Preparation of FeCoNi medium entropy alloy from Fe^(3+)-Co^(2+)-Ni^(2+)solution system

In recent years,medium entropy alloys have become a research hotspot due to their excellent physical and chemical performances.By controlling reasonable elemental composition and processing parameters,the medium entropy alloys can exhibit similar properties to high entropy alloys and have lower costs.In this paper,a FeCoNi medium entropy alloy precursor was prepared via sol-gel and coprecipitation methods,respectively,and FeCoNi medium entropy alloys were prepared by carbothermal and hydrogen reduction.The phases and magnetic properties of FeCoNi medium entropy alloy were investigated.Results showed that FeCoNi medium entropy alloy was produced by carbothermal and hydrogen reduction at 1500℃.Some carbon was detected in the FeCoNi medium entropy alloy prepared by carbothermal reduction.The alloy prepared by hydrogen reduction was uniform and showed a relatively high purity.Moreover,the hydrogen reduction product exhibited better saturation magnetization and lower coercivity.

Influence of introducing Zr,Ti,Nb and Ce elements on externally solidified crystals and mechanical properties of high-pressure die-casting Al–Si alloy

High pressure die casting(HPDC)AlSi10Mn Mg alloy castings are widely used in the automobile industry.Mg can optimize the mechanical properties of castings through heat treatment,while the release of thermal stress arouses the deformation of large integrated die-castings.Herein,the development of non-heat treatment Al alloys is becoming the hot topic.In addition,HPDC contains externally solidified crystals(ESCs),which are detrimental to the mechanical properties of castings.To achieve high strength and toughness of non-heat treatment die-casting Al-Si alloy,we used AlSi9Mn alloy as matrix with the introduction of Zr,Ti,Nb,and Ce.Their influences on ESCs and mechanical properties were systematically investigated through three-dimensional reconstruction and thermodynamic simulation.Our results reveal that the addition of Ti increased ESCs'size and porosity,while the introduction of Nb refined ESCs and decreased porosity.Meanwhile,large-sized Al_3(Zr,Ti)phases formed and degraded the mechanical properties.Subsequent introduction of Ce resulted in the poisoning effect and reduced mechanical properties.

Effects of the extrusion parameters on microstructure,texture and room temperature mechanical properties of extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy

Microstructure,texture,and mechanical properties of the extruded Mg-2.49Nd-1.82Gd-0.2Zn-0.2Zr alloy were investigated at different extrusion temperatures(260 and 320℃),extrusion ratios(10:1,15:1,and 30:1),and extrusion speeds(3 and 6 mm/s).The experimental results exhibited that the grain sizes after extrusion were much finer than that of the homogenized alloy,and the second phase showed streamline distribution along the extrusion direction(ED).With extrusion temperature increased from 260 to 320℃,the microstructure,texture,and mechanical properties of alloys changed slightly.The dynamic recrystallization(DRX)degree and grain sizes enhanced as the extrusion ratio increased from 10:1 to 30:1,and the strength gradually decreased but elongation(EL)increased.With the extrusion speed increased from 3 to 6 mm/s,the grain sizes and DRX degree increased significantly,and the samples presented the typical<2111>-<1123>rare-earth(RE)textures.The alloy extruded at 260℃ with extrusion ratio of 10:1 and extrusion speed of 3 mm/s showed the tensile yield strength(TYS)of 213 MPa and EL of 30.6%.After quantitatively analyzing the contribution of strengthening mechanisms,it was found that the grain boundary strengthening and dislocation strengthening played major roles among strengthening contributions.These results provide some guidelines for enlarging the industrial application of extruded Mg-RE alloy.

