Search

The wetting characteristics of Ti 32.8 Zr 30.2 Fe x Cu 14.3- x Be 22.7 (at.%, x = 0, 2.5, 5.3) bulk metallic glasses (BMGs) with W substrate are conducted using the sessile drop method at different temperatures. The effect of Fe content on wettability is systematically studied. At a given temperature, contact angle initially rises and subsequently declines as the Fe content increases from 0 at.% to 5.3 at.%. Optimal wettability is observed in BMGs devoid of the Fe element. This is attributed to the influence of Fe addition on the elemental diffusion behaviors and two-phase interfacial morphologies during wetting. The addition of 2.5 at.% Fe leads to a significant accumulation of Ti element at the wetting interface and prevents the wetting process. As the Fe content increases to 5.3 at.%, the conspicuous abundance of Fe in the glass phase together with the diffused Cu in W substrate determines the wettability of the system. These findings not only reveal the influence of Fe content on the wetting properties of the TiZr-based BMGs/W system but also provide a theoretical basis for the preparation of ex-situ BMG composites. • The contact angle first increases and then decreases with increasing Fe content. • Optimal wettability is observed in BMGs devoid of the Fe element. • Fe content has a significantly influence on the interface morphology of wetting. • Diffusion behavior of atomic clusters directly determines interfacial wettability. [ABSTRACT FROM AUTHOR]

Focusing on the manufacturing challenges associated with the formation of high-strength Aluminum-lithium (Al-Li) alloys, this study explores the laser powder bed fusion (LPBF) additive manufacturing method. The influence of hatch spacing on the characteristics of 2195 Al-Li alloy fabricated by LPBF is investigated. The findings suggest that variations in hatch spacing affect the overlap between "layer-to-layer" and "channel-to-channel", resulting in a maximum relative density of 99.06% and microhardness of 130.0 HV, respectively. The grain morphology exhibits epitaxial growth of columnar grains along the maximum temperature gradient. The crystalline phases, such as T 2 (Al 6 CuLi 3) and θ′/Ω (Al 2 Cu), are widely dispersed within the α-Al matrix, where the formation of Mg-Ag atomic clusters promotes the nucleation of the Ω phase. The 2195 specimen exhibits an ultimate tensile strength (UTS) of 295.03 ± 5.77 MPa and an elongation of 5.01 ± 0.13%. The hatch spacing significantly affects the forming quality, while metallurgical defects, fine grain strengthening, dislocation strengthening, and secondary phase strengthening collectively determine the mechanical properties of the 2195 Al-Li alloy. • The variation of hatch spacing affects the overlap between melt pools, leading to the formation of pores. • The increase in hatch spacing can significantly refine the grain size, and increase the dislocation density. • The primary crystalline phases in the 2195 Al-Li alloy consist of the T 2 phase and the θ′/Ω phase. • Optimizing the hatch spacing can increase the tensile strength and toughness of the 2195 Al-Li alloy. [ABSTRACT FROM AUTHOR]

Chemical short-range order (CSRO) is a typical microstructural characteristic commonly found in multi-principal element alloys (MPEAs). For MPEAs with the face-centered cubic (FCC) structure, the presence of CSRO has been verified and characterized meticulously by using electron microscope. However, it is still challenging to reveal the effect of CSRO structure on the deformation microstructure and micromechanical behavior of those alloys. By applying atomic scale simulations, this study explores the micromechanical behavior of an equiatomic CoCrNi medium entropy alloy with random solid solution and three different degrees of CSRO under plane strain compression, respectively. The results show that CSRO can effectively promote planar slip of dislocations in the FCC matrix and elevate flow stress of the alloy. The planar slip and stacking of partial dislocations then lead to the formation of hexagonal-close-packed (HCP) structure lamellae. CSRO also modulates the morphology of dislocations. When dislocations cut through CSRO, it hinders the movement of dislocations while being destroyed by atomic plastic flow, causing CSRO and atomic clusters at the interface of the matrix to embed each other and generate antiphase boundaries which can significantly enhance the bulk yield strength. These findings provide fundamental insights into the interaction between CSRO and dislocations in CoCrNi MEA, guiding the design of MPEAs with superior combinations of strength and ductility. [Display omitted] • Interaction between chemical short-range order (CSRO) and dislocations in the CoCrNi MEA is unraveled. • Deformation mechanisms depend on the degree of CSRO. • Plastic deformation deteriorates CSRO. The more significant the CSRO, the easier it is to be destroyed with deformation. [ABSTRACT FROM AUTHOR]

