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Showing papers on "Alloy published in 2014"


Journal ArticleDOI
05 Sep 2014-Science
TL;DR: This work examined a five-element high-entropy alloy, CrMnFeCoNi, which forms a single-phase face-centered cubic solid solution, and found it to have exceptional damage tolerance with tensile strengths above 1 GPa and fracture toughness values exceeding 200 MPa·m1/2.
Abstract: High-entropy alloys are equiatomic, multi-element systems that can crystallize as a single phase, despite containing multiple elements with different crystal structures. A rationale for this is that the configurational entropy contribution to the total free energy in alloys with five or more major elements may stabilize the solid-solution state relative to multiphase microstructures. We examined a five-element high-entropy alloy, CrMnFeCoNi, which forms a single-phase face-centered cubic solid solution, and found it to have exceptional damage tolerance with tensile strengths above 1 GPa and fracture toughness values exceeding 200 MPa·m(1/2). Furthermore, its mechanical properties actually improve at cryogenic temperatures; we attribute this to a transition from planar-slip dislocation activity at room temperature to deformation by mechanical nanotwinning with decreasing temperature, which results in continuous steady strain hardening.

3,704 citations


Journal ArticleDOI
TL;DR: A series of six-component (FeCoNiCrMn)100−xAlx (x = 0−20 ǫ) high-entropy alloys was synthesized to investigate the alloying effect of Al on the structure and tensile properties as mentioned in this paper.

954 citations


Journal ArticleDOI
TL;DR: In this article, the authors investigated various binary, ternary and quaternary alloys made from the equiatomic high-entropy alloy FeNiCoCrMn.

659 citations


Journal ArticleDOI
TL;DR: In this article, the evolution of structure with temperature can be classified into four types: Al0−Al0.3, FCC structure; Al0.5−Al 0.7, mixed structure; and spinodal A2+B2 structure.

543 citations


Journal ArticleDOI
TL;DR: In this paper, the microstructure, phase composition and mechanical properties of the AlMo 0.5 NbTa 0.4 Hf 0.6 nbTaTiZr high-entropy alloys are reported.

534 citations


Journal ArticleDOI
TL;DR: In this article, a nonequiatomic FeMnNiCoCr alloy is introduced and characterized at multiple scales employing various characterization techniques (e.g., atom probe tomography, electron channeling contrast imaging, electron backscatter diffraction, etc.) to elucidate the role of configurational entropy and intrinsic tensile ductility of high-entropy alloys.

525 citations


Journal ArticleDOI
TL;DR: In this article, an application of advanced oxidation-resistant iron alloys as light water reactor fuel cladding is proposed, based on specific limitations associated with zirconium alloys.

397 citations


Journal ArticleDOI
TL;DR: In this paper, the evolution of microstructure and texture after heavy cold rolling and subsequent annealing in a wide temperature range was first studied in an equiatomic CoCrFeMnNi high-entropy alloy (HEA).

390 citations


Journal ArticleDOI
26 Aug 2014-Entropy
TL;DR: The alloys were manufactured by conventional and high speed solidification techniques, and their macroscopic, microscopic and nanoscale structures were studied by optical, X-ray and electron microscope methods.
Abstract: This paper describes some underlying principles of multicomponent and high entropy alloys, and gives some examples of these materials. Different types of multicomponent alloy and different methods of accessing multicomponent phase space are discussed. The alloys were manufactured by conventional and high speed solidification techniques, and their macroscopic, microscopic and nanoscale structures were studied by optical, X-ray and electron microscope methods. They exhibit a variety of amorphous, quasicrystalline, dendritic and eutectic structures.

