Scandium Research Articles

Theoretical study of the effects of alloying elements on TiO2/Ti2AlNb interface adhesion properties.

Ti2AlNb-based alloys are expected to be applied in the manufacture of parts of aeroengines to achieve the goal of increasing the thrust-to-weight ratio. However, the poor high temperature oxidation resistance of these alloys may hinder their applications. Alloying has been proven to be effective in improving oxidation resistance properties. However, the selection of alloying elements and their influence mechanisms are rarely studied. The TiO2/Ti2AlNb interface bonding interactions and the effects of alloying elements of Si, Sc, Y, Zr, Mo and Hf were investigated via first principles calculations. The separation energy and electronic structure were studied to explore the bonding interactions between the oxide scale and Ti2AlNb matrix. When Zr and Hf are used to replace Al, the bonding properties of the TiO2/Ti2AlNb interface are improved. The tensile and shear deformations of the interfacial zones are applied to study the influence of alloying elements on the TiO2 oxide spalling on Ti2AlNb. The tensile strength is increased by more than 2 GPa when Nb is substituted by the Sc, Zr and Hf elements. Therefore, Sc, Zr, and Hf are beneficial for inhibiting oxide spalling and will have great potential to improve the oxidation resistance properties.

First-principles study of magnetic properties and electronic structure of 3d transition-metal atom-adsorbed SnSSe monolayers.

We investigated the electronic structure and magnetic characteristics of 3d transition metal elements (Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn) adsorbed onto monolayer SnSSe by employing first-principles calculations. After the calculation, we found that Sc, Ti, V, Cu, and Zn atoms adsorbed onto monolayer SnSSe do not have magnetic moments, while the rest of the atoms adsorbed onto SnSSe are able to produce magnetic moments, and their magnetic moments in the adsorption systems are in the range of 1.0-3.0 μB, in which the magnetic distance of Mn is the largest. The results of MAE calculations indicate that there is a big difference in the MAE of the systems with TM atoms adsorbed to the S-side and the Se-side; for V adsorbed to the S-side on the Sn atoms, the MAE is the largest, which reaches 8.277 meV f.u.-1, showing an in-plane magnetic anisotropy, and for Co adsorbed to the Se-side on the Sn atoms, the MAE is the smallest, which is -0.673 meV f.u.-1, showing a perpendicular magnetic anisotropy. Calculations of binding energies show that all atoms are able to adsorb stably. Our results indicate the potential application of TM-adsorbed SnSSe monolayers in spintronics and magnetic memory devices.

Rare Earth Element Characteristics of Shales from Wufeng-Longmaxi Formations in Deep-Buried Areas of the Northern Sichuan Basin, Southern China: Implications for Provenance, Depositional Conditions, and Paleoclimate.

To explore the sedimentary environment and the background of the source area of organic-rich shales in the Wufeng-Longmaxi Formations in the northern Sichuan Basin, samples from Well XX1 in the area were subjected to geochemical testing and analysis of organic carbon content, trace elements, and rare earth elements (REEs). The results show that the total content of REE (ΣREE) of the shale in the Wufeng-Longmaxi Formations varied from 183.08 to 234.66 μg/g with an average of 212.59 μg/g, which is significantly higher than the content of the North American shale composite. The fluctuations in the total amount of REEs in the shale of the Wufeng-Longmaxi Formations reflect certain differences in the geochemical conditions of the Upper Ordovician-Lower Silurian shale. The ratios of LREE/HREE, LaN/YbN, LaN/SmN, and GdN/YbN and the distribution of normalized REE patterns indicate that the source supply or sedimentary structural background may have changed during the shale deposition period of the Wufeng Formation, while the shale deposition period of the Longmaxi Formation may be in a relatively stable source supply and sedimentary structural background. There is no significant correlation between δCe and ΣREE, and the obviously negative Eu abnormity and the weak Ce abnormity indicated that the diagenesis had a limited impact on REEs. Geochemical parameters such as values of ∑REE, δEu, δCe, Ceanom, and LaN/YbN indicate that the climate during the Wufeng-Longmaxi Formation shale deposition period was warm and humid, and the shale was deposited mainly in the suboxic-anoxic water environment. The deposition rate was stable and slow, providing good conditions for the production and preservation of organic matter. At the same time, this shows that the water environment of Wufeng Formation is more anoxic and reductive than that of Longmaxi Formation, which is more conducive to the preservation of organic matter. The correlation between ΣREE and the content of Sc, Ti, Cr, Co, Zr, Nb, Th, Hf, Ta, and other elements indicates that the sources of REEs in the shale of Wufeng and Longmaxi Formations in the study area are similar, mainly terrestrial clasts, and some may come from the sea. The REE distribution pattern shows that the shale provenance of the Wufeng-Longmaxi Formations mainly comes from the upper crust. The La/Yb-∑REE diagram shows that the sediment-parent rocks are mainly early sedimentary rocks and these sediment-parent rocks have granite provenance characteristics. Compared to La/Yb, LREE/HREE, LaN/YbN, and other REE characteristic parameters, it is inferred that the tectonic background of the study area is dominated by passive continental margin.

