Acta Metallurgica Sinica-English Letters最新文献

Magnesium (Mg) alloy is considered as a promising biodegradable implant material but restricted to rapid degradation. Here, the new strategies based on thixomolding process had been explored to utilize the outstanding anti-permeability of graphene nanosheets (GNPs) while inhibit its galvanic corrosion with the matrix, so as to improve the corrosion resistance of composites. The agglomerate of GNPs with 0.9 wt% content is the main reason for the deterioration of corrosion performance due to the formation of micro-galvanic corrosion. The grain refinement of composites with 0.6 wt% content had positive effects on the better corrosion resistance. After process adjusting, the unique distributions of GNPs along grain boundaries play a vital role in improving the corrosion resistance. It can be ascribed to the following mechanisms: (I) The barriers can be established between the Mg matrix and corrosive medium, hence blocking the charge transfer at the interface; (II) The GNPs can effectively promote apatite deposition on the Mg matrix, leading to form dense apatite layers and prevent the further invasion of SBF; (III) The GNPs acting as reinforcements exists in the corrosion layer and apatite layer, impede the apatite layer falling off from the Mg matrix. These findings broaden the horizon for biomedical applications in Mg matrix composites to realize desired performances.

The Mg–Zn–Gd alloy with quasicrystal icosahedral phase was processed by high-pressure torsion (HPT). The effect of bimodal I-phase on the dynamic recrystallization was analyzed by transmission electron microscopy. The results showed that the block I-phase can stimulate obvious particle-stimulated nucleation and dynamic recrystallization (DRX) grains were preferentially formed after HPT for 5 turns, while the granular I-phase only promoted the generation of sub-grains. The orientation relationship was determined as twofold//[12(overline{1 })0] and fivefold//(0002)_Mg. Moreover, after HPT for 9 turns, the DRX grains induced by block I-phase appeared to grow up and coarsened. Compared with block I-phase, the grains induced by granular I-phase presented much smaller size and distributed more homogeneous due to the strong pinning effect.

Discontinuously reinforced titanium matrix composites (DRTMCs) with a network structure have been extensively researched due to their superior combination of strength and ductility. However, their fatigue performance has remained unknown. In order to elucidate the fatigue behavior of DRTMCs, a tension–tension fatigue test was performed on a TiB/near α-Ti composite with network structure. The results showed that the variability of fatigue lifetime increased as the stress level decreased. Fractography analysis indicated that fatigue crack initiation was associated with facet formation, while the subsequent propagation was hindered by the network structure comprising TiB whiskers and silicides. Crystallographic characterization further revealed that facets formed due to a combination of shear and normal stress. The reduction in fatigue lifetime was attributed to an increase in the effective slip length, which was influenced by the orientation of grains near the crack-initiation sites toward basal slip in the life-limiting specimen. Quasi in situ observation suggested that the crack initiation was facilitated by both basal and prismatic slip of α-Ti as well as fracture of TiBw. Crack propagation was found to be associated with basal and prismatic slip systems with high Schmid factors, regardless of whether the crack was intergranular or intragranular.

SiC is the most common reinforcement in magnesium matrix composites, and the tensile strength of SiC-reinforced magnesium matrix composites is closely related to the distribution of SiC. Achieving a uniform distribution of SiC requires fine control over the parameters of SiC and the processing and preparation process. However, due to the numerous adjustable parameters, using traditional experimental methods requires a considerable amount of experimentation to obtain a uniformly distributed composite material. Therefore, this study adopts a machine learning approach to explore the tensile strength of SiC-reinforced magnesium matrix composites in the mechanical stirring casting process. By analyzing the influence of SiC parameters and processing parameters on composite material performance, we have established an effective predictive model. Furthermore, six different machine learning regression models have been developed to predict the tensile strength of SiC-reinforced magnesium matrix composites. Through validation and comparison, our models demonstrate good accuracy and reliability in predicting the tensile strength of the composite material. The research findings indicate that hot extrusion treatment, SiC content, and stirring time have a significant impact on the tensile strength.

