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Showing papers on "Alloy published in 2019"


Journal ArticleDOI
01 Oct 2019-Nature
TL;DR: Atomic-resolution chemical mapping reveals deformation mechanisms in the CrFeCoNiPd alloy that are promoted by pronounced fluctuations in composition and an increase in stacking-fault energy, leading to higher yield strength without compromising strain hardening and tensile ductility.
Abstract: High-entropy alloys are a class of materials that contain five or more elements in near-equiatomic proportions1,2. Their unconventional compositions and chemical structures hold promise for achieving unprecedented combinations of mechanical properties3–8. Rational design of such alloys hinges on an understanding of the composition–structure–property relationships in a near-infinite compositional space9,10. Here we use atomic-resolution chemical mapping to reveal the element distribution of the widely studied face-centred cubic CrMnFeCoNi Cantor alloy2 and of a new face-centred cubic alloy, CrFeCoNiPd. In the Cantor alloy, the distribution of the five constituent elements is relatively random and uniform. By contrast, in the CrFeCoNiPd alloy, in which the palladium atoms have a markedly different atomic size and electronegativity from the other elements, the homogeneity decreases considerably; all five elements tend to show greater aggregation, with a wavelength of incipient concentration waves11,12 as small as 1 to 3 nanometres. The resulting nanoscale alternating tensile and compressive strain fields lead to considerable resistance to dislocation glide. In situ transmission electron microscopy during straining experiments reveals massive dislocation cross-slip from the early stage of plastic deformation, resulting in strong dislocation interactions between multiple slip systems. These deformation mechanisms in the CrFeCoNiPd alloy, which differ markedly from those in the Cantor alloy and other face-centred cubic high-entropy alloys, are promoted by pronounced fluctuations in composition and an increase in stacking-fault energy, leading to higher yield strength without compromising strain hardening and tensile ductility. Mapping atomic-scale element distributions opens opportunities for understanding chemical structures and thus providing a basis for tuning composition and atomic configurations to obtain outstanding mechanical properties. In high-entropy alloys, atomic-resolution chemical mapping shows that swapping some of the atoms for larger, more electronegative elements results in atomic-scale modulations that produce higher yield strength, excellent strain hardening and ductility.

748 citations


Journal ArticleDOI
TL;DR: In this article, a precipitation-strengthened FeCoNiCrTi0.2 high-entropy alloy strengthened by two types of coherent nano-precipitates but with the same composition was fabricated, and its tensile properties at room and cryogenic temperatures (77 K) and the corresponding defect-structure evolution were investigated.

305 citations


Journal ArticleDOI
TL;DR: In this article, a high strength in-process and post-process friendly Al alloy was developed for the selective laser melting (SLM) process, one of the most commonly used additive manufacturing techniques.

265 citations


Journal ArticleDOI
TL;DR: In this paper, the authors showed that duplex annealing at temperatures below the β transus temperature of the alloy would lead to such a microstructure while retaining the mesostructure, whose nature depends on the process parameter combinations utilized.

188 citations


Journal ArticleDOI
01 Nov 2019-Small
TL;DR: By dealloying predesigned Al-based precursor alloys, it is possible to controllably incorporate Ir with another four metal elements into one single nanostructured phase with merely ≈20 at% Ir, and a record-high OER activity is found for a quinary AlNiCoIrMo np-HEA.
Abstract: Ir-based binary and ternary alloys are effective catalysts for the electrochemical oxygen evolution reaction (OER) in acidic solutions. Nevertheless, decreasing the Ir content to less than 50 at% while maintaining or even enhancing the overall electrocatalytic activity and durability remains a grand challenge. Herein, by dealloying predesigned Al-based precursor alloys, it is possible to controllably incorporate Ir with another four metal elements into one single nanostructured phase with merely ≈20 at% Ir. The obtained nanoporous quinary alloys, i.e., nanoporous high-entropy alloys (np-HEAs) provide infinite possibilities for tuning alloy's electronic properties and maximizing catalytic activities owing to the endless element combinations. Particularly, a record-high OER activity is found for a quinary AlNiCoIrMo np-HEA. Forming HEAs also greatly enhances the structural and catalytic durability regardless of the alloy compositions. With the advantages of low Ir loading and high activity, these np-HEA catalysts are very promising and suitable for activity tailoring/maximization.

