Scripta Materialia最新文献

This study focuses on the impact of off-eutectic microstructures on mechanical properties in ternary Mo-Si-Ti alloys, namely Ti-rich Mo-18Si-72Ti and Mo-16.5Si-72Ti, in relation to the well-researched eutectic, two-phase Mo-20Si-52.8Ti alloy. The microstructure of these alloys consists of a Ti-rich body-centered cubic solid solution (Ti,Mo,Si)_ss and a hexagonal silicide phase (Ti,Mo)₅Si₃. Notably, the off-eutectic alloys exhibit remarkable compression ductility at 800 °C, distinguishing it from Mo-20Si-52.8Ti. The directionally solidified (DS) specimens of the Ti-rich alloys display higher strength compared to the arc-melted specimens. This enhanced strength is attributed to the multiple precipitation strengthening events present, despite the increase in the length scale of individual phases which further enhances the fracture toughness.

Glasses in the TeO₂-ZnO-Bi₂O₃ system were prepared with up to 2.5 mol% of Yb₂O₃ using standard melting process and their crystallization process was investigated for the first time. No concentration quenching was observed. The thermal treatment leads to surface precipitation of crystals, the composition of which depends on the Yb₂O₃ content. The addition of Yb₂O₃ in the tellurite network promotes the precipitation of Bi₂Te₄O₁₁ crystals at the expense of Zn₂Te₃O₈ crystals. The growing of these crystals in the low Yb³⁺ concentrated glass during a thermal treatment increases the interaction between the Yb³⁺ ions leading to an enhancement of the Yb³⁺ emission properties which reach those of highly Yb³⁺ concentrated tellurite glass. Our study suggests that a thermal treatment can be a practical alternative to increase the emission efficiency of the glass prepared with 0.5 mol% of Yb₂O₃ to the level of the as-prepared glass doped with 2.5 mol% of Yb₂O₃.

Interfacial behavior in composites significantly influences their properties. Ag-based composites reinforced with Ti₃AlC₂ (a MAX phase) are promising for electrical contacts. However, interdiffusion between the Ag matrix and Ti₃AlC₂ increases impurities in the Ag matrix, adversely affecting electrical resistance and raising operational temperatures. To address this, we developed a novel partial etching pretreatment that selectively etches Al atoms from the near-surface region of Ti₃AlC₂, creating a Ti₃C₂ surface layer. This innovative approach confines interdiffusion mainly within the Ti₃C₂ layer, preserving the Ag matrix's high electrical conductivity. Experimental results for Ag-based composites with 10 wt.% of Ti₃AlC₂, subjected to 0.5 h etching, show a significant 51 % reduction in electrical resistivity with only a 10 % decrease in mechanical properties compared to Ag/Ti₃AlC₂. These findings underscore the effectiveness of manipulating A-site elements in Ti₃AlC₂ to enhance the performance of Ag-based composites, offering valuable insights for advanced electrical material design.

Physical modeling and deep learning are known for their respective advantages in interpretability and computational efficiency. Nonetheless, efficiently predicting properties of metallic materials while maintaining interpretability presents a formidable challenge. This study proposes a novel solution by introducing dual-output deep learning model that simultaneously predicts stress-strain partitioning and mechanical properties through a two-component architecture. The initial component uses U-Net model trained on stress and strain partitioning generated from crystal plasticity (CP) simulations, thereby enhancing interpretability. Subsequently, this information is used to predict the properties in the second component. The prediction results demonstrate the validity of this approach, accurately predicting high stress at the martensite-martensite interface, high strain at the ferrite-martensite interface, and properties. In addition, the minimal computational cost significantly improves efficiency compared to conventional CP method. This innovative methodology represents a significant advancement, achieving harmonious balance between interpretability, computational accuracy, and efficiency in properties prediction of metallic materials.

The optical transmission, the wavelength and temperature dependence of the Verdet constant as well as the thermally induced depolarization in a Zn₄B₆O₁₃ crystal were investigated. The analytical dependence of the Verdet constant on wavelength and temperature, which describes well the experimental data in the 240–1100 nm range, was obtained. The small coefficient of linear expansion and its isotropy significantly suppressed thermally induced depolarization associated with thermally induced linear birefringence caused by the photo-elastic effect, while the diamagnetic nature of the material ensured the absence of thermally induced depolarization associated with the temperature dependence of the Verdet constant. The results revealed that Zn₄B₆O₁₃ is highly suitable for the wavelength range of 248–350 nm and can be used as a magneto-optical material for an optical isolator for high-average-power UV lasers.

