Journal of Materials Research and Technology-Jmr&t最新文献

Copper-based alloys have garnered significant attention for their potential in antimicrobial applications aimed at mitigating medical-related infections. Nonetheless, the alloying elements in conventional copper alloys frequently exhibit biotoxicity. This study explored the corrosion behavior, antimicrobial activity, and ion release of Cu–Fe alloys with varying iron contents and aging treatment. The results indicate that increasing the iron content in Cu–Fe alloys and applying appropriate aging treatment can enhance both the antibacterial efficiency and corrosion rate. Transmission electron microscopy (TEM) observations revealed a corrosion mechanism in which dispersed iron phases act as nucleation sites. These nanoscale precipitates increase the Cu/Fe interfacial area, thereby promoting ion release at the interface. Furthermore, in-situ scanning electron microscopy (SEM) revealed that corrosion products are more likely to detach in iron-rich segregated areas, which effectively promotes the sustained release of copper ions.

This study investigates the influence of extrusion and deformation temperatures on the mechanical properties of the AZ61 Mg alloy. Increasing the extrusion temperature from 300 to 400 °C led to larger grain size and higher basal texture intensity. At 400 °C, the AZ61 alloy exhibited more Al–Mn phases and fewer Mg₁₇Al₁₂ phases, indicating enhanced dissolution of Mg₁₇Al₁₂ in the α-Mg matrix. Uniaxial tensile tests were conducted at room temperature (RT) and cryogenic temperature (CT, −150 °C). Despite grain growth, a higher yield strength (YS) was achieved at higher extrusion temperatures due to the texture-strengthening mechanism. However, during deformation at CT, the higher YS was primarily attributed to the formation of multiple twinning within individual grains, causing twinning interactions. These twin-interacting boundaries create additional barriers to dislocation movement. Notably, the AZ61 sample extruded at 400 °C demonstrated the formation of stacking faults during deformation at CT, with dislocations accumulating around the faults. This contributed to the best strength without compromising ductility in this sample.

In view of the significant impact of welding defects on the fracture behaviors involving the strength, stress concentration and bearing capacity of welded joint, etc., the propagation behaviors and mechanical properties of welded joints with porosity and micro crack are deeply investigated using a multiscale method. In this work, a crack nucleation and propagation model based on crystal plasticity theory, combined with the extended finite element method (XFEM), is established for the T-welded joint. The maximum slip on the predominant slip system method is applied to predict the crack propagation path of pores and micro cracks in the weld zone (WZ), and the effect of crystal orientation on crack growth is explored. Then, a continuous model is used to analyze the micro and macro fracture behaviors near the weld under tensile load, combined with the maximum principal stress method. The WZ and heat affected zone (HAZ) are observed using electron backscatter diffraction (EBSD) to study the microstructure evolution. Considering grain boundaries, the image information of crystal morphology is processed through binary image analysis for FE modeling. The local mechanical properties testing is carried out using micro-specimens of HAZ and WZ to calibrate the crystal plastic parameters. The results show that the resolved shear stress of the predominant slip system of crack initiation and propagation elements is increased by pore and crack defects. The fracture positions of tensile specimens through numerical simulation are in good agreement with the macroscopic experimental results. It will provide an analysis basis for preventing fracture failure and improving the service performance of thin-walled structures in future.

A carbide strengthened wrought Ni-based superalloy is developed. The alloy depends on carbide dispersion strengthening. A high deformation plasticity in homogeneous alloy is shown in the 1100–1200 °C isothermal compression test and the improvement of microstructure can be achieved by recrystallization. After aging at 850–900 °C, the carbide strengthened wrought alloy appears excellent tensile strength. Carbide exists higher microstructure stability than γ′ in the same condition. The herein reported results reflect the potential of the economical wrought Ni-based superalloy to service above 800 °C.

High-performance titanium alloys with good corrosion resistance are expected to be applied in marine environments. In this work, we developed a Ti20W alloy using powder metallurgy and hot extrusion, which combined remarkable mechanical properties and good corrosion resistance. The Ti20W alloys exhibited ultrahigh strength (>1400 MPa) and good ductility (>7%), and the specific yield strength was comparable to the common high-strength Ti alloys. The ultrahigh-strength Ti20W alloys had characteristics of the solid solution of W atoms and the precipitation of fine α phases. Compared with Ti6Al4V alloy, the Ti20W alloys showed lower corrosion current density values in 3.5 wt% NaCl solution, which was attributed to the solid solution of W elements and the finer α phases. The W oxides, particularly WO₃, acted as the barrier to effectively block the penetration of Cl⁻ into the inner oxide layer, thereby enhancing the corrosion resistance. The fine α phases could be bridged by the surrounding matrix oxides during the passivation process, which contributed to decreasing the galvanic corrosion between the α phases and the matrix, further improving the corrosion resistance.