187 citations


Journal ArticleDOI
TL;DR: An electron/ion dual-conductive solid framework is proposed by partially dealloying the Li-Mg alloy anode on a garnet-type solid-state electrolyte, creating the possibility to realize high-energy solid- state Li batteries with extended lifespans.
Abstract: The solid-state Li battery is a promising energy-storage system that is both safe and features a high energy density. A main obstacle to its application is the poor interface contact between the solid electrodes and the ceramic electrolyte. Surface treatment methods have been proposed to improve the interface of the ceramic electrolytes, but they are generally limited to low-capacity or short-term cycling. Herein, an electron/ion dual-conductive solid framework is proposed by partially dealloying the Li-Mg alloy anode on a garnet-type solid-state electrolyte. The Li-Mg alloy framework serves as a solid electron/ion dual-conductive Li host during cell cycling, in which the Li metal can cycle as a Li-rich or Li-deficient alloy anode, free from interface deterioration or volume collapse. Thus, the capacity, current density, and cycle life of the solid Li anode are improved. The cycle capability of this solid anode is demonstrated by cycling for 500 h at 1 mA cm-2 , followed by another 500 h at 2 mA cm-2 without short-circuiting, realizing a record high cumulative capacity of 750 mA h cm-2 for garnet-type all-solid-state Li batteries. This alloy framework with electron/ion dual-conductive pathways creates the possibility to realize high-energy solid-state Li batteries with extended lifespans.

185 citations


Journal ArticleDOI
TL;DR: In this article, the properties of 15 single-phase and 11 multi-phase refractory complex concentrated alloys (RCCAs) were investigated using the CALPHAD approach and phase diagrams were calculated to identify the solidus (melting, Tm) temperatures and volume fractions of secondary phases.

179 citations


Journal ArticleDOI
TL;DR: In this article, a relatively dense equiatomic FeCrCoMnNi high entropy alloy with excellent mechanical properties is manufactured by LAM successfully and the effect of heat treatment on phase, microstructure, microhardness, residual stress and mechanical properties of as-built (AB) specimens are investigated.

178 citations


Journal ArticleDOI
TL;DR: In this paper, a detailed atomic-scale mechanism of the dynamic continuous microstructural evolution has been performed, to limit the achievement of bulk dual-phase high-entropy alloys with the improved strength and toughness.

170 citations


Journal ArticleDOI
TL;DR: In this article, the state-of-the-art of the Fe-Si-based soft magnetic materials including their history, structure, properties, processing, and applications are reviewed.

166 citations


Journal ArticleDOI
TL;DR: In this paper, an Al-Zn-Mg-Cu alloy (AA7075) was processed by high pressure torsion (HPT) at room temperature and 200°C, with an objective to reveal the deformation-induced precipitation and segregation of elements at grain boundaries.

Journal ArticleDOI
21 Aug 2019
TL;DR: In this article, a study was conducted using AA6351 aluminum alloy in conjunction with AlN particles whose percentages of incorporation were 4, 8, 12, 16% and 20 wt.% in the ascending order.
Abstract: In the current trend, the hard ceramic particles reinforced aluminum matrix composites (AMCs) is extensively being exploited as a composite which shall be utilized for various engineering applications. In the present research, the Al-Si-Mg (AA6351) composite incorporated with aluminium nitride (AlN) filler were prepared via novel and low cost melt stirring process. This study was conducted using AA6351 aluminum alloy in conjunction with AlN particles whose percentages of incorporation were 4%, 8%, 12%, 16% and 20 wt.% in the ascending. The stir casted composites and the base alloy were characterized via X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX). EDAX and XRD plots prove the occurrence of AlN filler contents in the synthesized AMCs. SEM studies exhibit the even dispersion of the reinforcement particles in the Al matrix. The effects of AlN contents on the mechanical characteristics of AA6351 matrix composites were examined. The dry sliding wear characteristics of the prepared composites was tested employing pin on disc machine. The mechanical and wear behavior of the AMCs had shown a great enhancement by the incorporation of AlN particles into AA6351 matrix alloy. The test outcomes discovered that Al/20 wt.% AlN composites had revealed superior wear resistance, hardness, yield strength and tensile strength than the AA6351 base alloy

Journal ArticleDOI
TL;DR: A low-cost Co-free eutectic high entropy alloy (EHEA) system was designed, successfully prepared and characterized in this article, which showed excellent mechanical properties with an ultimate strength of 1357 MPa and a total elongation of 6.4% at the cast condition.