Study on the hydrogen absorption properties of a YGdTbDyHo rare-earth high-entropy alloy

This study investigated the microstructure and hydrogen absorption properties of a rare-earth high-entropy alloy(HEA),YGdTbDyHo.Results indicated that the YGdTbDyHo alloy had a microstructure of equiaxed grains,with the alloy elements distributed homogeneously.Upon hydrogen absorption,the phase structure of the HEA changed from a solid solution with an hexagonal-close-packed(HCP)structure to a high-entropy hydride with an faced-centered-cubic(FCC)structure without any secondary phase precipitated.The alloy demonstrated a maximum hydrogen storage capacity of 2.33 H/M(hydrogen atom/metal atom)at 723 K,with an enthalpy change(ΔH)of-141.09 kJ·mol^(-1)and an entropy change(ΔS)of-119.14 J·mol^(-1)·K^(-1).The kinetic mechanism of hydrogen absorption was hydride nucleation and growth,with an apparent activation energy(E_(a))of 20.90 kJ·mol^(-1).Without any activation,the YGdTbDyHo alloy could absorb hydrogen quickly(180 s at 923 K)with nearly no incubation period observed.The reason for the obtained value of 2.33 H/M was that the hydrogen atoms occupied both tetrahedral and octahedral interstices.These results demonstrate the potential application of HEAs as a high-capacity hydrogen storage material with a large H/M ratio,which can be used in the deuterium storage field.

Addressing the strength-ductility trade-off in a cast Al-Li-Cu alloy—Synergistic effect of Sc-alloying and optimized artificial ageing scheme

A dramatic improvement of strength and ductility of cast Al-2.5Li-1.5Cu-1Zn-0.5Mg-0.15 Zr alloy was obtained by the collaboration of Sc-alloying and optimized ageing scheme.Joint and independent influence of Sc-alloying and different ageing temperatures were investigated.The results revealed that a substantial increase was realized in the hardness of Sc-containing alloy,and the ageing response time was only influenced by ageing temperature.Coarse and heterogeneousδ'(Al_(3)Li),wideδ'-precipitation free zones(δ'-PFZs),and a large amount of T_(1)(Al_(2)CuLi)precipitates were observed in Sc-containing alloy aged at 175℃,which resulted in superior yield strength and poor elongation.The Sc-containing alloy obtained an excellent combination of ductility(elongation=8.2%)and tensile strength(ultimate strength=565 MPa)suffered to 150℃ ageing for 64 h.The increase in the elongation was mainly due to the combined effect of grain refining,much finerδ',and extremely narrowδ'-PFZs(<10 nm),while the higher strength was mainly attributed to the formation of Al_(3)(Sc,Zr,Li)composite particles and a large amount of S'(Al_(2)CuMg)phase.However,the enhancement of the different ageing temperature(150℃ and 175℃)on the mechanical properties of the alloys without Sc addition was not obvious.

MATERIAL CONSTANTS OF AN Al-Li-Cu-Mg-Zr ALLOY DURING DEFORMATION AT ELEVATED TEMPERATURES

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A PAT STUDY OF INFLUENCES OF PRECIPITATION ON DEFECTS AND ELECTRONIC DENSITY IN Al-Li-Cu-Mg-Zr ALLOYS

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Effects of solution treatment on mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy

Mechanical properties and microstructures of Al-Li-Cu-Mg-Ag alloy after solution treatments were investigated by means of optical microscopy （OM）, tensile test, hardness measurement and electrical conductivity test, differential scanning calorimetric （DSC）, energy dispersive X-ray （EDX）, scanning electron microscopy （SEM） and transition electron microscopy （TEM）, respectively The results show that both tensile strength and hardness increase first and then decrease with temperature at constant holding time of 30 min with maximum strength and hardness appearing at 520 ℃. Tensile strength, hardness and elongation of samples treated at 520 ℃ for 30 min are 566 MPa （σb）, 512 MPa （σ0.2）, HB 148 and 8.23% （δ）, respectively. There are certain amount of fine T1 （AI2CuLi） phase dispersing among AI substrates according to TEM images. This may result in mixed fracture morphology with trans-granular and inter-granular delamination cracks observed in SEM images.