Gd-based metallic microfibers have been the research highlights due to the significant magnetocaloric effect. Herein, the atomic cluster micro-regions are constructed in Gd-based microfibers to further improve the magnetocaloric effect. The results show that the continuous and amorphous microfibers with excellent softly magnetic and thermal stability properties are obtained. The maximum magnetic entropy change -Δ S m max of Gd-based microfibers increases first and then decreases with Ni alloying degree increase. Among which, the better magnetocaloric properties is obtained in (Gd 60 A 20 lCo 20) 95 Ni 5 microfibers. The maximum magnetic entropy change, refrigeration capacity (RC), and relative cooling power (RCP) at 5 T reach 11.57 J/kg K, 834.14 J/kg, and 1138.16 J/kg, respectively. The outstanding magnetocaloric properties of microfibers are attributed to the indirect interaction coupling caused by Ni elements and the atomic cluster micro-regions, which lead to a fundamental shift in magnetic entropy. The findings of this study promote the application of Gd-based microfibers in the field of magnetic refrigeration. • The excellent magnetocaloric properties are obtained in GdAlCoNi5 microfibers after Ni alloyed. • The -Δ S m max, RC and RCP of GdAlCoNi5 microfibers reach 11.57 J/kg·K, 834.14 J/kg and 1138.16 J/kg, respectively. • The atomic cluster micro-regions promote the transformation of magnetic entropy disorder to order after Ni alloyed. [ABSTRACT FROM AUTHOR]

Developing robust and durable nonprecious metal ORR electrocatalysts for use in both alkaline and acidic media is still challenging. Herein, highly dispersed Mn atomic clusters and standalone Fe nanoparticles dual-sites in-situ confined nitrogen doped carbon nanotubes (Mn-Fe@NCNTs) were fabricated via a facile one-step process of high-temperature calcination and simultaneous chemical vapor deposition. The resultant Mn-Fe@NCNTs catalysts exhibited excellent ORR catalytic activity and durability in both alkaline and acidic media due to the special constitute and structure, which not only provided abundant active sites and defects, good electronic conductivity and effective electron transfer, but also enhanced the corrosion resistance and decreased the Fenton reactivity of the catalyst. In 0.1 M KOH solution, the half-wave potential of Mn-Fe@NCNTs is 0.872 V, more positive than that of the commercial Pt/C catalyst (E 1/2 = 0.835 V) and many other previously reported NCNTs based non-precious metal ORR electrocatalysts. While in 0.1 M HClO 4 solution, Mn-Fe@NCNTs exhibits a half-wave potential of 0.760 V, only 60 mV negative shift compared to the Pt/C catalyst. Furthermore, the as-prepared catalysts exhibit much higher stability, with much lower current attenuation and smaller shift of the ORR polarization curves after continuous chronoamperometric testing for 29,000 s and continuous CV test for 5,000 cycles, than those of Pt/C in both alkaline and acidic solutions. When applied in Zn-air batteries for testing, the Mn-Fe@NCNTs electrocatalysts are obviously outperforming the commercial Pt/C with higher specific capacity of 774.0 mAh g−1 Zn and power density of 139.2 mW cm−2. This study offers a facile and instructive protocol for developing low-cost and high-efficiency electrocatalysts to be applied in fuel cells, metal-air cells and many other clean electrochemical storage devices. [Display omitted] • Mn atomic clusters and Fe nanoparticles dual-sites in-situ confined NCNTs were fabricated via a facile one-step process. • Mn atomic clusters devoted rich active sites and effectively regulated electronic structure and *OH adsorption. • In-situ confinement of Mn atomic clusters in NCNTs decreased the Fenton reactivity and improved the stability of Mn-Fe@NCNTs. • Mn-Fe@NCNTs exhibited excellent ORR catalytic activity and stability in both alkaline and acidic media. • The maximum power density of the Mn-Fe@NCNTs based ZAB is 139.2 mW cm−2, outperforming the Pt/C based ZAB (106 mW cm−2). [ABSTRACT FROM AUTHOR]