Journal ArticleDOI
TL;DR: In this article, the mechanism of electrodeposition and effect of operational parameters and deposit microstructure, together with the mechanical, electrochemical and tribological characteristics of Ni Co alloys and included particle, composite deposits.
Abstract: Ni Co alloy electrodeposits have been widely employed in industry due to their good corrosion and wear resistance, high mechanical strength, moderate thermal conductivity and outstanding electrocatalytic and magnetic properties. This review aims to provide an insight into the mechanism of electrodeposition and effect of operational parameters and deposit microstructure, together with the mechanical, electrochemical and tribological characteristics of Ni Co alloys and included particle, composite deposits. Potential applications of the coatings have also been considered in applications as diverse as additive manufacturing, micro-tools, micro-sensors, electronic imaging and electrochemical energy conversion.

Journal ArticleDOI
Wang Lei, Bo Wen, Bai Xiaoyu, Chao Liu, Yang Haibo 
12 Nov 2019
TL;DR: In this article, hierarchical NiCo alloy/carbon nanorod@carbon nanotube (NiCo Alloy/Carbon Nanorod/CNT) structures were prepared by a carbonization process using NiCo-MOF-74 nanorods as precursors in Ar flow, in which the aspect ratio and the coating density of the CNTs were controlled by the ratio of Ni/Co in the precursor.
Abstract: Fabricating high-performance electromagnetic absorbents with strong absorbing intensity and wide effective absorbing bandwidth at low filler loading is still a challenge. Herein, hierarchical NiCo alloy/carbon nanorod@carbon nanotube (NiCo alloy/carbon nanorod@CNT) structures were prepared by a carbonization process using NiCo-MOF-74 nanorods as precursors in Ar flow, in which the aspect ratio of the NiCo alloy/carbon nanorod and the coating density of the CNTs could be easily controlled by the ratio of Ni/Co in the precursor. When the Ni/Co molar ratio was 1:1, a dual electric network was easily formed among the NiCo alloy/carbon nanorods as well as between the intertwined coating CNTs due to the higher aspect ratio and larger coating density, which induced significant enhancement of the comprehensive microwave absorbing properties of the NiCo alloy/carbon nanorod@CNT composites. By adding only 5 wt % to paraffin, the resulting composite displayed a maximum reflection loss of −58.8 dB and a covered an ef...

Journal ArticleDOI
TL;DR: Graphene has been successfully coated with a nano-Al layer through a novel activating treatment (i.e., organic aluminum reduction method) as discussed by the authors, which was further processed into AlSi10Mg alloy based composites through a selective laser melting (SLM) process.

Journal ArticleDOI
TL;DR: In this paper, an effective boronization strategy for the value-added transformation of inexpensive, commercially available metal sheets (Ni, Co, Fe, NiFe alloys and steel sheets) into highly active and stable, corrosion resistant oxygen evolution electrodes was reported.
Abstract: The oxygen evolution reaction (OER) is a key half-reaction involved in many important electrochemical reactions, but this process is quite sluggish and the materials needed usually show unsatisfactory activity, stability or corrosion resistance in the harsh electrocatalysis environment. Here we report an effective boronization strategy for the value-added transformation of inexpensive, commercially available metal sheets (Ni, Co, Fe, NiFe alloys and steel sheets) into highly active and stable, corrosion resistant oxygen evolution electrodes. The boronized metal sheets exhibit OER activities that are an order of magnitude higher than those of the corresponding metal sheets, and show significantly improved catalytic stability and corrosion resistance in the operating environment. The in situ formed, ultrathin (2–5 nm), metaborate-containing oxyhydroxide thin films on metal boride surfaces are identified as a self-functionalized, highly active catalytic phase for the OER. In particular, a boronized NiFe alloy sheet is demonstrated to exhibit intrinsic catalytic activity higher than those of the state-of-the-art materials in 1 M KOH, while retaining such catalytic activity for over 3000 hours. Additionally, the boronized NiFe alloy and steel sheets are also demonstrated to have good catalytic activity as well as excellent catalytic stability and corrosion resistance in 30% KOH solution, a widely-adopted electrolyte in commercial water–alkali electrolyzers.

