Acta Metallurgica Sinica-English Letters最新文献

This study focuses on developing a novel multiphase stainless steel with enhanced ductility and an ultralow yield ratio achieved through solid-solution treatment. The steel exhibits remarkable mechanical properties: a tensile strength of approximately 1114 MPa, an ultralow yield ratio of 0.36, exceptional uniform elongation of approximately 17.48%, and total elongation of approximately 21.73%. The remarkable ductility of the steel can be attributed to the transformation-induced plasticity (TRIP) effect observed in the retained austenite, while its exceptional strength results from the combined effects of TRIP and the martensite phase.

Transition metal sulfides (TMS) hold great promise as anode materials for Li⁺/Na⁺ storage. However, their practical application still faces several challenges, such as inadequate electrical conductivity, substantial volume changes and a propensity for agglomeration. To tackle these challenges, a 3D composite structure composed of graphene nanosheets crosslinked core−shell FeS₂@N, S co−doped porous carbon (FeS₂@NSC/GNs) is created by combining self−template polymerization with the graphene encapsulation technique. Systematic characterization and analysis demonstrate the effectiveness of the self−template polymerization strategy in generating a porous core−shell structure, which facilitates the uniform dispersion and optimal contact of the FeS₂ core within the carbon shell. Concurrently, the integration of graphene, alongside the porous carbon shell, introduces a sophisticated dual−protection mechanism against volume expansion and undesirable FeS₂ aggregation. Furthermore, the resulting 3D architecture enables efficient electron/ion transport and provides abundant sites for Li⁺/Na⁺ storage. Leveraging these inherent benefits, the FeS₂@NSC/GNs composite exhibits significantly improved lithium/sodium storage performance in comparison to the counterparts. Evidently, our proposed approach offers valuable guidance for the construction of advanced anodes for lithium/sodium−ion batteries.

We report a facile solution method to form titanium oxide (TiO₂) nano-flower structure on the titanium (Ti) substrates for realizing good physical sterilization and biocompatibility. We first prepare TiO₂ nanotubes (NT) with a diameter of about 80–100 nm and a length of about 5 μm on Ti substrates by anodization, which is utilized as precursor. Then, we employ immersion treatment in different concentrations of phosphoric acid solution at 75 °C for 5 h to realize the transformation from TiO₂ NT to TiO₂ nano-flower structure. In addition, we studied the effects of phosphoric acid concentration (1 wt%, 2.5 wt%, 5 wt% and 10 wt%) on the TiO₂ nano-flower structure, and the antibacterial properties and biocompatibility of the TiO₂ nano-flower structure. The results show that TiO₂ nano-flower structure become larger and thicker with the increase in the phosphoric acid concentration, and the thickness of the coating can reach 6.88 μm. Meanwhile, the TiO₂ nano-flower structure shows good physical sterilization effect, especially for the TiO₂ nano-flower structure formed in 10 wt% H₃PO₄ solution, the antibacterial rate can reach 95%. In addition, the TiO₂ nano-flower structure have no toxicity to the osteoblasts and support cell growth.

High-entropy alloys exhibit significant potential for application in the nuclear industry owing to their exceptional resistance to irradiation, excellent mechanical properties, and corrosion resistance. In this work, the Mo_0.5V_0.5NbTiZr_x (x = 0–2.0) high-entropy alloys containing alloying elements with low thermal neutron absorption cross section were designed and prepared. The crystal structure, microstructure, mechanical properties and corrosion resistance of the studied alloys were investigated. All the alloys possess a body-centered cubic crystal structure, which is consistent with the CALPHAD (acronym of CALculation of PHAse Diagram) modeling results. The addition of Zr does not alter the crystal structure of the Mo_0.5V_0.5NbTiZr_x alloys; however, it leads to an increase in the lattice constant as Zr content increases. The addition of Zr initially enhances the yield strength, but subsequently leads to a decline as the Zr content increases further. Specifically, the corrosion resistance of the Mo_0.5V_0.5NbTiZr_x alloys in superheated steam at 400 °C and 10.3 MPa decreases with the increase of Zr content. The effect of Zr content on the phase formation, mechanical properties and corrosion resistance of the Mo_0.5V_0.5NbTiZr_x high-entropy alloys are discussed. This study has successfully developed a novel Mo_0.5V_0.5NbTiZr_0.25 high-entropy alloy, which demonstrates exceptional properties including high yield strength, excellent ductility, and superior anti-corrosion performance. The findings of this research have significant implications for the design of high-entropy alloys in nuclear applications.

Joining dissimilar Mg/Cu alloys was still an intractable problem because of the excessive intermetallic compounds (IMCs) and poor mechanical properties using conventional welding methods. In the present study, friction stir welding was employed for the butt joining of dissimilar AZ31B Mg-alloy and T2 pure Cu plates. Defect-free Mg/Cu joints were obtained with Mg-RS and Cu-AS configuration, at a welding speed of 50 mm/min and tool rotating speeds of 325 r/min, 625 r/min and 925 r/min. At the joining interface, both Mg₂Cu and MgCu₂ IMC phases were observed, with a clear, uniform and continuous IMCs layer composed of two sub-layers, layer-A of Mg + Mg₂Cu and layer-B of Mg₂Cu + MgCu₂. The maximum ultimate tensile strength of the Mg/Cu friction stir welding joint reached 130 MPa at 925 r/min due to enhanced mechanical interlocking between Mg and Cu, as well as sufficient metallurgical bonding at the joining interface with an IMCs layer thickness in the range of 1.0–2.0 μm.