The age-hardening response during two-step aging in Al-Mg-Si alloys depends on the nanoclusters formed at the early stage of phase decomposition. However, understanding of the evolution and thermal stability of the nanoclusters is still lacking. This paper discusses clustering behavior during natural aging (NA) and pre-aging (PA) at 50 ℃ through various experiments [hardness, differential scanning calorimetry (DSC), electrical resistivity and three-dimensional atom probe (3DAP)]. A rapid increase in hardness is confirmed due to the acceleration of cluster formation during PA, and a larger area of an endothermic peak is confirmed during DSC thermal analysis compared to NA specimens. Hardness and electrical resistivity were clearly decreased in the PA specimens at the initial stage of two-step aging since the formation of thermally unstable clusters, the Mg-enriched clusters identified by 3DAP, was accelerated during PA. A long aging time at 50 ℃ produces Mg-enriched clusters rather than facilitating the transition from Cluster (1) to Cluster (2). To investigate the atomic arrangement of a cluster, we conducted further analysis for chemical composition of clusters through the normalization for the different sizes of cluster. We found that the Mg-rich clusters with the core-shell structure where Mg atoms are segregated around the cluster-matrix interface, cause thermally unstable at the initial stage of two-step aging. The direct experimental evidence primarily proves that atomic arrangement inside a cluster is a more critical factor than its size for the thermal stability of a cluster in Al-Mg-Si alloys. • Clustering evolution during aging at room temperature and 50 ℃ through various approach was discussed. • The Mg-rich clusters with the core-shell structure cause thermally unstable at the initial stage of two-step aging. • The thermal stability of a cluster is determined by atomic arrangement inside a cluster rather than its size. [ABSTRACT FROM AUTHOR]

The evolution of structural characteristics and mechanical properties of Cu-Zr metallic glasses during multiple recovery annealing process was investigated via molecular dynamics simulation. Firstly, the aged and rejuvenated samples were prepared after the first recovery annealing by varying the annealing temperature. Then, these samples were subsequently treated with the following annealing process. It is found that when reheating the firstly aged sample (annealing at 900 K) to a higher annealing temperatures of 1100 K at the second annealing, the degree of rejuvenation was even higher than that of the initially rejuvenated sample (annealing at 1100 K) at the same temperature. Microstructural analysis shows that the degree of rejuvenation shows a strong correlation with Cu-centered clusters, around a 4% difference in < 0, 0, 12, 0 > (high local fivefold symmetry) content between the most aged and most rejuvenated samples. Moreover, the volume variation of different atomic clusters in the rejuvenated samples is more obvious. It is noted that the initial aged samples can be rejuvenated to an even higher degree when compared with initial rejuvenated ones. The more icosahedral clusters in the aged sample contributes to such phenomenon since they are more easily modified to other types with low local fivefold symmetry at high annealing temperature during the second annealing. The present study demonstrates that the appropriate multiple recovery annealing can rejuvenate the sample to a higher degree. • Multiple recovery annealing can adjust the degree of ageing or rejuvenation. • Firstly aged sample can rejuvenate to a higher degree after multiple annealing. • More icosahedral structures with high local atomic symmetry in firstly aged sample. • The icosahedral clusters are more easily to be modified when annealed again. [ABSTRACT FROM AUTHOR]

The possibility to design new superatom species by decorating Zintl polyanions with alkali metal cations has been examined under density functional theory in this work. Utilizing typical Zintl ions as examples, MLi n +1 + cations have been constructed and investigated in detail. Calculations show that all of the Zintl anions M n − preserve their geometric and electronic integrity in the global minima of MLi n +1 + cations. The stability of these studied cations is guaranteed by the strong ionic bonds between the Zintl core and ligands, as well as their large HOMO−LUMO gaps and positive dissociation energies with respect to the loss of a Li + cation. In particular, all these proposed cations possess pretty low vertical electron affinities, verifying their superalkali or pseudoalkali identities. Besides, the feasibility of using these proposed MLi n +1 + cations as building blocks to design new superatom compounds is explored by theoretically constructing and charactering two series of MLi n +1 −(super)halogen compounds. We, therefore, hope that this work will not only provide an approach to obtain new superatoms by utilizing various Zintl polyanions as the central cores, but also offer new building blocks for cluster-assembled nanomaterials in which exceptionally strong reducing matters are required. [ABSTRACT FROM AUTHOR]