Journal ArticleDOI
TL;DR: In this article, the influence of temperature and duration of solution and ageing treatment on microstructure, hardness and density of AlSi10Mg alloy produced by direct metal laser sintering was investigated.
Abstract: A solution, quenching and ageing heat treatment is often performed on additive manufactured AlSi10Mg parts to dissolve the anisotropy due to the layer-by-layer building. This study investigates the influence of temperature and duration of solution and ageing treatment on microstructure, hardness and density of AlSi10Mg alloy produced by direct metal laser sintering. A parallel investigation is carried out on AlSi10Mg samples produced by gravity casting to analyse the different response to the same heat treatment conditions. The highest hardness, combined with an acceptable increase of porosity, is reached after selected heat treatment parameters. It was also found that, compared to the as-produced condition, this treatment leads to a decrease of ultimate tensile strength, without affecting the yield strength of additive manufactured samples, and reduces the difference in properties along the two building directions. The high properties of the as-produced samples are related to the finer microstructure and, as proved by the differential scanning calorimetric measurements, to the self-quenching phenomenon.

Journal ArticleDOI
TL;DR: In this paper, high strength aluminum alloy can be fabricated by laser powder bed fusion (LPBF) through alloy design and microstructural control, and the results demonstrate that high strength Al-6Zn-2Mg alloys with 1'wt% (Sc,Zr) additively manufactured by LPBF using gas atomized powders.

Journal ArticleDOI
TL;DR: In this article, the influence of annealing on the microstructure and mechanical properties of SLM-processed AlSi7Mg alloy parts was investigated, and the Vickers hardness and tensile stress greatly reduced, while the elongation increased.
Abstract: Selective laser melting, due to the high energy density input and the small interaction time (106 K/s), can result in an ultrafine microstructure and excellent mechanical properties. However, due to the nonuniform nature of the temperature distribution and the transition from liquid to solid, high residual stresses exist. High residual stresses in the parts can increase the risk of material distortion and cause many problems, such as dimensional inaccuracy or cracks. This work systematically investigated the influence of annealing on the microstructure and mechanical properties of SLM-processed AlSi7Mg alloy parts. The residual stresses relaxed significantly after annealing. The Vickers hardness and the tensile stress greatly reduced, while the elongation increased. The fracture mode of the as-fabricated sample was ductile and brittle mixed fracture, whereas the fracture morphology of the annealed sample presented many more dimples, and the elongation also increased, which indicated the ductile mode.

Journal ArticleDOI
TL;DR: In this article, the microstructure of the AlxCoCrFeNiTiy high entropy alloy (HEA) system was studied using X-ray diffraction, scanning and transmission electron microscopy.

Journal ArticleDOI
Luo Kang1, Liang Zhang1, Guohua Wu1, Wencai Liu1, Wenjiang Ding1 
TL;DR: In this article, the effect of Y content (Mg-xY-1Gd-2Nd-0.5Zn)-on the microstructure and mechanical properties of Mg-Y-RE alloys was investigated.

Journal ArticleDOI
TL;DR: In this paper, the microstructure and mechanical properties of fabricated Inconel625 alloy, and the influence of torch travel speed on the properties of the manufactured specimens were investigated.
Abstract: In the present study Inconel 625 alloy fabricated using Cold Metal Transfer (CMT) Wire Arc Additive Manufacturing (WAAM) has been investigated. The microstructure and mechanical properties of the fabricated Inconel625 alloy, and the influence of torch travel speed on the properties of the manufactured specimens were researched. Microstructural studies revealed variation in microstructure in different layers of the specimen, with the bottom layer consisting of fine primary cellular grains. Mechanical properties that include hardness and tensile properties showed that with the increase in the travel speed, average micro-hardness of the manufactured specimens slightly improved from 248 HV to 253 HV. The ultimate tensile strength (UTS) increased from 647 MPa to 687 MPa, while yield strength (YS) increased from 376 MPa to 400 MPa. Results showed that the mechanical performance of the manufactured components by CMT-WAAM method was better than the mechanical properties of Inconel 625 alloy casting parts except UTS, which demonstrated that the Inconel 625 alloys can be fabricated by cold metal transfer process.