The effects of B addition on microstructure and mechanical properties of a γ′-strengthened CoNi-base superalloy are investigated. The addition of B leads to a substantial increase in the volume fraction of both the eutectic structure and borides. The CoNi-base alloy shows a high solubility limit for the element B. Borides become noticeable in the area surrounding the eutectic structure after the B level exceeds 0.46 at.%. It is found that the compression property and stress rupture life of the 4W2Ta alloys exhibit an initial rise followed by a subsequent drop as the B content gradually increases from 0.08 to 0.78 at.%. The 4W2Ta0.46B alloy demonstrates the most excellent high-temperature strength and stress rupture life, revealing that a moderate amount of B in the alloy noticeably enhances its mechanical properties by enhancing the grain boundary cohesion.

The hot deformation behavior of a newly developed Ni–W–Cr superalloy for use in 800 °C molten salt reactors (MSRs) was looked into by isothermal compression tests in the temperature range of 1050–1200 °C with a strain rate of 0.001–1 s⁻¹ under a true strain of 0.693. An Arrhenius-type model for the Ni–W–Cr superalloy was constructed by fitting the corrected flow stress data. In this model, the effect of dispersion of solid solution elements during thermal deformation on microstructure evolution was considered, as well as the effects of friction and adiabatic heating on the temperature and strain rate-dependent variation of flow stresses. The hot deformation activation energy of the Ni–W–Cr superalloy was 323 kJ/mol, which was less than that of the Hastelloy N alloy (currently used in MSRs). According to the rectified flow stress data, processing maps were created. In conjunction with the corresponding deformation microstructures, the flow instability domains of the Ni–W–Cr superalloy were determined to be 1050–1160 °C/0.03–1 s⁻¹ and 1170–1200 °C/0.001–0.09 s⁻¹. In these deformation conditions, a locally inhomogeneous microstructure was caused by flow—i.e., incomplete dynamic recrystallization and hot working parameters should avoid sliding into these domains. The ideal processing hot deformation domain for the Ni–W–Cr superalloy was determined to be 1170–1200 °C/0.6–1 s⁻¹.

Zirconium (Zr) emerges as the most effective grain refiner for magnesium (Mg) alloys incorporating Zr. Typically, Zr is introduced in the form of an Mg–Zr master alloy. However, within Mg–Zr master alloys, Zr predominantly exists in a particle form, which tends to aggregate due to attractive van der Waals forces. The clustered Zr is prone to settling, thereby reducing its refining impact on Mg alloys. In this work, a combined pretreatment process for Mg–Zr master alloys was proposed, encompassing the introduction of a physical field to intervene the agglomeration of particle Zr and the employ of high-temperature dissolution and peritectic reactions to promote the solid solution of Zr. The results demonstrate that the particle Zr within the pretreated Mg–Zr master alloy is effectively dispersed and refined, and greater solute Zr levels can be achieved. The subsequent grain refinement ability was studied on a typical Mg–6Zn–0.6Zr (wt%) alloy. The outcome highlights that an improvement in the grain refinement efficacy (32.4%) of Mg–Zr master alloys was obtained with a holding time of 60 min. The pretreated Mg–Zr master alloy significantly augments the efficiency of grain refinement for Mg alloys through a synergistic strategy involving heterogeneous nucleation and solute-driven growth restriction. The crucial factor in achieving effective grain refinement of Zr in Mg alloys lies in regulating the presence and morphology of Zr in the Mg–Zr master alloy, distinguishing between particle Zr and solute Zr. This study introduces a novel method for developing more efficient Mg–Zr refiners.

The Al₂O₃ laminated preforms with different layers thickness were prepared by freezing casting in present work. Then, the Al₂O_3p/AZ91 magnesium matrix laminated materials were obtained by infiltrating the AZ91 alloy melt into the Al₂O₃ laminated preform based on pressure infiltration process. Subsequently, the influence of freezing temperature on the microstructure, mechanical properties and fracture behavior of magnesium-based laminates was investigated. The results indicated that with the decrease of freezing temperature, the thickness of Al₂O₃ layers decreases gradually, the number of layers increases obviously, and the interlayers spacing decreases. Accompanied with the decrease of interlayers spacing, the size of Mg₁₇Al₁₂ phase precipitated in the AZ91 alloy layers was refined, and the compression strength and strain were both improved obviously. The micro-cracks initiated in Al₂O₃ layers during loading process, while the AZ91 layers could effectively suppress the initiation and propagation of micro-cracks. Furthermore, the changing layers structure influenced by the decrease of freezing temperature had significant inhibiting effect on the initiation and propagation of micro-cracks, which endowed the Al₂O_3p/AZ91 magnesium matrix laminated materials with better strength and toughness. Notably, the best compression properties of Al₂O_3p/AZ91 magnesium matrix laminated materials could be obtained at the freezing temperature of − 50 °C, the compression strength and elastic modulus of which were the 160% and 250% of monolithic AZ91 alloy, respectively.

The Zn0.6Cu wires are fabricated into stents for the potential biodegradable application of nasal wound healing. The degradation behavior of Zn0.6Cu stents in 0.9 wt% NaCl at 36.5 °C is evaluated. It shows that the untreated Zn0.6Cu stent experiences severe crevice corrosion with acceleration and autocatalytic effects within the micro-cracks and ruptures at 4.67 ± 1.15 d, with the average corrosion rate of 0.28 mm y⁻¹. Fortunately, the anodic polarization (AP) + hydrothermal (H) conversion coating, consisting of ZnCO₃, Zn(OH)₂ and ZnO, could inhibit the crevice corrosion significantly by reducing the cathode/anode ratio, extending the rupture time up to 16.50 ± 2.95 d, with the average corrosion rate of 0.14 mm y⁻¹. This research indicates that the biodegradable Zn-based stent has some potential applications in nasal wound recovery area.