Review of temporal trend in Archean granitoid chemistry- implications for Eoarchean (3.7–3.9 Ga) transition in geodynamic regime of crust formation

In this study, we review changes in Archean granitoid chemistry using stacked probability density estimation and statistical change-point analyses. A significant change in Archean sodic granitoid composition occurs in the 3.9–3.75 Ga period, marked by a shift of SiO2, Al2O3, Na2O, V, Cr, Sr, Sr/Y to higher, and TiO2, FeOT, MnO, P2O5, A/NK, A/CNK, Sc, Ba, Ta, Nb, Hf, Y, and rare earth elements to lower values, which reflects different formation P-T regime and petrogenetic processes. Using phase equilibria and trace element modelling, we demonstrate that the pre-3.9 Ga Acasta Tonalite Gneiss (ATG)-like granitoids formed at shallow depths (∼3 km) but are chemically distinct from impactites of all known large impact craters with basaltic/mixed target rocks. Impact melting produces MgO-rich melts at relatively greater “apparent” depths, reflecting target rock chemistry and contribution from the upwelling mantle, and is unlikely to have produced the shallow-seated ATG rocks. The ATG trace element chemistry is similar to many modern-day non-arc settings felsic rocks, which suggests that the melting regime in these extensional settings also existed before 3.9 Ga and ATG formed in a mantle plume-driven extensional tectonic regime involving melting of long-lived mafic proto-crust at shallow crustal depths above mantle upwelling. In contrast, the 3.9–3.75 Ga transitional and post-3.75 Ga TTGs formed by deep-seated (25–50 km) melting in equilibrium with garnet-bearing amphibolite. When considered together with Ti isotopic evidence of shift from tholeiitic to calc-alkaline magmatism in the 4.0–3.75 Ga period, the evidence for a transition from a regime dominated by crustal reworking to one of significant juvenile input at 3.60–3.85 Ga, noted in trace element/Hf-isotope composition of detrital zircon from several cratons and the reported ultra-high pressure metamorphism/interleaving arc-plume sequence, require a greater depth of melting. We interpret this transition to mark a gradual shift from stagnant-lid to intermittent mobile-lid-type plate tectonics involving deeper subduction of oceanic lithosphere. However, from the single occurrence of pre-3.9 Ga ATG rocks and their similarity with some Archean Fe-rich silica-saturated rocks chemistry, it is unknown whether plume magmatism was the only active mechanism or operated in conjunction with mobile-lid tectonics on early Earth, like in Archean.

Enhancing the strength of Sc-containing Al-Cu-Li alloys by modifying the precipitation behavior through plastic deformation and heat treatment