In this paper lattice dynamics of dodecaborides RB 12 (R = Zr, Yb, Lu) is studied using the superatom model. Within this model, a group of strongly bound boron atoms placed at the vertices of cubooctahedron is substituted with a superatom, which possesses the mass equal to the sum of the masses of all atoms in the cluster. Based on this approach, phenomenological models for Yb(Lu)B 12 and ZrB 12 describing phonon dispersion up to 45 meV for Yb(Lu)B 12 and up to 35 meV for ZrB 12 are developed. Good agreement between experimental and modeled dispersion curves is found in both acoustic and low-energy optic regions for ZrB 12 , while in Yb(Lu)B 12 , description of acoustic phonons can only be regarded as satisfactory. The comparison with Einstein oscillator approximation is presented. Analysis of the interatomic interactions is performed on the basis of the Born von Karman force constants model. It is shown that the model makes it possible to calculate specific heat with a 5% error margin up to approximately 100 K, while a more commonly used Debye model only provides correct values up to 60 K. [ABSTRACT FROM AUTHOR]

Needle-shaped precipitates and atomic clusters were evaluated in two model Al-Mg-Si alloys with different Mg/Si ratios by transmission electron microscopy (TEM) and atom probe tomography (APT). Following a solution heat treatment with rapid quenching, specimens were naturally aged for about 3 month and then artificially aged for various times at 170 °C. In the peak-aged condition (aged for 86.4 ks) the Si-rich alloy (6M9S) produced a higher fraction of perfect β" phase with a narrower size distribution than the Mg-rich alloy (8M7S). This resulted in a Mg-depleted matrix in the 6M9S alloy. Clusters with a mean radius of about 1 nm were observed in-between the needle precipitates in both alloys. Their number density was clearly higher in the 8M7S alloy than in the 6M9S alloy in the peak-aged condition. The number fraction of Mg-rich clusters is increasing in the Mg-rich alloy with prolonged aging time, indicating a higher stability of these clusters. Finally, the mechanical properties of the two alloys were predicted using precipitate and cluster statistics measured by APT and TEM. These simulations indicate that clusters present in-between the needle precipitates contribute significantly to strength. [ABSTRACT FROM AUTHOR]

In the present study, the effect of C micro-alloying on microstructure evolution and properties of metastable immiscible Cu-20Fe alloy was comprehensively investigated. Experimental results indicate that the microstructure of Cu-Fe alloy is extremely sensitive to the C content. It was found that obvious liquid-liquid phase separation (LLPS) behavior is observed in Cu-20Fe alloy after C micro-alloying, and the tendency of LLPS is enhanced with increasing C content. The calculation of ΔScc(0) suggests that C atoms preferentially pair with free Fe atoms to form new Fe (C) atomic clusters, thus resulting in the enhancement of bonding of the like-atom pairs. In addition, the quasi-binary phase diagram calculation further reveals the existence of a stable miscibility gap for C-containing alloys, and the temperature interval of miscibility gap is significantly enlarged with increasing C content. Meanwhile, the interface energy between two liquids formed by LLPS also slightly increases as C content increasing. These above reasons should be responsible for the microstructure evolution of Cu-20Fe-xC alloys. In addition, the C micro-alloying deteriorates the soft magnetic properties of Cu-Fe alloys to a certain extent, whereas improves its corresponding wear-resistance. • The microstructure evolution and solidification behavior of Cu-20Fe-xC alloys were clearly elucidated. • The calculation of ΔScc(0) indicates that C atoms preferentially pair with free Fe atoms to form new Fe(C) atomic cluster. • Phase calculation indicates that the metastable miscibility gap of Cu-20Fe alloy is stabilized by the introduction of C. • The addition of appropriate amount C enhances the wear-resistance of Cu-20Fe alloy. [ABSTRACT FROM AUTHOR]