Low-temperature fusion fabrication of Li-Cu alloy anode with in situ formed 3D framework of inert LiCu_x nanowires for excellent Li storage performance

The commercialization of rechargeable Li metal batteries is hindered by dendrite growth and volumetric variation. Herein, we report a Li-rich dual-phase Li-Cu alloy with built-in 3 D conductive skeleton to replace conventional planar Li anode. The Li-Cu alloy is simply prepared by fusion of Li and Cu metals at a relatively low-temperature of 500 °C, followed by a cooling process where phase-segregation leads to metallic Li phase distributed in the network of LiCu_x solid solution phase. Different from the common Li alloy, the electrochemical alloying reaction between Li and Cu metals is not observed. Therefore, the lithiophilic LiCu_x nanowires guides conformal plating of Li and the porous framework provides superior dimensional stability for the anode. This unique ferroconcrete-like structure of Li-Cu alloy enables dendrite-free Li plating for an expanded cycling lifetime. Constructing a new type of Li alloy with in situ formed electrochemically inactive framework is a promising and easily scaled-up strategy toward practical application of Li metal anodes.

Identifying the crystal structure of T 1 precipitates in Al-Li-Cu alloys by ab initio calculations and HAADF-STEM imaging

Controversial experimental reports on the crystal structure of T 1 precipitates in Al-Li-Cu alloys have ex-isted for a long time,and all of them can be classified into five models.To clarify its ground-state atomic structure,herein,we have combined high-throughput first-principles calculations and CALPHAD,as well as aberration-corrected HAADF-STEM experiments.Employing the special quasi-random structure(SQS)and supercell approximation(SPA)methods to simulate the local disorder on Al-Cu sub-lattices,we find that none of the present models can satisfy the phase stability in Al-Li-Cu ternary system based on temperature-dependent convex hull analysis.Using the cluster expansion(CE)formulas,structural predic-tions derived from the five-frame models were performed.Subsequently,by introducing the vibrational contribution to the free energy at aging temperatures,we proposed a novel ground-state T 1 structure that maintains a coherent relationship with Al-matrix at the<112>Al orientation.The underlying phase transition between the variants of T 1 precipitates was further discussed.By means of ab initio molecular dynamics(AIMD)simulations,we resolved the controversy regarding the number of atomic layers con-stituting the T 1 phase and acknowledged the existence of Al-Li corrugated layers.The root cause of this structural distortion is triggered by atomic forces and bondings.Our work can have an positive impact on the novel fourth generation of Al-Cu-Li alloy designs by engineering the T 1 strengthening phase.

Interactions between cadmium and multiple precipitates in an Al-Li-Cu alloy:Improving aging kinetics and precipitation hardening

This work demonstrates significant improvements in both the aging kinetics and precipitation hardening of an Al-Li-Cu alloy with the minor addition of Cd(0.06 at.%).The precipitation hardening effect of T1 precipitates in casting Al-Li-Cu alloys has long been ignored since it is difficult to achieve a high number density of fine precipitates without a large number of dislocations.A detailed transmission electron microscopy investigation shows that the Cd addition has changed the distribution of T1 precipitates from the conventional uneven distribution near dislocations or grain boundaries to a more homogeneous manner.Most of the Cd-rich nanoparticles were observed at the broad face and/or terminal of the T1 platelets.It is highly likely that these nanoparticles act as heterogeneous nucleation sites,which consequently leads to a higher number density of T1 precipitates.Moreover,Cd atoms were preferentially segregated withinδprecipitates,which can be attributed to the strong bonding between Li and Cd.The interactions between Cd and the T1(Al2CuLi)andδ′(Al3Li)precipitates in Al-Li-Cu alloy are first reported.The present study may propose a new mechanism to effectively improve precipitation kinetics and therefore the age-hardening effect of Al-Li-Cu alloys.