Al-Cu-Li alloys are used extensively in the aerospace manufacturing industry for their outstanding properties, however, the addition of trace Sc elements will form high-temperature insoluble (Cu, Sc)-containing phases during homogenization leads to a decrease in age-strengthening, and there is a limited investigation on how to overcome this unfavorable factor. In this work, the effects of plastic deformation coupled with heat treatment on the microstructure and mechanical properties of Sc-containing Al-Cu-Li alloy were systematically investigated by using age-hardening curves and room-temperature tensile tests combined with characterization by TEM, EBSD, and SEM/EDS. The results show that plastic deformation before high-temperature treatment fragments and promotes the dissolution of coarse phases, reduces the development of (Cu, Sc)-containing enriched phases, and simultaneously increases the content of Cu atoms within the Al matrix. Among all precipitates (GPB zones, S phases, T1 phases) after T6 aging, T1 phases act as the dominant strengthening phase of the alloy. At the same time, we found that the decrease in the Cu-containing residual phase after solid solution treatment will result in a remarkably increasing number density and volume fraction of T1 phases at the peak aging. In a word, we obtain a good strength-ductility trade-off (the yield strength is ∼500 MPa while maintaining ∼10% elongation) Al-Cu-Li alloy with Sc element by optimizing the distribution of Cu elements and modulating the aging precipitation behavior. Our proposed process is expected to provide an experimental and theoretical guide toward the development of Al-Cu-Li alloys with superior properties.

Effect of Sc micro-alloying on microstructure and corrosion behavior of 7085 alloy friction stir welded joints

The corrosion resistance of 7085 and 7085Sc alloys FSW joints was studied by discussing intermetallic compounds, surface oxide film and grain boundary. It shows that Sc-containing Cu-rich phase and Al3(Sc,Zr) would form in 7085Sc alloy, which reduces the size of pitting sources, and is conducive to inhibiting the micro-galvanic corrosion of intermetallic compounds. Secondly, Sc element can promote the formation of a more stable oxide film on the surface, thereby reducing the corrosion rate of 7085Sc alloy. After FSW of the two alloys, the HAZ region produces a Cu-poor zone between GBPs and adjacent matrix due to the coarsening of grain boundary precipitates, which increases the micro-galvanic corrosion effect and easily leads to strong intergranular corrosion behavior. The intergranular corrosion of WNZ is mainly caused by the potential difference between GBPs and the matrix in the grains. The corrosion potential of each micro area of 7085Sc alloy welded joint is improved, and the corrosion resistance is more excellent. This is mainly due to the high proportion of low angle grain boundaries in each region, the decrease of Cu element difference on HAZ grain boundaries, and the decrease of potential difference between GBPs and intragranular in WNZ.

Correlation between pitting susceptibility and surface acidity, point of zero charge of passive film on aluminum: Influence of alloying elements

The pitting potential, intrinsic surface acidity, point of zero charge of passive film on Al are studied using first-principles calculations to establish their relationships. Influences of alloying elements Zn, Cr, Nb, Si, Mo and Sc on adsorption of NH3 and NaCl, pHpzc of Al2O3 and pitting susceptibility of Al are investigated. The efficiency for enhancing pitting resistance of Al is evaluated, yielding the ratios Si: Zn: Cr: Mo: Nb: Sc = 1.8: − 0.3: 1: 1.9: 1.4: 0.2. A model for the dependence of pitting potential on the concentration of alloying elements in Al alloy matrix is developed, based on effects of alloying elements on the surface charge of passive film. The effects of Sc on pitting potential and pHpzc of Al oxide are predicted based on the calculated results, which are supported by electrochemical measurement, XPS analysis and contact angle titration.

Rare earth elements in the red, brown, green algae and the seagrass from Kazachya Bay (Crimea, Black Sea)

The present study is focused on the first ever quantification of rare earth elements (REE) in four mass plants of the Black Sea coast of Crimea: the brown alga Gongolaria barbata, the green alga Ulva rigida, the red alga Ceramium ciliatum, and the seagrass Zostera noltei using inductively coupled plasma mass spectrometry. The REE contents in the macrophytes were found to be one to two orders of magnitude lower than in the sediments. In the plants, three groups of REE with similar levels have been identified. The first group included the most abundant elements Sc, Y, La and Ce; the second group consisted of Pr and Nd with the intermediate contents; and the third group contained the elements with the lowest contents: Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu. The contribution of light REE (Sc, Y, La, Ce, Pr, Nd) to the total REE content in the plants was 91–96%. The highest REE levels were found in the red alga and seagrass rhizomes. Higher translocation factors of Sc, Pr, La, Ce and Tb between seagrass rhizomes and leaves were noted. In terms of the REE content decrease, the marine plants are arranged in the following order: seagrass rhizomes > red alga > brown alga > seagrass leaves > green alga. Brown algae attached to the rocky seabed are widespread in the upper sublittoral, have a long lifespan, and accumulate relatively high amounts of REE. Therefore, they can be used as effective bioindicators of REE pollution in the marine environment.