The β ′ precipitate phases formed in Mg–Y alloys, which exhibit characteristic periodic arrays of Y-rich zigzag-shaped atomic clusters at regular intervals of 1.1 nm, have attracted significant attention owing to their precipitation-hardening effect on the matrix. To investigate the formation mechanism of such cluster arrays, the interaction energies between Y clusters at various distances were quantitatively evaluated using first-principles calculations based on density functional theory. We found a weak but distinct interaction between the clusters caused by the interplay between attractive chemical interactions and repulsive relaxation energies. This interplay determines the energetically favorable structure of the cluster arrangements, and these structures are consistent with the experimental observations. We suggest that the long-range intercluster interactions dominate the alignment of Y clusters, which leads to the formation of β ′ precipitates in the Mg matrix, followed by the short-range clustering of Y atoms. [ABSTRACT FROM AUTHOR]

A new method was proposed to pinpoint the compositions with good glass forming ability (GFA) by combining atomic clusters and mixing entropy. The clusters were confirmed by analyzing competing crystalline phases. The method was applied to the Zr–Al–Ni–Cu–Ag alloy system. A series of glass formers with diameter up to 20 mm were quickly detected in this system. The good glass formers were located only after trying 5 compositions around the calculated composition. The method was also effective in other multi-component systems. This method might provide a new way to understand glass formation and to quickly pinpoint compositions with high GFA. [ABSTRACT FROM AUTHOR]

We report the results of the study of equilibrium structures, magnetic properties and stability of small free Co x Sn y clusters with x + y ⩽ 5 within the framework of density functional theory as implemented in SIESTA code. We find that optimized structures of these binary clusters prefer geometries with high coordinations and show significant variations as compared to that of the pure clusters; all the clusters show magnetic behavior independently of the Co concentration; the excess energy reveals a favorable mixing of the constituent atoms. [ABSTRACT FROM AUTHOR]

• Rich and uncovered active sites of FeN x atom clusters were obtained. • The 3D precursor is converted into 2D nanosheets to expose more active sites. • Improved ORR activity is due to the largely exposed FeN x atom clusters. [Display omitted] It is still challenging but essential to synthesize non-noble catalysts with rich and uncovered catalytic active sites towards oxygen reduction reaction (ORR). And the limited research of the ORR properties of FeN x atom clusters also hinders their practical implementations. Here, we report a two-dimensional (2D) non-precious ORR catalyst constructed by abundant and fully exposed FeN x atom clusters anchored on nitrogen-doped graphene nanosheets (Fe-N-C/NG), which derives from three-dimensional (3D) ZIF-8, 2D graphene oxide nanosheet, and ferrocene. The optimized Fe-N-C/NG delivers outstanding ORR activities (E onset = 0.97 V, E 1/2 = 0.84 V, J d = 5.48 mA cm−2), excellent Tafel slope (57.7 mV dec−1), remarkable long-term durability, and strong methanol tolerance in an alkaline electrolyte. Its superior catalytic activity is possibly attributed to its unique conversion of nanoarchitecture and the synergistic effects: the change of morphology effectively utilizes the advantages of 2D graphene oxide and 3D ZIF-8, which guarantees sufficient and reachable active sites; the 2D porous nanoarchitecture of Fe-N-C/NG promotes the ion diffusion and mechanical stability; both the FeN x atom clusters and N-doped graphene nanosheets facilitate the catalytic activity. This work introduces an innovative strategy to rationally design the nanoarchitecture and facilely synthesize nonprecious ORR catalysts with sufficient and uncovered active sites for high efficiency and durability. [ABSTRACT FROM AUTHOR]

The effects of Bi modification and ultrasonic treatment (UST) on the microstructure and mechanical properties of AlMg5Si2Mn alloy were investigated. Compared to the alloy without any treatment, the eutectic Mg 2 Si phases are refined effectively by Bi addition, and its morphology is changed from the mazelike thick lamellars for the base alloy to thin coralline fibers for the containing Bi alloy. The modification of eutectic Mg 2 Si phase is attributed to the Bi segregation and composition supercooling in front of the growing Mg 2 Si phase. UST can assist modification of Bi on the eutectic Mg 2 Si phase and change the morphology of the primary α-Al phase in the AlMg5Si2Mn alloy from coarse dendrites to small near-spherical equiaxed crystals, meanwhile, which can also promote the homogenization of the treated melt and uniform distribution of Bi atoms or clusters in the melt. Moreover, the yield strength, ultimate tensile strength and elongation of the alloy modified by 0.3% Bi addition combined with UST at 660 °C are obviously enhanced, and the fracture modes of the alloys are changed from brittleness to toughness. • For the first time we combine the effect of bismuth modification and ultrasonic treatment to investigate the microstructure evolution and tensile properties of as-cast AlMg5Si2Mn alloy. • Both the Mg 2 Si and α-Al phases were significantly modified and refined simultaneously. • The tensile properties were significantly enhanced by changing fracture mode from brittleness to ductility. [ABSTRACT FROM AUTHOR]

