-entropy alloy (EHEA) was designed. The as-cast EHEA possessed a fine lamellar fcc/B2 microstructure, and showed an unprecedented combination of high tensile ductility and high fracture strength at room temperature. The excellent mechanical properties could be kept up to 700°C. This new alloy design strategy can be readily adapted to large-scale industrial production of HEAs with simultaneous high fracture strength and high ductility.
938 citations