Scripta Materialia最新文献

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 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.

Keeping adequate strain hardening to postpone plastic instability to a larger tensile strain is a stiff challenge in alloys with high yield strength. This study showed the feasibility of activating deformation twins (DTs) to ductilize an ultra-strong medium-entropy alloy (MEA) through microstructural design. High content (∼24 %) γ'' precipitates were introduced into a Ni_49.9Fe₃₃Cr₁₀Nb₄Ta₃B_0.1 (at.%) MEA to offer high yield stress. We found that increasing the γ'' precipitate size and spacing successfully activated DTs, contributing to a sustainable strain hardening of the alloy. Accordingly, an ultrahigh tensile yield stress (YS) of 1.55 GPa and ultimate tensile stress (UTS) of 1.7 GPa, along with a fracture elongation of 14.5 % were achieved in the MEA. We further demonstrated that compared to lowering the stacking-fault energy (SFE), increasing γ'' precipitate spacing significantly reduced the critical shear stress for triggering twinning partials in a nanoscale γ/γ'' system.

In this work, the crystallization path and non-isothermal kinetics upon heating of the Zr_59.5Cu_14.4Ni_11.6Al_9.7Nb_4.8 metallic glass were investigated. The devitrification process consists the formation of phases in the sequence of icosahedral quasicrystal (IQ) phase, Ni-containing phases, and Cu-containing phases. Avrami exponents were calculated at various heating rates, providing insights into the non-isothermal crystallization kinetics. The IQ phase and Ni-containing phases are interface-controlled growth, while the Cu-containing phases are diffusion-controlled growth. In addition, a continuous heating transition (CHT) diagram with a heating rate range exceeding six orders of magnitude was constructed, and the crystallization mechanism under different heating rates was revealed. These findings enrich the understanding of crystallization path and kinetics of metallic glass.

There is considerable interest in magnetic materials which also possess good mechanical properties. Hence, the effect of Ti/Al ratio on the microstructure, mechanical and magnetic properties of (FeCoNi)₉₀Ti_10-xAl_x complex concentrated alloys (CCA) was investigated. An increase in the Ti/Al ratio in these CCA enhanced chemical ordering and substantially improved selected mechanical and magnetic properties. As the Ti/Al ratio changed from 10 to 0, the ductility increased from 7.5 to close to 50 %, the saturation magnetization (M_s) increased from 115.2 to 136.7 emu/g, and the coercivity (H_c) decreased from 17.9 to 4.2 Oe. The Fe₃₀Co₃₀Ni₃₀Ti₅Al₅ alloy exhibit higher UTS×EL value than available soft magnetic materials and has relatively higher M_s and lower H_c compared with other CCA. These results provide a methodology to modulate the chemical order in the Fe-Co-Ni system by Al and Ti additions and synergistically tune the mechanical and magnetic properties for high performance rotating electrical machine applications.

Hydrogen-induced variations in mechanical behavior of zirconium alloys impose detrimental influence on nuclear fuel cladding integrity. This work reports a disappearance of intrinsic yield drop in a recrystallized zirconium alloy following hydrogen-charging treatment. Microstructure characterizations reveal that the nano-hydrides precipitation, mediated by second phase particles Zr(Fe,Cr)₂ acting as hydrogen trapping sites, leads to emission of substantial dislocations in α-matrix grains due to strong strain concentrations, as identified by high-angular resolution EBSD. These mobile dislocations preserved at elevated temperatures can maintain the applied plastic strain and impede rapid dislocation multiplication as well, a conclusion validated by comparative analysis of dislocation densities prior to and near yielding stage. These findings are expected to shed light on the underlying mechanisms governing the interaction between hydrogen and microstructural defects in Zr-based nuclear fuel cladding materials.