Yue Zhang

Thin metallic bipolar plates with fine flow channels are prone to nonuniform filling and localized thinning, particularly when high-strength Inconel 718 is formed into complex microchannels. To clarify the spatial deformation characteristics under superplastic conditions, a reduced internal-state-variable-based viscoplastic model was implemented in Abaqus and validated against experimental channel geometry and thickness distributions, with a mean absolute percentage error of 3.63%. The effects of forming temperature, deformation time and initial sheet thickness were evaluated through single-factor simulations and an L9 (3³) orthogonal analysis. Straight-channel nonuniformity was governed mainly by edge-controlled material feeding: increasing temperature or deformation time reduced forming resistance and edge draw-in and improved channel-depth uniformity, but promoted local grain growth. Corner-channel thinning was controlled primarily by geometry-induced strain localization. Longer deformation time effectively reduced maximum thinning, whereas temperature mainly lowered local stress and had limited influence on thickness loss. Increasing sheet thickness reduced corner thinning up to about 0.14 mm, beyond which the benefit became limited. Orthogonal analysis showed that deformation time dominated global and straight-channel responses, while sheet thickness dominated local corner thinning. The results reveal two governing regimes-rate-dependent flow with edge feeding for straight channels, and geometric localization with thickness reserve for corner channels, providing a mechanistic basis for process design of Inconel 718 bipolar plates.

5383 Al-Mg alloy is widely used in marine structures owing to its low density, high specific strength, good formability, and excellent corrosion resistance. However, its relatively high Mg content makes it susceptible to β-phase (Al₃Mg₂) precipitation at grain boundaries, which deteriorates both mechanical performance and corrosion resistance. In this work, the synergistic effects of cold rolling and stabilizing heat treatment (SHT) on the microstructure evolution, mechanical properties, and corrosion behavior of 5383 Al alloy were systematically investigated, with particular emphasis on the microstructural origin of the strength-corrosion trade-off. The results show that increasing the rolling reduction from 14% to 22.8% significantly improves the ultimate tensile strength from 377 MPa to 403 MPa, which is associated with grain elongation, a higher fraction of low-angle grain boundaries, and a more homogeneous distribution of the Al-Mn phase. Subsequent SHT at 180-250 °C slightly decreases the tensile strength with increasing temperature, but markedly improves corrosion resistance. In particular, β-phase precipitation is evident after SHT at 220 °C, whereas it is effectively redissolved at 250 °C, leading to a substantial reduction in intergranular corrosion depth to below 100 μm. The results demonstrate that the synergy between deformation-induced boundary structure evolution and temperature-dependent phase regulation enables an improved balance between strength and corrosion resistance. This study provides new insight into microstructure-mediated property optimization in high-Mg Al alloys and offers practical guidance for the processing design of corrosion-resistant marine aluminum alloys.

Additive manufacturing of magnesium rare-earth (Mg-RE) alloys has drawn much attention due to the outstanding specific strength of the alloys and the unique feature of additive manufacturing method, which becomes a great potential manufacturing method of complex structural component in aerospace industry. Some efforts have been devoted to the microstructural evolution and the room temperature mechanical properties, neglecting the mechanical properties at high-temperature especially for the Mg-RE alloy with high RE contents. Hence we performed cold metal transfer wire arc additive manufacturing (CMT-WAAM) on a Mg-8Gd-3Y-0.3Zn-0.3Zr (GW83Z) alloy, and the influence of subsequent heat treatment on the microstructure evolution and elevated-temperature stability of the WAAM Mg-RE alloy was evaluated. The results show that the as-WAAM alloy exhibited a fine-grained structure with an average grain size of ~21.5 μm. Coarse eutectic phases segregated on grain boundaries which deteriorated the mechanical properties. Fine strip shaped γ′ phase and preliminary long-period stacking ordered (LPSO) phase with 18R structure could be observed. The hardness of the as-WAAM sample was ~90 HV, and the ultimate tensile strength (UTS) reached 262 MPa, with little anisotropy for the horizontal and vertical directions. After the optimized heat treatment (solid solution at 500 °C for 12 h followed by aging at 200 °C for 30 h), the UTS significantly increased to 338 MPa. More importantly, almost lossless UTS of 326 MPa was achieved at a high temperature of 200 °C due to the formation of thermally stable 14H-LPSO phase and nano-scale β′ precipitates.