● Short range order in CrMnFeCoNi high-entropy alloy surveyed from the resistivity. ● Electric pulse current (electropulsing) applied to reveal hidden properties. ● No large resistivity changes indicated absence of unstable local atom clusters. ● Slight resistivity changes suggested Cr-Ni pair formation tendency in CrMnFeCoNi. High-entropy alloys (HEAs) are equimolar solid solution alloys composed of more than five elements, and their atomic arrangement is chemically disordered. Some ordering in HEAs, however, is suspected from the characteristic properties, such as high strength with good ductility at low temperatures or sluggish diffusion. Herein, we report that quasi-stable states inherent in nonequilibrium systems can be extracted by applying an electric pulse current to the system (electropulsing). In this study, changes in the electrical resistivity of the rapid-quenched CrMnFeCoNi HEA were investigated after electropulsing. No step-like large decreases reflecting nanocrystallization in amorphous alloys were observed for rapid-quenched CrMnFeCoNi by electropulsing. This indicates that quasi-stable ordered atom clusters do not exist in the CrMnFeCoNi HEA. However, the resistivity showed a slight decrease and increased with increasing electropulsing current density. A tendency to form short-range order, as Cr is preferentially surrounded by Ni, is suggested by comparison with the results of NiCr alloys. [ABSTRACT FROM AUTHOR]

• In addition can suppress the negative effect of NA and improve precipitation during AA for Al-Mg-Si alloys. • In atoms incorporate into clusters and facilitate their transformation to β′′ phase at the early AA. • In atoms segregate at the β′′/α-Al and β′/α-Al interfaces by replacing the Si atoms or Al atoms. • In-rich particles are formed at the edge of the β′ phase or in the α-Al matrix. [Display omitted] The impact of In addition on the precipitation behavior and properties for Al-Mg-Si alloys under different aging treatments was systematically studied by hardness measurements, atom probe tomography (APT), high angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and density functional theory (DFT) calculations. We found that the In addition effectively suppresses the harmful effect of natural aging (NA), and improves the age hardening for the Al-Mg-Si alloy. Mg-Si-In clusters are formed in the early stage of aging caused by the incorporation of In atoms, which can facilitate the nucleation of the β" phase. During peak aging, In atoms distort the well-ordered structure of the β" and occupy the positions in the interface of the β", facilitating the transition of β" to post-β" (i.e., U2 and β′). During the following aging, In atoms are presented in two different configurations: forming In-rich particles and aggregation at the interfaces of β′. Most of the In-rich particles are formed at the edge of the β′ particles. The segregation of In atoms at the precipitate/matrix interface and the formation of In-rich particles can probably be attributed to the reduced strain energy of the β′ phase it brings about. [ABSTRACT FROM AUTHOR]

• Essential mechanisms of deformation in annealed fully amorphous alloys was studied. • Higher annealing temperature leads to higher yield strength and poor plasticity. • The deformation behavior is tuned by free volumes, clusters and atomic packing. • Structural changes influence formation of shear transition zones and shear bands. [Display omitted] An insightful investigation on the deformation behavior of annealed metallic glass (MG) has been conducted in this study to uncover the essential mechanisms of deformation in annealed MGs that remain fully amorphous, a subject that is complex and challenging to the MG scientific community. By coupling synchrotron radiation-based experiments with a series of molecular dynamics simulations and calculations, representative microstructure models of deformed MGs in as-prepared and annealed conditions were successfully probed. It was discovered that higher maximum strength and poor plasticity of the annealed MGs are manifestations of the causative effect of higher temperatures from the annealing treatment. The deformation behavior was tuned by microstructural parameters, in terms of fraction of free volumes (FFVs), clusters and atomic packing efficiencies (APEs) to classify the evolution phenomena. The observed variations of APE and FFV values underscored the distinctions in the deformation behavior of the MG models. However, annealing-induced structural changes significantly influenced the initiation and propagation of shear transition zones, formation of shear bands and the overall deformation behavior with a beneficial strengthening effect. In totality, this work has provided compelling results to demystify the intricacies associated with the microstructural tuning of deformation behavior in annealed MGs. [ABSTRACT FROM AUTHOR]