In this study, the nucleation and growth mechanisms of Al₁₁Ce₃ intermetallic compounds (IMCs) in a hypereutectic Al–Ce alloy during solidification were investigated through synchrotron radiation X-ray real-time imaging. The results showed that Al₁₁Ce₃ IMCs nucleate and grow from the melt as the primary phase at the initial stage of solidification. Growth preferred orientations were observed in two opposite directions, resulting in an I-shaped growth pattern. Based on the minimum energy criterion, the morphology of Al₁₁Ce₃ IMCs displayed either hollow cubic tubes or grooves. The nucleation and growth rates of Al₁₁Ce₃ IMCs gradually decreased over time, owing to the variations in the Ce concentration in the melt and the undercooling. The nucleation and growth characteristics of Al₁₁Ce₃ IMCs can provide the theoretical basis for optimization on the performance of Al–Ce alloys.

Gradient triply periodic minimal surface (TPMS) structures are renowned for lightweight design and enhanced performance, but their complex and nonlinear configurations pose challenges in achieving targeted design goals. A new design methodology for the nonlinear gradient structure was proposed in this study, with the aim of achieving efficient and accurate modeling of complex and gradient sheet-based TPMS structures under specific performance objectives. This method utilized automated finite element (FE) simulations to obtain structure topology element densities under various boundary conditions. An artificial neural network (ANN) was then employed to efficiently predict the correspondence between these boundary conditions and topology element densities. A mapping was established between topology element densities and TPMS structural parameters, and the gradient structure was accurately constructed by using the voxel modeling technique. Taking a typical cantilever beam TPMS structure as an example of nonlinear gradient design, the results indicate that the error between the ANN-predicted and FE-simulated structure topology element densities is only 2.73 %, with prediction time being only 0.15 % of the simulation time. The thin regions of the gradient structure align with those geometrically removed in regular topology optimization scheme, achieving up to 65.45 % weight reduction, a 28.72 % improvement over the regular scheme, along with uniform structural stress transition and maximum stress reduction. TC4 alloy nonlinear gradient TPMS structures, printed by metal selective laser melting (SLM) technique, confirm the practical application value of this design method.

Nano-Y₂O₃-dispersion strengthened CoCrFeNi high entropy alloys are fabricated via mechanical alloying and spark plasma sintering using high purity elemental powders or pre-alloyed CoCrFeNi powder. All the alloys show an FCC matrix incorporated by small amount of BCC Cr-rich segregations, whose brittle nature is detrimental to the mechanical properties of the alloys. It has been found that using pre-alloyed powder significantly suppresses the formation of the Cr-rich phase, and its size and volume fraction can be further reduced by increasing the rotation speed of ball-milling during mechanical alloying. Besides, the grain refinement is also achieved under a higher rotation speed. Y₂O₃ nanoparticles with a number density of 1.8 × 10²² m⁻³ and an average diameter of 11.0 ± 7.3 nm are uniformly distributed in the alloy that produced from pre-alloyed powder under the rotation speed of 350 rpm during ball-milling. These Y₂O₃ nanoparticles share coherent interface with the FCC matrix, indicating the in-situ precipitation mechanism. Due to a good combination of grain boundary strengthening, dislocation strengthening and precipitation strengthening, this ODS high entropy alloy possesses a yield strength of 1281 MPa at room temperature.

Manufacturing maraging steel components using laser-based powder bed fusion (LPBF) presents an attractive proposition for industries due to the material's combination of mechanical properties such as hardness, wear resistance, toughness and the capability to produce parts with complex geometries and high precision. Despite these advantages, the LPBF process induces defects such as distortion and residual stress associated with the complex thermal cycles, compromising final part quality. Numerical simulations have been developed to predict these defects. However, LPBF simulations remain challenging due to the complexity of the process and the substantial computational resources required. For maraging steel, for example, the occurrence of phase transformation promotes compressive stress that interferes in results and makes simulations inaccurate. This research aims to simulate a geometry with a circular inner channel and investigate distortion, volume fraction of martensite and equivalent stress results. Modeling was performed by varying phase transformation rate parameters to assess the impact of transformations on simulation outcomes. Results showed minimal impact of these parameters on distortions and equivalent stress. Equivalent stress results were compared with literature findings, while distortion results were validated against experimental data to validate the accuracy of the model.

Based on the dual enhancement effect of hardening and plasticity in aluminum alloys at cryogenic temperatures, the cryogenic incremental sheet forming process is introduced in this paper for manufacturing complex components. Experimental results indicate that incremental sheet forming at cryogenic environments results in a remarkable enhancement of formability. The ultimate forming height of specimen at 113K presents an increase of 32.4% compared with the specimen at 295K. Meanwhile, it is confirmed that cryogenic conditions increase the work-hardening ability and reduce the microcrack generation on the specimen surface. Moreover, the mechanism of dual enhancement effect on 6061 alloy during cryogenic incremental forming was studied. At 295 K, the dislocation distribution was localized due to significant cross-slip in the specimens. It was also observed that dislocation entanglement occurred at grain boundaries, which tends to cause stress concentration and therefore reduced formability. In contrast, at 113 K, the decrease in stacking fault energy leads to suppression of cross-slip, and the uniform slip leads to a significant increase in dislocation density. As a result, the cryogenic temperature exhibits enhanced work-hardening ability and formability. The rolling texture evolves mainly along the α and β orientation lines during the forming process, the 295K specimen generates a large number of Goss textures in the final forming region due to the uneven deformation which makes it difficult for the texture to evolve further. In contrast, at 113 K the texture fully evolves and intersects in the Brass texture along the two orientation lines due to the enhanced formability.