Accelerated design of high-performance Mg-Mn-based magnesium alloys based on novel bayesian optimization

Magnesium(Mg),being the lightest structural metal,holds immense potential for widespread applications in various fields.The development of high-performance and cost-effective Mg alloys is crucial to further advancing their commercial utilization.With the rapid advancement of machine learning(ML)technology in recent years,the“data-driven''approach for alloy design has provided new perspectives and opportunities for enhancing the performance of Mg alloys.This paper introduces a novel regression-based Bayesian optimization active learning model(RBOALM)for the development of high-performance Mg-Mn-based wrought alloys.RBOALM employs active learning to automatically explore optimal alloy compositions and process parameters within predefined ranges,facilitating the discovery of superior alloy combinations.This model further integrates pre-established regression models as surrogate functions in Bayesian optimization,significantly enhancing the precision of the design process.Leveraging RBOALM,several new high-performance alloys have been successfully designed and prepared.Notably,after mechanical property testing of the designed alloys,the Mg-2.1Zn-2.0Mn-0.5Sn-0.1Ca alloy demonstrates exceptional mechanical properties,including an ultimate tensile strength of 406 MPa,a yield strength of 287 MPa,and a 23%fracture elongation.Furthermore,the Mg-2.7Mn-0.5Al-0.1Ca alloy exhibits an ultimate tensile strength of 211 MPa,coupled with a remarkable 41%fracture elongation.

Relationship between the unique microstructures and behaviors of high-entropy alloys

High-entropy alloys(HEAs),which were introduced as a pioneering concept in 2004,have captured the keen interest of nu-merous researchers.Entropy,in this context,can be perceived as representing disorder and randomness.By contrast,elemental composi-tions within alloy systems occupy specific structural sites in space,a concept referred to as structure.In accordance with Shannon entropy,structure is analogous to information.Generally,the arrangement of atoms within a material,termed its structure,plays a pivotal role in dictating its properties.In addition to expanding the array of options for alloy composites,HEAs afford ample opportunities for diverse structural designs.The profound influence of distinct structural features on the exceptional behaviors of alloys is underscored by numer-ous examples.These features include remarkably high fracture strength with excellent ductility,antiballistic capability,exceptional radi-ation resistance,and corrosion resistance.In this paper,we delve into various unique material structures and properties while elucidating the intricate relationship between structure and performance.

Influence of Metalloid Elements on the Magnetic Properties and Anisotropy of FeNi-based Amorphous Alloys

The magnetic properties and anisotropy of amor- phous(Fe_(80)Ni_(20))_(78)Si_xB_(22-x).alloys have been investigated systematically.The maximum permeability,coercive force and remanence have been determined for as-prepared and annealed samples,The results on the technical magnetic properties of this alloy system have been discussed and compared with Masumoto's.

MICROSTRUCTURE AND MECHANICAL BEHAVIOUR OF Al-Li-Zr AND Al-Li-Cu-Mg-Zr ALLOYS

The aging response,tensile and impact properties of two kinds of Al-Li based alloys have been studied.The microstructure,deformation as well as fracture behaviour in the alloys were observed with SEM and TEM.It was found that the mechanisms of deformation and fracture for different heat-treated alloys with the same chemical composition are quite different.The causes leading to the drop of ductility,toughness as well as anisotropy in peak-aged alloys have been analysed.Finally,possible methods to improve the ductility and toughness of the al- loys have been discussed.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF AN Al-Li-Cu-Mg-Zr ALLOY CONTAINING MINOR LANTHANUM ADDITIONS

The effect of the addition of minor amounts of La on the microstructure and mechanicalproperties of an Al-Li-Cu-Mg-Zr alloy was studied.The results showed that in Al-Li alloyssome impurities,such as Fe,Si and Na segregated on the grain boundaries,and the addition ofminor amounts of La decreased the segregation of these impurities.In addition,La could giverise to grain refinement,and retard the growth of precipitates.The tensile properties andtoughness of the Al-Li alloy containing minor amounts of La were improved compared with theLa-free Al-Li alloy.

