Chao Lu

Improving the strength of Al conductive alloys while maintaining high electrical conductivity (EC) remains a long-standing challenge, as conventional strengthening strategies usually degrade electrical performance. Although multi-element microalloying has been explored for Al-Si alloys in the prior literature, most existing studies fail to achieve the simultaneous refinement of eutectic Si and controlled precipitation of multi-scale nanoprecipitates, often leading to a strength–conductivity trade-off. In this work, a novel Al-4Si-1.1Mg-0.13Zr-0.06Cu-0.15Sc conductive alloy was designed, integrating trace Mg/Zr/Cu/Sc microalloying with hot extrusion and tailored heat treatment. The results reveal that the individual addition of these alloying elements greatly raises alloy hardness but inevitably reduces EC. The combined hot extrusion and heat treatment solves this dilemma: eutectic Si particles are refined to ~200 nm with a uniform distribution, while nano-sized Mg₂Si (~15 nm) and Al₄Zr(Sc)₃Si₅ (~50 nm) precipitates are formed. The synergistic strengthening of these multi-scale precipitates enables prominent mechanical enhancement without sacrificing electrical conductivity, which distinguishes this work from many previous Al-Si alloy reports. After the optimized two-step heat treatment (500 °C/4 h + 200 °C/48 h), the alloy achieves excellent comprehensive performance: yield strength of 164.0 MPa, ultimate tensile strength of 364.0 MPa, hardness of 106.0 HV, elongation of 9.0%, and EC of 50.8% IACS. This work provides a feasible microstructure engineering strategy for designing high-performance conductive aluminum alloys by precise multi-component composition control.

Laser melting deposition (LMD) was employed to fabricate 5.0 wt.% TiC-reinforced 316L composite coatings, and the role of laser power in governing microstructure evolution and performance was systematically investigated. Particular emphasis was placed on the laser-power-dependent evolution mechanism of TiC, covering the coexistence of retained undissolved TiC and fine reprecipitated nanoscale TiC phases; critically, this work clarifies their combined regulating effects on hardness, wear, and corrosion behavior, advancing the understanding of structure-property correlation for LMD 316L/TiC composites. The results show that increasing laser power markedly altered melt-pool dynamics, particle dissolution, and interfacial heterogeneity, thereby regulating the process–microstructure–property relationship of the coatings. Owing to the synergistic effects of residual TiC reinforcement, fine-particle dispersion, and microstructural refinement, the P14 and P16 coatings exhibited the highest hardness, reaching ~320–330 HV. However, the best wear resistance was achieved at moderate laser power, indicating that excessive hardening did not necessarily lead to optimal tribological performance because of increased local heterogeneity and particle detachment tendency. Electrochemical results further revealed that corrosion resistance was jointly controlled by passive-film stability and particle/matrix interfacial activation. Among all samples, P12 showed the most favorable overall corrosion performance, reflecting an optimized balance between microstructural uniformity and interfacial stability. These findings demonstrate that appropriate laser power is critical for simultaneously optimizing strengthening and corrosion resistance in the LMD-fabricated 316L/TiC composite.

Aluminum–silicon (Al-Si) alloys are widely used in aerospace, automotive manufacturing, power electronics, marine engineering and other fields due to their excellent physical properties. However, their corrosion resistance is insufficient in harsh service environments. In this study, a variety of characterization methods were adopted, including scanning electron microscopy (SEM), X-ray diffraction (XRD), electrochemical measurements (electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization), immersion corrosion tests, and scanning vibrating electrode technique (SVET). The results show that the appropriate heat treatment regime can significantly enhance the corrosion resistance of the alloy, while improper aging parameters will aggravate the corrosion tendency. The optimal heat treatment regime is solution treatment at 500 °C for 4 h followed by aging at 200 °C for 48 h. Under this condition, the corrosion current density (i_corr) is as low as 79.30 μA/cm², and the low-frequency impedance modulus and phase angle in EIS tests are optimal. The as-extruded alloy exhibits severe localized corrosion, while the heat-treated alloy transforms into mild and uniform corrosion. The underlying mechanism is that heat treatment induces the formation of uniformly distributed nanoscale Mg₂Si and Al₃(Sc,Zr) precipitates, which synergistically improve the corrosion resistance of the alloy by weakening micro-galvanic coupling and facilitating the formation of a stable passive film.

Oxide dispersion-strengthened (ODS) alloys are regarded as one of the most promising materials for Generation IV nuclear fission systems, owing to their exceptional attributes such as high strength, corrosion resistance, and irradiation tolerance. The traditional methods for fabricating oxide dispersion-strengthened (ODS) alloys are both time-consuming and costly. In contrast, additive manufacturing (AM) technologies enable precise control over material composition and geometric structure at the nanoscale, thereby enhancing the mechanical properties of components while reducing their weight. This novel approach offers significant advantages over conventional techniques, including reduced production costs, improved manufacturing efficiency, and more uniform distribution of oxide nanoparticles. This review begins by summarizing the state of the art in Fe-based and Ni-based ODS alloys fabricated via traditional routes. Subsequently, it examines recent progress in the AM of ODS alloys, including Fe-based, Ni-based, high-entropy alloys, and medium-entropy alloys, using powder bed fusion (PBF), directed energy deposition (DED), and wire arc additive manufacturing (WAAM). The microstructural characteristics, including oxide particle distribution, grain morphology, and alloy properties, are discussed in the context of different AM processes. Finally, critical challenges and future research directions for laser-based AM of ODS alloys are highlighted.