Influence of departures from LTE on determinations of the scandium abundances in A–B-type stars

ABSTRACT We developed a comprehensive model atom of Sc ii–Sc iii. Abundances of scandium for a sample of eight unevolved A9–B3-type stars with well-determined atmospheric parameters were determined based on the non-local thermodynamical equilibrium (NLTE) line formation for Sc ii–Sc iii and high-resolution observed spectra. For the Sc ii lines, the abundance differences between NLTE and local thermodynamical equilibrium (LTE) grow rapidly with increasing effective temperature (Teff), from slightly negative at Teff = 7250 K to positive ones of up to 0.6 dex at Teff = 10 400 K. For Sc iii in ι Her, NLTE reduces the line-to-line scatter substantially compared to the LTE case. The NLTE abundances of Sc in our five superficially normal stars are consistent within the error bars with the Solar system Sc abundance, while the LTE abundances of the late B-type stars are greatly subsolar. NLTE reduces but does not remove a deficiency of Sc in the Am stars HD 72660 and Sirius. Based on our own and the literature data, the Ca/Sc abundance ratios of the sample of 16 Am stars were found to be close together, with [Ca/Sc] = 0.6–0.7. We propose the Ca/Sc abundance ratio, but not the abundances of individual Ca and Sc elements to be used for classifying a star as Am and for testing the diffusion models. We provide the NLTE abundance corrections for 10 lines of Sc ii in a grid of model atmospheres appropriate for A to late B-type stars.

Introduction of rare-earth element Sc in alloy design to modify wear features of dual-phase high-entropy alloy

Introduction of rare-earth element Sc in alloy design to modify wear features of dual-phase high-entropy alloy

Achieving ultra-high corrosion-resistant Mg-Zn-Sc alloys by forming Sc-assisted protective corrosion product film

The weak corrosion resistance of magnesium and its alloys greatly limited the industrial application. Though functional self-healing coatings have been proposed as countermeasures, repeated damages on coatings under practical installation and complex external environments could require self-adaptive corrosion protection against multiple abrasions. In this study, an ultra-high corrosion-resistant Mg-1Zn-1Sc (wt.%) alloy with a corrosion rate of 0.087 mm/y has been designed and prepared, which has fine grains and uniform structure of a nano-scale ScZn phase with low potential. A unique and dense corrosion product film with a three-layered structure was found and studied on Mg-1Zn-1Sc alloy, providing excellent corrosion protection. In addition, the formation and protection mechanisms of the three-layered corrosion product film on Mg-1Zn-1Sc alloy have been discussed and proposed. The growth behavior of protective corrosion product film could be driven by the synergy of Sc and Zn elements. Furthermore, with the increase of Sc content, the strength, plasticity, and corrosion resistance of Mg-1Zn-xSc (x = 0, 0.2, 0.6, 1.0, in wt.%) alloys increased simultaneously. The high corrosion resistance and moderate mechanical performance qualify Mg-1Zn-1Sc alloy as a promising candidate for diverse industrial applications.

Synergistic reinforcement of in situ ZrB2 particles and Sc on the corrosion behaviour of 7N01 alloy

In this study, the effects of in situ ZrB2 particles and rare earth element Sc on the corrosion behavior of 7N01 alloy were investigated separately, with the characteristics of their synergistic enhancement being elucidated. The introduction of Sc into the ZrB2/7N01 composites led to an enhancement in both the distribution and morphology of the in situ particles, with the size of ZrB2 particles being significantly reduced and large particle clusters almost disappearing compared to the situation without Sc addition. A decrease in the grain size of the matrix alloy 7N01 from 170 μm to 33 μm was also observed when the Sc addition was 0.5 wt%. The low corrosion susceptibility observed after the addition of Sc was attributed to the refinement of grains and the inhibition of the formation of precipitate-free zones. The addition of ZrB2 improved corrosion resistance by promoting the precipitation of Al3Sc precipitates. Importantly, it was found that the 7N01 alloy with 3 wt% ZrB2 and 0.5 wt% Sc exhibited high mechanical properties and admirable corrosion resistance, which makes it a promising material for various applications. In summary, this study highlighted the individual and combined effects of in situ ZrB2 particles and rare earth element Sc on the corrosion behavior of 7N01 alloy, with valuable insights being provided for the development of advanced structural composite materials.