Microalloying aluminum alloys have exhibited excellent conductivity and ductility, which can meet the increasing requirements of applications in high‐speed train electric equipment as well as the goals for energy conservation. However, the low tensile strength, because of the lack of precipitation, has limited these potential applications of microalloying aluminum alloy. The present work has proposed microalloying of the rare earth Er element in an Al‐based alloy combining homogenization annealing treatment to break the disproportionate match between tensile property and electrical conductivity of the alloys. The results demonstrate that microalloying with the Er element inhibits the intrinsic growth of α‐Al, promoting a significant grain refinement of the alloy. Besides, the shape of Al₁₃Fe₄ particles has also been modified. The subsequent homogenization annealing treatment at 550 °C for 1 h has resulted in a synergistic increase of the tensile property and electrical conductivity in the Al–0.7Fe–0.4 Mg–0.1Si–0.5Er alloy, where the ultimate tensile strength has reached 114 MPa, the elongation to failure has remained 28.2%, and the electrical conductivity has regained 58.8 %IACS. Based on the yield strength expression calculation, the emergence of the Al₃Er phase primarily contributes to the strengthening of the 0.5 wt% Er alloy.

The NiCr–TiB₂–ZrB₂ composite coating was deposited on the surface of blades made of steel (SUS304) using high-energy ball milling technology and air plasma spraying technology, which aimed to relieve the wear of the blades during operation. The influence of titanium diboride (TiB₂) and zirconium diboride (ZrB₂) on the microstructure and wear resistance of the coatings was investigated by X-ray diffraction, scanning electron microscopy, Vickers microhardness tester, and a wear tester. The results showed that the TiB₂ and ZrB₂ particles were unevenly distributed in the coatings and significantly increased the hardness and anti-wear, which contributed to their ultra-high hardness and extremely strong ability to resist deformation. The performance of the coatings was improved with the increase of the number of ceramic phases, while the hardness and wear resistance of the coating could reach their highest value when the TiB₂ and ZrB₂ respectively took up 15 wt.% of the total mass of the powder.

Nickel chromium (NiCr) powders with different titanium diboride (TiB₂) additions (20, 40 and 60 wt %) were prepared with a mechanical alloying method and then sprayed using an air plasma spraying technology. The microstructure and phase composite of the powders and the cross-sections of deposited coatings were analyzed with a scanning electronic microscope and X-ray diffraction. The tribological performance of the coatings was studied using a pin-on-disk tribometer at room temperature. The weight loss of the as-sprayed coating was measured by using a high accuracy weighing balance. Cr₃C₂-25NiCr coating was produced and tested for comparison. The morphologies of the worn surface were then investigated. Parts of debris with some scratches were found, presenting typical signs of abrasive wear and showing slight adhesive wear on the surface. The 20 wt % additive TiB₂ coating demonstrated the highest microhardness and the lowest coefficient of friction. The wear resistance of the metal-ceramic composites coatings was enhanced with the addition of TiB₂.

This work investigates the mechanisms of the microstructure evolution in the melted surface layers of a WC-6% Co hard alloy when increasing the number of pulses of irradiation by high-current pulsed electron beam (HCPEB) treatment. After one pulse of irradiation, about 50% of the stable hcp WC phase was melted and resolidified into the metastable fcc form (WC_1−x). When increasing the numbers of pulse irradiation, the WC phase decomposed into ultrafine-grained WC_1−x plus nanosized graphite under our selected energy condition. Because of the rapidity of HCPEB carried under vacuum, the formation of the brittle W₂C phase was avoided. In the initial Co-rich areas, where the Co was evaporated, melting and solidification led to the formation of nanostructures Co₃W₉C₄ and Co₃W₃C. The volume fraction of the nano domains containing WC_1−x, Co₃W₉C₄, and Co₃W₃C phases reached its maximum after 20 pulses of irradiation. The improved properties after 20 pulses are therefore due to the presence of nano graphite that served as lubricant and dramatically decreased the friction coefficient, while the ultrafine-grained carbides and the nano domains contribute to the improvement of the surface microhardness and wear resistance.

High-entropy alloys (HEAs) are emerging as a hot research frontier in the metallic materials field. The study on the effect of alloying elements on the structure and properties of HEAs may contribute to the progress of the research and accelerate the application in actual production. FeCoCrNiAlTi_x (x = 0, 0.25, 0.5, 0.75, and 1 in at.%, respectively) HEA coatings with different Ti concentrations were produced on Q235 steel via laser cladding. The constituent phases, microstructure, hardness, and wear resistance of the coatings were investigated by XRD, SEM, microhardness tester and friction-wear tester, respectively. The results show that the structure of the coating is a eutectic microstructure of FCC and BCC₁ at x = 0. The structure of coatings consists of both proeutectic FCC phase and the eutectic structure of BCC₁ and BCC₂. With the continuous addition of Ti, the amount of eutectic structure decreases. The average hardness of the FeCoCrNiAlTi_x HEA coatings at x = 0, 0.25, 0.5, 0.75, and 1 are 432.73 HV, 548.81 HV, 651.03 HV, 769.20 HV, and 966.29 HV, respectively. The hardness of coatings increases with the addition of Ti, where the maximum hardness is achieved for the HEA at x = 1. The wear resistance of the HEA coatings is enhanced with the addition of Ti, and the main worn mechanism is abrasive wear.