• High Mg-content AlSiMg1.4 alloy was fabricated by selective laser melting. • YS and UTS of SLMed AlSiMg1.4 alloy reached 341 ± 14 MPa and 518 ± 6 MPa, respectively. • The strength of alloy are much higher than most known SLM fabricated Al-Si-Mg alloys. • The new strengthening mechanism was mentioned in the paper. A high Mg-content AlSiMg1.4 alloy was designed for selective laser melting (SLM) processing. The SLMed AlSiMg1.4 alloy exhibits a high yield strength of 341±14 MPa and a high ultimate tensile strength of 518±6 MPa, along with a total elongation of 7.1±0.4%. The composition profile in the α -Al matrix of the alloy manifests in-phase concentration fluctuations of Mg and Si. The presence of high density Mg-Si atomic clusters as strong obstacles to dislocation gliding is suggested to provide an additional strengthening mechanism for the SLMed Al-Si-Mg alloy. [ABSTRACT FROM AUTHOR]

• Simultaneously enhanced hardness and electrical conductivity in a Cu–Ni–Si alloy by addition of Cobalt. • The precipitation evolution of Cu–Ni–Si and Cu–Ni–Co–Si aged at 500 for different time are investigated in detail. • The existence of spinodal decomposition has been confirmed in the Cu–Ni–Si alloy, while is not found in the Cu–Ni–Co–Si alloy. • The formation process of Ni 2 Si and (Ni, Co) 2 Si phases during aging process are characterized at the atomic scale using 3DAP. The effects of Co on the physical properties and precipitation evolution of a Cu–Ni–Si alloy are investigated via hardness and electrical conductivity testing, transmission electron microscopy and a quantitative three-dimensional atom probe. The precipitation sequence of Cu–Ni–Si alloy aging at 500 °C can be expressed as supersaturated solid solution → solute clusters → GP zones → Ni 2 Si phases. In the early aging stage, the formation of atomic clusters is accompanied by the occurrence of spinodal decomposition. The addition of Co accelerates the redistribution and agglomeration of solute atoms, resulting in the nucleation of (Ni, Co) 2 Si phases directly from the supersaturated state, which further hinders atomic cluster formation and spinodal decomposition. The Ni 2 Si and (Ni, Co) 2 Si phases, which are divided into a region II containing pure Ni 2 Si and the (Ni, Co) 2 Si phase and an unstable region I containing a small amount of Cu atoms, show the same crystal structure and orientation relationship with the matrix. During the aging process, the range of region I is gradually replaced by the core stable region II and accompanied by the growth of the total thickness of the precipitated phase. This remarkable age effect with Co addition can be attributed to the enhanced number of (Ni, Co) 2 Si precipitates, which simultaneously increases the strength and electrical conductivity. [ABSTRACT FROM AUTHOR]