In this study, a new kind of the Al-1Si-0.6Mg-0.2Fe alloy was fabricated by Mg, Fe alloying treatment and the influence mechanism of Mg, Fe on electrical conductivity (EC) and Vickers hardness (HV) of the Al-1Si alloy was analyzed by the combination of experiments and simulations. Results showed that during the solidification process, intermediate phase Al₈FeMg₃Si₆ formed which can inhibit the growth of needle-like AlFeSi phase, resulting in a more refined distribution of AlFeSi particles and this is helpful to improve EC and HV simultaneously. According to the simulation results, Al-1Si-0.6Mg-0.2Fe generated the most Al₈FeMg₃Si₆ and the corresponding EC and HV reached 48.5% IACS and 62.9 HV, respectively. Furthermore, during heat treatment process, AlFeSi can promote the nucleation of Mg₂Si, reducing the elemental solution of Mg and Si. With 550 °C/2 h + 210 °C/24 h heat treatment, on the one hand, oversized needle-shaped AlFeSi fused to smaller particles and distributed more uniformly. On the other hand, more solid solution Si and Mg precipitated with form of Mg₂Si. Finally, the EC and HV of Al-1Si-0.6Mg-0.2Fe improved to 54.5% IACS and 79.8 HV, achieving the simultaneous optimization of EC and HV. This can provide theoretical guidance for the preparation of high strength and high conductivity aluminum alloy.

The development of oscillating laser beam welding (OLBW) provides an opportunity to improve the weld formation of dissimilar stainless steels. In this paper, the influence of oscillating amplitude on the weld formation, microstructure, and mechanical properties of dissimilar 430/5Cr15MoV stainless steel was studied. The results showed that the weld morphology became smooth and uniform with an increase in the oscillating amplitude, and there was no obvious defect on the surface. The formation mechanism of weld overflow defects on the weld surface was discussed. The width of the weld metal increased with an increase in oscillation amplitude. The influence of beam oscillation on the microstructure of the weld center was significant, i.e., the proportion of equiaxed grains in the center of the welds increased as the oscillation amplitude increased. The maximum microhardness of the weld was obtained at an amplitude of 1.5 mm. Moreover, the tensile strength of the welds reached 477 MPa, which was comparable to the tensile strength of the 430 stainless steel base material. The fracture modes of all welds were typical ductile fractures, which suggests that the oscillation amplitude had a minor effect on the fracture mechanism of the welds. This study provided a new approach to welding dissimilar stainless steels and offers guidance for the selection of an optimum oscillation amplitude.

This study systematically investigates the influence of the composite addition of Ce, La, and Ca elements on the microstructure evolution and mechanical properties of Mg-3Zn-1Mn/Sn (wt.%) alloys. It indicates that the strength of Mg-Zn-Mn series alloys is superior to that of Mg-Zn-Sn series alloys, due to the stronger restriction of nanosized Mn particles on the recrystallization process and grain growth compared with Mg₂Sn phases. The addition of the Ca-La-Ce elements significantly enhances the strength of the Mg-3Zn-1Sn alloy (YS increased by approximately 92.5%, UTS increased by approximately 29.2%, and EL decreased by nearly 52.2%), while for the Mg-3Zn-1Mn alloy, a balanced effect on both the strength and performance can be achieved. This difference mainly lies in the more pronounced refined effect on the grain size and the formation of a bimodal grain structure with strip-like un-DRXed grains and surrounding fine DRXed grains for the Mg-3Zn-1Sn alloy. In contrast, the addition of the Ca-La-Ce elements has a less obvious hindrance on the recrystallization process in the Mg-Zn-Mn series alloy, while significantly weakening the extrusion texture while refining the grains. Through in-depth characterization and experimental analysis, it is found that Sn and Ca can promote the formation of brittle and fine secondary phases. A nanoscale Sn phase (Mg₂Sn phase) is more likely to accumulate at the grain boundaries, and the size of the nanoscale Ca₂Mg₆Zn₃ in Mg-Zn-Mn series alloys is finer and more dispersed than that in Mg-Zn-Sn series alloys, thus strongly hindering recrystallization and refining the recrystallized structure of the alloy.

Laser cladding technology is a surface modification technology emerging in recent years, and it is widely used in the marine engineering field. Since the structural steels used in marine engineering are mostly carbon steels, their wear resistance and corrosion resistance are poor. In this paper, 316 L stainless steel/TiC composite coatings with different Y₂O₃ addition amounts were fabricated on Q355B steel surface using the laser cladding technology, and the phase composition, microstructure, microhardness, wear resistance, and corrosion resistance of the coatings were investigated with an X-ray diffractometer (XRD), a scanning electron microscope (SEM), a digital microhardness tester, a friction and wear tester, and an electrochemical workstation. When Y₂O₃ is added, the crystals in the bottom part of the coating are basically broken and the organisation becomes more dense. When the Y₂O₃ addition amount is 2%, the hardness is highest, the frictional coefficient curve of the coating exhibits a stable descending trend, and the coating mass loss is the lowest. When Y₂O₃ is added at 1%, the dynamic potential polarisation curve shows high corrosion potential and low corrosion current density and exhibited the best performance in EIS. The added Y₂O₃ evidently improves the wear resistance and corrosion resistance of 316 L stainless steel/TiC composite coatings, and this provides a new possibility that a composite coating modified with rare earth oxide is used for repair of marine engineering structures.