Alteration of chromite during serpentinization of peridotites

Trace element (Zn, Co, Mn, Ni, Ga, V, Ti, and Sc) compositions of chromite in mafic-ultramafic rocks are widely used for addressing their petrogenesis and discriminating tectonic environments, but they can be altered by subsolidus re-equilibration and hydrothermal alteration, and the detailed dynamic processes are not clear. The Jinchang ophiolite in SW China is part of the Tethyan ophiolite, and consists mainly of harzburgite with minor lherzolite. These peridotites are strongly serpentinized, and contain variably modified chromite and magnetite. Two types of chromite are identified in harzburgite, including magmatic and altered chromite. The magmatic chromite occurs as granular or amoeboid minerals, or as cores surrounded by the altered chromite, and they have homogeneous major elemental compositions (Mg0.65Fe0.35(Cr0.46Al0.54)2O4), but their trace elements, such as Ni, Ga, V, Zn, Co, and Mn, are variably changed during subsolidus re-equilibration. The altered chromite consists of ferrous chromite (Mg0.15Fe0.85(Cr0.46Al0.11Fe0.43)2O4) and chromian magnetite (Fe(Cr0.15Fe0.85)2O4), which were formed by two stages of hydrothermal alteration. They are depleted in Ga and Sc, and enriched in Zn, Co and Mn during the alteration, but their Ti, Ni and V are increased and decreased in the first and second stage, respectively. Thermodynamic modeling reveals that: (1) Reaction between magmatic chromite and olivine at the first stage of alteration produces ferrous chromite and chlorite under high temperature (610–470 °C) and increasing oxygen fugacity (ΔFMQ increasing from −1 to 3) and water-rich conditions; (2) Chromian magnetite is generated by further alteration of the ferrous chromite in the second stage alteration under low temperature (< 470 °C) and decreasing oxygen fugacity conditions (ΔFMQ decreasing from 3 to −4). In addition, the first stage alteration significantly changed trace-element compositions of the magmatic chromite compared with the second stage alteration that slightly modified the ferrous chromite. This study clarifies trace element migration of chromite in the silicate mineral-hydrothermal fluid system, indicating that chromite microstructures and trace elemental compositions can record the detailed serpentinization processes.

Design of novel Al-Mg-(Zn-Sc) alloys with enhanced mechanical properties and corrosion resistance

The novel Al-Mg-(Zn-Sc) alloys were fabricated using vacuum induction melting and argon-protected casting method. The effects of Zn and Sc on the microstructure evolution, mechanical properties and corrosion properties of the as-cast Al-Mg-(Zn-Sc) alloys were comparatively studied. The results show that the addition of 1.5 wt% Zn facilitates the evolution of coarsen β-Al3Mg2 phases into fine T-Mg32(Al, Zn)49 phases, enhancing the resistance to intergranular corrosion (IGC) of Al-5.5Mg-1.5Zn-0.4Sc (alloy 4) with a maximum corrosion depth of 133.4 µm. The addition of Zn also promotes Mg solid solution, resulting in a 13.7 % increase in Mg solid solution concentration in Al-5.5Mg-1.5Zn (alloy 3) compared to Al-5.5Mg (alloy 2). The addition of 0.4 wt% Sc leads to the formation of smaller (∼2 µm) Al3Sc particles with a larger volume fraction of 0.96 %, providing grain refinement and improved strength in the Al-Mg alloy. Furthermore, the joint addition of Zn and Sc elements reduces the grain size by 64.0 % compared to Al-5.0Mg (alloy 1) and increases the tensile strength by 33.5 %. Alloy 4 exhibits the greatest measured tensile strength of 343 MPa. The solid solution strengthening, grain boundary strengthening and precipitation strengthening contributions to alloy 4 are calculated at 76.8 MPa, 27.9 MPa and 66.6 MPa, respectively.