378 citations


Journal ArticleDOI
31 Jul 2014-JOM
TL;DR: In this article, a hexagonal close-packed (hcp) structure was found in YGdTbDyLu and GdTcDdyLu alloys as a nearly single hcp phase.
Abstract: High-entropy alloys (HEAs) with an atomic arrangement of a hexagonal close-packed (hcp) structure were found in YGdTbDyLu and GdTbDyTmLu alloys as a nearly single hcp phase. The equi-atomic alloy design for HEAs assisted by binary phase diagrams started with selecting constituent elements with the hcp structure at room temperature by permitting allotropic transformation at a high temperature. The binary phase diagrams comprising the elements thus selected were carefully examined for the characteristics of miscibility in both liquid and solid phases as well as in both solids due to allotropic transformation. The miscibility in interest was considerably narrow enough to prevent segregation from taking place during casting around the equi-atomic composition. The alloy design eventually gave candidates of quinary equi-atomic alloys comprising heavy lanthanides principally. The XRD analysis revealed that YGdTbDyLu and GdTbDyTmLu alloys thus designed are formed into the hcp structure in a nearly single phase. It was found that these YGdTbDyLu and GdTbDyTmLu HEAs with an hcp structure have delta parameter (δ) values of 1.4 and 1.6, respectively, and mixing enthalpy (ΔH mix) = 0 kJ/mol for both alloys. These alloys were consistently plotted in zone S for disordered HEAs in a δ-ΔH mix diagram reported by Zhang et al. (Adv Eng Mater 10:534, 2008). The value of valence electron concentration of the alloys was evaluated to be 3 as the first report for HEAs with an hcp structure. The finding of HEAs with the hcp structure is significant in that HEAs have been extended to covering all three simple metallic crystalline structures ultimately followed by the body- and face-centered cubic (bcc and fcc) phases and to all four simple solid solutions that contain the glassy phase from high-entropy bulk metallic glasses.

267 citations


Journal ArticleDOI
TL;DR: In this article, the influence of the microstructure and the oxide film of the Mg-9.29Li-0.88Ca alloy on its corrosion behaviour was investigated using SEM, EPMA, XPS and corrosion measurements.

Journal ArticleDOI
TL;DR: In this paper, the performance of binary and quaternary Mg-xCa alloys was investigated using X-ray diffraction, Fourier-transformed infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy dispersive Xray spectroscopic (EDS).

Journal ArticleDOI
TL;DR: In this paper, the tensile strength of steel/Cu SLM parts was evaluated using focused ion beam, scanning electron microscopy, energy dispersive spectroscopy and electron back scattered diffraction techniques.

Journal ArticleDOI
TL;DR: In this paper, the effects of adding nano-alumina particles to Al6061 alloy and extrusion process on the mechanical and microstructure properties of the composites were investigated.

Journal ArticleDOI
TL;DR: In this article, the welding nugget can be considered as aluminum matrix composite, which is enhanced by dispersed sheared-off steel fragments encompassed by a thin inter-metallic layer or simply intermetallic particles.

Journal ArticleDOI
TL;DR: In this paper, the GNFs were mixed with aluminum alloy powders through ball milling and followed by hot isostatic pressing, and the green body was then hot extruded to obtain the final GNFs reinforced aluminum alloy nanocomposite.
Abstract: As one of the most important engineering materials, aluminum alloys have been widely applied in many fields. However, the requirement of enhancing their mechanical properties without sacrificing the ductility is always a challenge in the development of aluminum alloys. Thanks to the excellent physical and mechanical properties, graphene nanoflakes (GNFs) have been applied as promising reinforcing elements in various engineering materials, including polymers and ceramics. However, the investigation of GNFs as reinforcement phase in metals or alloys, especially in aluminum alloys, is still very limited. In this study, the aluminum alloy reinforced by GNFs was successfully prepared via powder metallurgy approach. The GNFs were mixed with aluminum alloy powders through ball milling and followed by hot isostatic pressing. The green body was then hot extruded to obtain the final GNFs reinforced aluminum alloy nanocomposite. The scanning electron microscopy and transmission electron microscope analysis show that GNFs were well dispersed in the aluminum alloy matrix and no chemical reactions were observed at the interfaces between the GNFs and aluminum alloy matrix. The mechanical properties׳ testing results show that with increasing filling content of GNFs, both tensile and yield strengths were remarkably increased without losing the ductility performance. These results not only provided a pathway to achieve the goal of preparing high strength aluminum alloys with excellent ductilitybut they also shed light on the development of other metal alloys reinforced by GNFs.