The effects of trace Fe-doping on the magnetic and magnetocaloric performances of Gd-based metallic microfibers were systematically and detailedly investigated in this article. Experimental results indicated that the Gd-based microfibers prepared by the rotated-dipping process are uniform and continuous, with typically amorphous structure characteristics and favorable thermal stability. Curie temperature T C of Gd-based amorphous microfibers increases with the rising of Fe content, and the T C of GdAlCoFe3 microfibers is the highest at 128.7 K (relatively increased by 15.3 K than before doping). Among the general magnetic performance indicators, the saturation magnetization M s of GdAlCoFe2 microfibers reaches a peak at 264.04 emu/g. Furthermore, the values of magnetocaloric performance indexes of Gd-based amorphous microfibers increase firstly and then decrease with the rising of Fe-doping amount. When the external magnetic field H ex = 50,000 Oe, the maximum magnetic entropy change -Δ S m max, refrigeration capacity RC and relative cooling power RCP of GdAlCoFe1 microfibers are 10.33 J/kg·K, 748.22 J/kg and 1006.90 J/kg, which increased by 0.07 times, 0.13 times and 0.16 times, respectively than before Fe-doping (namely -Δ S m max = 9.68 J/kg·K, RC = 663.79 J/kg, RCP = 871.73 J/kg). From the perspective of microstructural changes, Fe-doping results in the formation tendency of atomic clusters and nanocrystals in micro-regions, the orderly orientation of atoms appears, and the magnetic anisotropy increases accordingly. In addition, the 3d electron layer of the doped Fe element in Gd-Al-Co-Fe quaternary alloy system enhances the RKKY indirectly exchange coupling interaction and changes the state of magnetic entropy, which in turn leads to an increase in Curie temperature and an improvement in magnetocaloric performance. Since RC and RCP are the main indicators in engineering applications, the GdAlCoFe1 amorphous microfibers can be selected as a low-temperature magnetic refrigeration working medium to provide technical guarantee for the application of magnetic refrigeration technology. In comparison to Fe-doped Gd-based amorphous microfibers, # GdAlCoFe1 microfibers have enhanced magnetocaloric properties by coactions of atomic arrangement ordering transformation (AAOT) and magnetic moment ordering transformation (MMOT). Image 1 • Influence of Fe-doping amounts on the magnetocaloric properties was investigated systematically. • MCE properties of # GdAlCoFe1 amorphous fibers were enhanced effectively. • Interaction mechanism was illustrated from the perspective of atomic arrangement and magnetic moment ordering transformation. [ABSTRACT FROM AUTHOR]

Ce 69 Al 10 Cu 20 Co 1 metallic glass was fully annealed to its metastable equilibrium supercooled liquid (MESL) state at a temperature below the calorimetric glass transition, i.e., sub- T g , and quenching/cryogenic combined treatment (Quenching + CT) was subsequently manipulated in liquid nitrogen. The evolution of glass transition, specific heat capacity (C p) and enthalpy change (Δ H) were investigated by differential scanning calorimetry (DSC). Rejuvenation phenomenon on the perspective of energy level was found compared with the relaxed state of the sample. The evolution of the structural states, including the free volume, internal stress and atomic clusters, that caused by the quenching process and subsequent cryogenic treatment is discussed and acted as the physical interpretation to the relaxation-to-rejuvenation transition. Image 1 • Quenching/cryogenic treatment performed at sub- T g induces rejuvenation in MGs. • Liquid nitrogen quenched Ce-based MG shows a recovery degree of enthalpy of 30%. • The subsequent cryogenic treatment with the time of 96h extends the recovery to 100%. [ABSTRACT FROM AUTHOR]

In this work, precipitation behavior and mechanical performances of A356.2 alloy (treated by Al–6Sr–7La composite refinement-modification agent) were studied for the first time. Artificial aging treatment (T6) and long-time natural aging treatment (>10,000 h, T4) were applied to clarify the precipitation and growth behavior of Mg 5 Si 6 phase. The results show that vacancies and dislocations formed during solution treatment promote the nucleation and growth of Mg 5 Si 6 phase in the eutectic area during the subsequent aging process. During the T6 treatment, the growth of Mg 5 Si 6 phase is promoted due to the interaction of atomic diffusion channel caused by higher Si concentration gradients and dislocations, leading to a large number of uniform distributed spherical Mg 5 Si 6 phase in eutectic area. While, for the T4 treated alloy, atomic clusters with short rod-like Mg 5 Si 6 phase exists inside the alloy. In addition, T6 treatment resulted in significant improvement of tensile strength (UTS), yield strength (YS) and vickers hardness (HV) compared with the T4 treated alloy and the reasons were discussed. • Precipitation behavior of A356.2 alloy (treated by Al–Sr–La) in eutectic area was clarified. • Precipitation mechanism of Mg 5 Si 6 both under T6 and T4 were found. • Mechanical performances of Al–Sr–La treated A356.2 alloy (treated by Al–Sr–La) were investigated. [ABSTRACT FROM AUTHOR]