Search for Toxic Trace Elements in Rosa rugosa Thunb. By Instrumental Neutron Activation Analysis: Accumulation and Responses to Exposure

Species of the genus Rosa L. are widely used in urban gardening, and they are of considerable interest as plants accumulating heavy metals in an urban environment. Literature data are ambiguous about whether these species accumulate trace and toxic elements. Its fruits are used as medicinal raw materials in folk and official medicine. The purpose of the study is to determine whether this type of wild rose accumulates toxic metals (as well as various macro- and microelements), if so, which ones and in which organs, and to what extent raw materials of the plant can be used. For the first time, multi-element instrumental neutron activation analysis at the reactor IBR-2 of FLNP JINR in Dubna, Russia, was applied to examine accumulation of major and trace elements in various organs of Rosa rugosa Thunb. (Rosaceae family), namely, roots, leaves, fruits and seeds. A total of 33 elements (Al, Ca, Cl, I, Mg, Mn, V, As, Br, K, La, Na, Mo, Sm, U, W, Ba, Ce, Co, Cr, Cs, Fe, Hf, Ni, Rb, Sb, Sc, Sr, Ta, Tb, Th, Yb, and Zn) were determined. Samples were taken in the summer-autumn period of 2020, both in the city of St. Petersburg and on the coast of the Baltic Sea, Russia. This research found no critical accumulation of trace and toxic elements in different organs of R. rugose, but revealed quite high accumulation of Fe and Co in urban transport highway area.

Groundwater trace element changes were probably induced by the ML3.3 earthquake in Chaoyang district, Beijing

Geochemical composition changes in groundwater related to earthquakes have been documented in previous studies, and most such studies focused on the changes in major ions, hydrogen, oxygen isotopes, and geochemical gases. Changes in trace elements were suggested to be more sensitive to small earthquakes than the commonly used chemical constituents such as major ions, yet they received less attention. Beijing is located in the Zhangjiakou-Bohai seismic belt and experiences frequent occurrences of small earthquakes. In this paper, we collected groundwater samples from a hot spring in Yanqing district of Beijing weekly from August 2021 to August 2022. Each water sample contained 41 trace chemical compositions. During the sampling, an earthquake with a magnitude of ML3.3 occurred in the Chaoyang district of Beijing on 3 February 2022, so these trace elements changes were systematically monitored before and after the earthquake: Li, Sc, Ti, and Pb elements had upward changes before the earthquake, while Cu, Nb, Th, Zn, Tl, and U elements had downward changes before the earthquake. Eu (rare earth elements) had upward changes after the earthquake. At the same time, the earthquake caused no significant changes in the groundwater level in the seismic monitoring well near the Songshan spring. Such responses indicate that trace elements are likely to be more sensitive to crustal strain than groundwater level. We considered that the earthquake-induced rock cracks before or after the earthquake caused enhancing water-rock interaction and led to the migration of trace elements between the water column and rocks, which is the mechanism to explain the trace elemental changes. This study probably provides a comprehensive assessment of the sensitivity of trace element constituents to the earthquake. Furthermore, we suggest that more long-term continuous monitoring and research of trace elements in Beijing and Zhangjiakou-Bohai Fault Zone should be considered to explore the response mechanism of groundwater geochemistry to earthquakes in the future.

Effect of rare-earth elements on the interface of WC/α-Fe cemented carbide: A first-principles calculation

The fundamental effects of rare-earth elements doping on cohesion properties of WC (101¯0)/α-Fe (100) interfaces were investigated by first-principles calculation. The WC/Fe interface has six interface structures, including W-AS-Fe, W-HS-Fe, W-BS-Fe, C-AS-Fe, C-HS-Fe, and C-BS-Fe interfaces. The C-BS-Fe interface is the most stable among all interface structures, with a maximum interface energy of 10.50 J/m2, due to the dominant FeCr covalent bond. Rare-earth elements (Sc, Y, La, Pr, Nd, Eu, Gd, and Dy) doped at three kinds of positions of the C-BS-Fe interface were investigated. The results show that the interfacial structural strength can be enhanced by Sc and Pr doping to Fe positions, and Nb can play a role in interfacial strengthening no matter which position is doped. Besides, the strengthening effect is the best when the subsurface Fe atomic position is replaced, which is on account of the formation of the FeNd metal bond and the NdC bond.