Journal ArticleDOI
TL;DR: In this article, a super-hydrophobic surface with self-cleaning was successfully deposited on AZ91D magnesium alloy by the nickel plating process, and the surface morphologies, chemical composition, wettability and corrosion resistance were characterized by means of SEM, FT-IR, water contact angle and electrochemical impedance spectroscopy (EIS) measurements.

Journal ArticleDOI
TL;DR: In this paper, an analytical model for the prediction of the dielectric properties of gold-silver alloys is developed, which is a modifi cation of the usual Drude-Lorentz model taking into account the band structure of the metals.
Abstract: An analytical model for the prediction of the dielectric properties of gold– silver alloys is developed. This multi-parametric model is a modifi cation of the usual Drude–Lorentz model that takes into account the band structure of the metals. It is fi tted by a genetic algorithm to the dielectric function of thin alloy fi lms of different gold–silver ratio obtained by ellipsometry. The model is validated for arbitrary alloy compositions by comparing the experimental extinction spectra of alloy nanoparticles with the spectra predicted by Mie theory.

Journal ArticleDOI
TL;DR: Grain refinement through severe plastic deformation enables synthesis of ultrahigh-strength nanostructured materials that impedes dislocation motion and enables an extreme tensile strength of 7 GPa, making this alloy the strongest ductile bulk material known.
Abstract: Grain refinement through severe plastic deformation enables synthesis of ultrahigh-strength nanostructured materials. Two challenges exist in that context: First, deformation-driven grain refinement is limited by dynamic dislocation recovery and crystal coarsening due to capillary driving forces; second, grain boundary sliding and hence softening occur when the grain size approaches several nanometers. Here, both challenges have been overcome by severe drawing of a pearlitic steel wire (pearlite: lamellar structure of alternating iron and iron carbide layers). First, at large strains the carbide phase dissolves via mechanical alloying, rendering the initially two-phase pearlite structure into a carbon-supersaturated iron phase. This carbon-rich iron phase evolves into a columnar nanoscaled subgrain structure which topologically prevents grain boundary sliding. Second, Gibbs segregation of the supersaturated carbon to the iron subgrain boundaries reduces their interface energy, hence reducing the driving force for dynamic recovery and crystal coarsening. Thus, a stable cross-sectional subgrain size $l10\text{ }\text{ }\mathrm{nm}$ is achieved. These two effects lead to a stable columnar nanosized grain structure that impedes dislocation motion and enables an extreme tensile strength of 7 GPa, making this alloy the strongest ductile bulk material known.

Journal ArticleDOI
TL;DR: In this article, the effects of vanadium addition on the microstructure and mechanical properties of AlCoCrFeNiVx (x values in molar ratio, x = 0, 0.5, 0, 1.0) alloys were investigated.

Journal ArticleDOI
TL;DR: In this paper, a detailed study of deformation-induced segregation and precipitation mechanisms in an aluminum alloy containing 5.8% Mg subjected to severe plastic deformation (SPD) is presented.

Journal ArticleDOI
TL;DR: In this paper, the thermal stability studies carried out in the temperature range of 400-600°C for duration of 2-10h in Ar atmosphere suggest that these alloys exhibit excellent thermal stability in terms of phases and crystallite size.

Journal ArticleDOI
TL;DR: In this paper, Selective Laser Melting (SLM) was used to produce 12Si components in three different atmospheres: argon, nitrogen and helium, and the mechanical properties of the components produced in Ar and N2 were superior to those in He, especially the ductility.
Abstract: Al–12Si components were manufactured by Selective Laser Melting (SLM) using three different atmospheres: argon; nitrogen and helium. The atmosphere type did not affect the part's density or hardness and all components reached near full relative density (>97%). The mechanical properties of the components produced in Ar and N2 were superior to those in He, especially the ductility, which has been attributed to the formation of pore clusters in the microstructure. The mechanical properties in SLM-produced components are superior to those produced using conventional method.