Rapid advancements in the aerospace industry necessitate the development of unified, lightweight and thermally conductive structures. Integrating complex geometries, including bionic and porous structures, is paramount in thermally conductive structures to attain improved thermal conductivity. The design of two high-porosity porous lattice structures was inspired by pomelo peel structure, using Voronoi parametric design. By combining characteristic elements of two high-porostructuressity porous lattice structures designed, a novel high-porosity porous gradient structure is created. This structure is based on gradient design. Utilizing selective laser melting (SLM), fabrication comprises three . Steady-state thermal characteristics are evaluated via finite element analysis (FEA). The experimental thermal conductivity measurements correlate well with simulation results, validating the sequence of K_L as the highest, followed by D_K_L and then D_L. Heat treatment significantly improves thermal conductivity, enhancing the base material by about 45.6% and porous structured samples by approximately 43.7%.

Laser powder bed fusion (LPBF) is a commonly used additive manufacturing (AM) method for efficiently producing intricate geometric components. This investigation examines factors such as pores, cellular structure, grain size, and inclusions from the manufacturing process that contribute to the corrosion resistance of LPBF DSS. Furthermore, the as-built LPBF duplex stainless steel (DSS) is primarily ferrite due to the rapid cooling process. Therefore, the transformation of ferrite to austenite after various heat treatments in LPBF DSS and its corresponding corrosion resistance are presented. Additionally, a new mixed powder method is proposed to increase the austenite content in the as-built LPBF DSS. This review also focuses on the passivation capability and pitting corrosion performance in LPBF and conventional DSS. This article summarizes the variations in microstructure between as-built and heat-treated LPBF DSS, with their impacts on corrosion resistance, offering insights for manufacturing highly corrosion-resistant LPBF DSS.

This research studies the effect of Mn–Co–La₂O₃ coating synthesized by the electrodeposition method on the oxidation resistance and electrical conductivity of the Crofer 22 APU stainless steel interconnect plates in solid oxide fuel cells. The test samples were characterized by a field emission scanning electron microscope (FESEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). The oxidation kinetics of the coated and uncoated samples were studied by tracking their weight changes over time at 800 °C, showing that the oxidation mechanism for all samples follows the parabolic law. Lower oxidation rate constant (k_p) values of the coated sample compared with that of the uncoated one indicated a reduction in the oxidation rate of the steel substrate in the presence of the Mn–Co–La₂O₃ coating. The examination of the cross-section of different samples after the isothermal oxidation for 500 h at 800 °C exhibited that applying the composite coating leads to a decrease in the thickness of the chromia layer formed on the steel surface. Furthermore, under these conditions, the area-specific resistance (ASR) of the coated sample (13.11 mΩ cm²) is significantly lower than that of the uncoated one (41.45 mΩ cm²).

The MCrAlY coating has been potential candidate for the parts applied in friction and corrosion conditions, and CNTs (carbon nanotubes) are expected to improve the service performance of coatings owing to high lubrication and low chemical reactivity. In this work, a systematic investigation on the tribological and corrosion properties of CoCrAlYTaSiC-xCNTs coatings deposited by laser melting was analyzed. Results showed that the coatings had good-quality without typical metallurgical defects. The CNTs addition homogenized and refined the microstructure of coating, and also improved the tribological and corrosion properties. As the CNTs content changed from 0 to 4 wt%, the wear rate of coating decreased from 16.23 × 10^–3 to 7.58 × 10^–3 mg m⁻¹, the j_corr of coating decreased from 4.13 × 10^–4 to 1.23 × 10^–4 A cm⁻², and the R_ct values increased from 12.69 to 25.07 Ω cm².

Improving the shape memory effect and superelasticity of Cu-based shape memory alloys (SMAs) has always been a research hotspot in many countries. This work systematically investigates the effects of Gyroid triply periodic minimal surface (TPMS) lattice structures with different unit sizes and volume fractions on the manufacturing viability, compressive mechanical response, superelasticity and heating recovery properties of CuAlMn SMAs. The results show that the increased specific surface area of the lattice structure leads to increased powder adhesion, making the manufacturability proportional to the unit size and volume fraction. The compressive response of the CuAlMn SMAs Gyroid TPMS lattice structure is negatively correlated with the unit size and positively correlated with the volume fraction. The superelastic recovery of all CuAlMn SMAs with Gyroid TPMS lattice structures is within 5% when the cyclic cumulative strain is set to be 10%. The lattice structure shows the maximum superelasticity when the unit size is 3.00 mm and the volume fraction is 12%, and after heating recovery, the total recovery strain increases as the volume fraction increases. This study introduces a new strategy to enhance the superelastic properties and expand the applications of CuAlMn SMAs in soft robotics, medical equipment, aerospace and other fields.