EFFECT OF TENSION CONDITIONS ON SUPERPLASTIC BEHAVIOUR OF AN Al-Li-Cu-Mg-Zr ALLOY

A much higher elongation of a warm rolled superplastic Al-Li-Cu-Mg-Zr alloy was made under two-stage strain rate tests comparing with the single ones.During initial stage of deformation a deformation-induced continuous recrystallization which converted a subgrain structure into a recrystallized grain structure by a continuous increase in boundary misorientations had occurred.The higher the strain rate,the faster the continuous recrystallization and the finer the recrystallized grains.The fine recrystallized grain structure formed during the first stage deformation is the essential condition for the material to have high strain rate hardening and strain hardening during the low second stage superplastic deformation.The combination of strain rate hardening and strain hardening is the reason why the higher elongation may be obtained during two-stage superplastic deformation of the alloy.

BEHAVIOUR AND MECHANISM OF STRESS CORROSION CRACKING FOR Al-Li-Cu-Mg ALLOY

Studies were made of the influence of aging conditions and applied potentials on the stress corrosion carcking(SCC)susceptibility for an Al-Li-Cu-Mg alloy by slow strain rate technique.The relationship between the relative hydrogen content on specimen surface,the applied potentials and elapsed time has also been examined.The SCC susceptibility was found to be dependent on aging conditions in which the peak aged condition gave the worst SCC resistance and the natural aged condition had the best one. The SCC susceptibility and surface hydrogen content relates to the applied potentials. The anodic potentials increase SCC susceptibility,while the cathodic ones below the critical potential accelerate SCC.It is considered that both the anodic dissolution and

Microstructure and damping properties of LPSO phase dominant Mg-Ni-Y and Mg-Zn-Ni-Y alloys

This work studied the microstructure,mechanical properties and damping properties of Mg_(95.34)Ni_(2)Y_(2.66) and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys systematically.The difference in the evolution of the long-period stacked ordered(LPSO)phase in the two alloys during heat treatment was the focus.The morphology of the as-cast Mg_(95.34)Ni_(2)Y_(2.66)presented a disordered network.After heat treatment at 773 K for 2 hours,the eutectic phase was integrated into the matrix,and the LPSO phase maintained the 18R structure.As Zn partially replaced Ni,the crystal grains became rounded in the cast alloy,and lamellar LPSO phases and more solid solution atoms were contained in the matrix after heat treatment of the Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloy.Both Zn and the heat treatment had a significant effect on damping.Obvious dislocation internal friction peaks and grain boundary internal friction peaks were found after temperature-dependent damping of the Mg_(95.34)Ni_(2)Y_(2.66)and Mg_(95.34)Zn_(1)Ni_(1)Y_(2.66)alloys.After heat treatment,the dislocation peak was significantly increased,especially in the alloy Mg_(95.34)Ni_(2)Y_(2).66.The annealed Mg_(95.34)Ni_(2)Y_(2.66)alloy with a rod-shaped LPSO phase exhibited a good damping performance of 0.14 atε=10^(−3),which was due to the difference between the second phase and solid solution atom content.These factors also affected the dynamic modulus of the alloy.The results of this study will help in further development of high-damping magnesium alloys.

High corrosion and wear resistant electroless Ni–P gradient coatings on aviation aluminum alloy parts

A Ni–P alloy gradient coating consisting of multiple electroless Ni–P layers with various phosphorus contents was prepared on the aviation aluminum alloy. Several characterization and electrochemical techniques were used to characterize the different Ni–P coatings’ morphologies, phase structures, elemental compositions, and corrosion protection. The gradient coating showed good adhesion and high corrosion and wear resistance, enabling the application of aluminum alloy in harsh environments. The results showed that the double zinc immersion was vital in obtaining excellent adhesion (81.2 N). The optimal coating was not peeled and shredded even after bending tests with angles higher than 90°and was not corroded visually after 500 h of neutral salt spray test at 35℃. The high corrosion resistance was attributed to the misaligning of these micro defects in the three different nickel alloy layers and the amorphous structure of the high P content in the outer layer. These findings guide the exploration of functional gradient coatings that meet the high application requirement of aluminum alloy parts in complicated and harsh aviation environments.