Journal ArticleDOI
TL;DR: In this article, the microstructure and mechanical properties of Ti20Zr20Hf20Nb20X20 (X = V or Cr) high-entropy alloys were investigated via X-ray diffractometry and scanning electron microscopy.
Abstract: We investigated the microstructure and mechanical properties of Ti20Zr20Hf20Nb20X20 (X = V or Cr) high-entropy alloys (HEA), produced by induction melting and casting in inert atmosphere. The structures of these alloys were studied via X-ray diffractometry and scanning electron microscopy. Results show that Ti20Zr20Hf20Nb20V20 has mainly the body centered cubic (BCC) structure, whereas the BCC matrix of Ti20Zr20Hf20Nb20Cr20 contains small amount of Cr2Nb and Cr2Hf intermetallic compounds. Ti20Zr20Hf20Nb20V20 alloy shows the high strength and the homogeneous deformation under compression at room temperature. The strength and hardness of Ti20Zr20Hf20Nb20Cr20 alloy are further enhanced by the Cr-containing Laves phases segregated during casting. The structural and mechanical properties remained almost unchanged after a short time (10 min) heat treatment at 573, 773, 973 and 1173 K indicating the resistance to working temperature peaks for these two alloys. Ab initio calculations predict ductile behavior for these and similar refractory HEAs. The theoretically calculated Young's modulus E is in good agreement with the experimental ones.

Journal ArticleDOI
TL;DR: An equiatomic CoCrFeNiAl high-entropy alloy was synthesized by mechanical alloying, and phase evolutions, microstructure, thermal properties and annealing behaviors were investigated as discussed by the authors.

Journal ArticleDOI
TL;DR: In this paper, a systematic study of the relationship between precipitate microstructure and resulting yield strength in an Al-Cu-Li alloy is presented. And the resulting database of micro-structure-strength relationships is used to establish a strengthening model based on interfacial and stacking fault strengthening.

Journal ArticleDOI
24 Jun 2014-JOM
TL;DR: In this paper, the authors present recent developments in the field of austenitic steels with up to 18% reduced mass density, which are based on the Fe-Mn-Al-C system.
Abstract: We present recent developments in the field of austenitic steels with up to 18% reduced mass density. The alloys are based on the Fe-Mn-Al-C system. Here, two steel types are addressed. The first one is a class of low-density twinning-induced plasticity or single phase austenitic TWIP (SIMPLEX) steels with 25–30 wt.% Mn and 10 wt.% Al. Three topics are addressed in more detail, namely, the combinatorial bulk high-throughput design of a wide range of corresponding alloy variants, the development of microstructure–property relations for such steels, and their susceptibility to hydrogen embrittlement.

Journal ArticleDOI
TL;DR: In this article, a nonmetallic carbon element, non-equiatomic Al 0.5 CrFeNiCo 0.3 C 0.2 high entropy alloy has been successfully prepared by mechanical alloying and spark plasma sintering (SPS) process.

Journal ArticleDOI
23 Dec 2014
TL;DR: In this paper, the mechanical properties of different magnesium-rare earth based binary alloys, ternary alloys and other higher alloys with more than three alloying elements are presented.
Abstract: Magnesium-rare earth based alloys are increasingly being investigated due to the formation of highly stable strengthening phases, activation of additional deformation modes and improvement in mechanical properties. Several investigations have been done to study the effect of rare earths when they are alloyed to pure magnesium and other Mg alloys. In this review, the mechanical properties of the previously investigated different magnesium-rare earth based binary alloys, ternary alloys and other higher alloys with more than three alloying elements are presented.