Journal ArticleDOI
TL;DR: In this paper, the tensile yield strength of a single Al0.3CoCrFeNi high entropy alloy (or complex-concentrated alloy), can be enhanced from 160 MPa to over 1800 MPa (1.8 GPa) via microstructural engineering enabled by thermo-mechanical processing of the bulk alloy.

Journal ArticleDOI
TL;DR: In this article, a novel high entropy alloy (HEA) of composition 38Ni-21Cr-20Fe-13Ru-6Mo-2W at.% (33Ni-16Cr-17Fe-19Ru-9Mo-6W wt%) was investigated in sulfate solutions of various pH levels.

Journal ArticleDOI
TL;DR: In this paper, the feasibility of using car scrap aluminium alloy wheels (SAAWs) as the matrix material and spent alumina catalyst (SAC) from oil refineries as reinforcement material was investigated.

Journal ArticleDOI
TL;DR: In this article, the phase composition of high-entropy alloy (HEA) coatings of AlCoCrFeNiTiTix was investigated using X-Ray diffraction.
Abstract: High-entropy alloy (HEA) coatings of AlCoCrFeNiTix (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) were fabricated on AISI1045 steel by laser cladding. X-Ray diffraction (XRD) was used to investigate the phase composition of the coatings. The microstructure of coatings was analyzed using a scanning electron microscopy (SEM) and transmission electron microscopy (TEM). X-Ray diffraction (XRD) was used to investigate the phase composition of the coatings. The potentiodynamic polarization behaviour of coatings and substrate was studied. The composition of passive film on the corroded surface of the coating was identified by X-Ray photoelectron spectroscopy (XPS). The phase composition analysis showed that the coating was mainly composed of disordered body-centered cubic (BCC) solid solution phase (Fe-Cr) and ordered BCC phase (Al-Ni). The microstructure of the coatings was mainly composed of equiaxed polygonal grains, micro-nano particles of TiC and nanoparticles of Al2O3. The spinodal decomposition structure of Fe-Cr enrichment and Al-Ni-Ti enrichment was found in grains. The introduction of Ti led to passivation behavior of the coating during corrosion process. The components of the passive film were Al2O3, TiO2, Ti2O3, Cr2O3 and Cr(OH)3. The AlCoCrFeNiTi HEA coating showed the best corrosion resistance.

Journal ArticleDOI
TL;DR: In this paper, a model was established to estimate the content of each component in the AlCoCrxFeNi high-entropy alloys (HEAs) coatings, based on which three parameters including mixing entropy, net driving factor and atomic size difference were calculated to precisely predict phase constituents in the coatings.

Journal ArticleDOI
TL;DR: A novel chemical energy release induced surface atom diffusion strategy, which is achieved by the negative Gibbs free energy from the surface oxidation reaction and subsequent replacement reaction under thermal treatment in air, to realize a uniform upper ZnO nanoparticles coating is presented.
Abstract: It is imperative to explore practical methods and materials to drive the development of high energy density lithium metal batteries. The constuciton of nanostructure electrodes and surface engineering on the current collectors are the two most effective strategies to regulate the homogeneous Li plating/stripping to relieve the Li dendrites and infinite volume change problems. Based on the low stacking fault energy of the Cu–Zn alloy, we present a novel chemical energy release induced surface atom diffusion strategy, which is achieved by the negative Gibbs free energy from the surface oxidation reaction and subsequent replacement reaction under thermal treatment in air, to realize a uniform upper ZnO nanoparticles coating. Furthermore, we apply the modified brass mesh as a lithiophilic current collector to decrease the Li deposition nucleation overpotential and effectively restrain the Li dendrite growth. The modified brass current collector achieves a long-term cycling stability of 500 cycles at 2.0 mA cm...

Journal ArticleDOI
TL;DR: In this article, the effect of temperature on the tribological properties of Al0.6CoCrFeNi high-entropy alloy was studied and the results showed that the σ-CrFe phase was precipitated after heat treatment.