The high cost of noble metal raw materials is a major limitation to the production of hydrogen from electrocatalytic water splitting. Nowadays, the poor activity and complex synthesis methods of non-noble electrocatalysts need to be urgently improved. Herein, we prepared the Fe-Si-B alloys with nanosheet structure on the surface by de-alloying process in KOH solution. Experimental results indicate that there are lots of B-doped Fe nanosheets on the surface due to the faster dissolution rate of Fe-Si phase in the alkaline solution. The small amounts of boron remaining and the oxidation of the Fe nanosheets could enhance the activity of the hydrogen evolution reaction (HER). The HER overpotential under 10 mA/cm² is 214 mV. The coordination between elemental components and the de-alloying process not only increased the electrochemical surface area, but also enhanced electrocatalytic activity of iron atoms. This work provides a new idea for the design of Fe-based electrocatalysts.

In this study, three-dimensional functionally graded NiTi bulk materials were fabricated using laser powder bed fusion (LPBF) by in-situ adding Ni powder into equiatomic NiTi powder. The gradient zone exhibited a Ni composition ranging from approximately 49.6 to 52.4 at.% over a distance of about 2.75 mm. The functionalities along the compositional gradient were examined through differential scanning calorimetry analysis and spherical indentation. This unique gradient resulted in location-specific functionalities, including superelasticity characterized by wide and narrow hysteresis loops, shape memory effect, and various phase transformation temperatures. The rapid cooling rate during fabrication led to the presence of excess Ni in the solid-solute state within NiTi. This unique solid-solute compositional gradient in NiTi resulted in varying lattice parameters, influencing the compatibility between martensite and austenite and allowing for tailored hysteresis. This discovery presents new avenues for designing multifunctional materials through in-situ additive manufacturing.

Kagome lattice, made of corner-sharing triangles, provides an excellent platform for hosting exotic topological quantum phases. Here, we report the observation of large anomalous Hall effect and topological Hall effect in the Kagome lattice material Yb_0.90Mn₆Ge_3.25Ga_0.39 single crystal. Compared to the antiferromagnetic pristine compound YbMn₆Ge₆, Yb_0.90Mn₆Ge_3.25Ga_0.39 has an easy plane ferromagnetic structure below 361 K and presents a spin-reorientation transition at 218 K. An intrinsic anomalous Hall conductivity with the value of 604.2 Ω^-1·cm^-1 is obtained in Yb_0.90Mn₆Ge_3.25Ga_0.39, which is the largest in RMn₆X₆ (X = Ge and Sn) family. Besides, a remarkable topological Hall signal is also observed near room temperature. The topological Hall resistivity of Yb_0.90Mn₆Ge_3.25Ga_0.39 is determined to be -1.86 μΩ·cm at 280 K under μ₀H = 0.3 T. Our results indicate that Yb_0.90Mn₆Ge_3.25Ga_0.39 may be an excellent platform to study the relationship between the magnetic and electronic structure and to explore novel quantum phenomenon.

The phase evolution in the transition zone (TZ) of TiAl/Ti₂AlNb dual alloy during laser-directed energy deposition (L-DED) process was investigated using in situ synchrotron radiation X-ray diffraction. The as-solidified microstructure of the TZ forms through the following phase transitions: Liquid→ Liquid + β/B2 →β/B2→ β/B2 + α₂. Thermal cycles promote the β/B2 to α₂ phase transition with the α₂ phase precipitates from the (011) plane of the β/B2 matrix during this transition. The phase transition sequence of the TZ during the first thermal cycle is: β/B2 + α₂ → β/B2 → β/B2 + α₂. The second thermal cycle leads to a partial transformation of β/B2 phase to α₂ phase. The TZ experiences no phase transition from the third thermal cycle. This study provides a comprehensive understanding of the phase formation mechanism in the TZ of L-DEDed TiAl/Ti₂AlNb dual alloys.

Significant effects of electric currents on mass transport in liquid metals have been observed for long, but the origin of the corresponding driving forces remains unclear in the literature. Without current, two driving forces induce mass transport in liquid metals. (i) A chemical force, coming from concentration gradients. In that case, mass transport occurs by diffusion. (ii) A physical force, resulting from density gradients thermally and/or chemically induced. Here, mass transport occurs by thermal and/or solutal convection. Under electric currents, these driving forces are modified, either by electrostatic or magnetic forces, the corresponding mechanisms being referred to as electroconvection and magnetoconvection, respectively. However, these mechanisms cannot easily be distinguished from each other, leading to confusion in literature. Here, it has been shown that, in the liquid Sn-Zn system, the driving force induced by 500–1000 A/cm² electric current densities is magnetic rather than electrostatic, the mechanism being therefore magnetoconvection.