Effect of Sc on the microstructure and mechanical properties of ZrB2 particles reinforced spray formed 7055 aluminum alloy TIG welded joint

Adding nano ceramic particles to the weld seam is an effective way to improve the strength of the spray formed 7055 aluminum alloy welded joint. However, nano ceramic particles are prone to agglomeration, and the agglomerated nano ceramic particles in welded joint can cause stress concentration and brittle fracture of the specimen. In order to improve the aggregation of nano ZrB2 ceramic particles in the weld seam and further improve the mechanical properties of spray formed 7055 aluminum alloy TIG welded joint, Sc/ZrB2-7055 (SZ7) and ZrB2-7055 (Z7) welded joints were prepared in this study. Compared to the Z7 weld seam with coarse grains and severe aggregation of ZrB2 particles, the SZ7 weld seam has fine grains, and the distribution of ZrB2, Al3(Sc, Zr), and Sc modified ZrB2 particles in the weld seam was more uniform. The tensile strength and elongation of Z7 welded joints were 281 MPa and 2.0%, while the tensile strength and elongation of SZ7 welded joints were 320 MPa and 4.9%. The tensile strength and elongation values of SZ7 welded joints have increased by 13.8% and 145% respectively compared to Z7 welded joints. Sc elements formed a rich Sc layer on the surface of ZrB2 particles, which passivated the sharp corners of ZrB2 particles and increased the wettability between ZrB2 particles and Al liquid, resulting in uniform distribution of ZrB2 particles in the weld seams. Fine grain strengthening, dispersion strengthening, and dislocation strengthening are the main reasons for improving the mechanical properties of SZ7 welded joints.

Advancing Bulk Metallic Glass Formation: Utilizing Rare-Earth Elements in Zr-Based Alloys

Zr-based bulk metallic glasses (BMGs) are characterized by excellent glass-forming ability, combined with superior mechanical properties. However, oxygen impurities degrade both these aspects as oxides serve as heterogeneous nucleation sites during solidification. Rare-earth elements (REEs) are known to be good oxygen scavengers, binding oxygen to less harmful forms. The most stable rare-earth oxide (REO) is M2O3, which occurs in three polymorphic forms, depending on the radius of metal cation: cubic, hexagonal, and monoclinic. Here, we show the effect of Sc, Y, Lu, Nd, and Gd additions in relation to the oxygen content on the glass-forming ability of the Zr52.5Cu17.9Ni14.6Al10Ti5 alloy. Microscopic observations (SEM) supported by chemical analysis (EDS, WDS), structure identification (XRD), and thermal analysis (DTA) were carried out. The critical diameter for glass formation (Dc) in the high oxygen alloy doped with cubic oxide-forming elements (Sc, Y, and Lu) can be even higher (Dc = 9 mm) compared to the undoped alloy synthesized from low oxygen components. Therefore, we have demonstrated that it is feasible to produce BMG using low-purity constituents with REE-based oxygen scavengers. This bridges the gap between laboratory development and cost-effective commercial applications.Graphical

MgSc2Se4 Solid Electrolyte for Rechargeable Mg Batteries

MgSc2Se4 is among the most promising magnesium-ion solid electrolyte, as it possesses a high room temperature Mg+2 conductivity (~ 10-4 S/cm). However, MgSc2Se4 is also demonstrating a considerably high electronic conductivity (10-5 to 10-8 S/cm). Such high electronic conductivity restricts the applications of the material in all solid-state Mg-ion batteries. Efforts to lower the electronic conductivity via the enrichment of the material with selenium aliovalent doping, were not successful thus far. This suggests that the electronic conductivity may follow a model, which is different from a common model of charge transfer by electrons in a conduction band of the wide band gap semiconductor MgSc2Se4. Here, we will discuss and present data showing that the electronic transport in the Mg-Sc-Se ceramic is facilitated via the Berthelot-type conductivity mechanism. This suggests an electronic transport through a low-conducting matrix stuffed with nano-scaled free electron-containing regions. These inclusions are well-distributed across the Mg-Sc-Se, and the electronic transport takes place via electron tunneling between these conductive regions, through low-conducting matrix spacers. It is shown that these conductive zones, being comprised of elemental metallic Sc and ScSe mix, behave as a metallic-type electronic conductor. The nature of these conductive inclusions and the synthetic parameters controlling the appearance of such conductive areas will be discussed, as well as routes to minimize their formation.