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Metal lattice structural materials are widely used in aerospace, automotive industry, and other fields due to their advantages of lightweight, high specific strength, energy absorption, and porosity. High strength and toughness FeCrNi medium entropy alloy (MEA) was taken as the research object, and selective laser melting (SLM) was used to prepare FeCrNi medium entropy alloy lattice structure materials with four simulated lattice structures: BCC, BCCZ, FCC and FCC. The microstructure, mechanical properties, and deformation behavior of these materials were systematically studied.The results indicate that the FeCrNi medium entropy alloy lattice structure prepared by the skip scanning strategy has high node overlap quality, dense interlaced stacking of molten pools, and uniform and fine grains. When the relative density is similar, the specific strength and specific energy absorption values of BCC, FCC, BCCZ, and FCCZ lattice structures increase sequentially.The specific energy absorption of FeCrNi medium entropy alloy material with FCCZ lattice structure reaches 49.8J·g-1, significantly higher than that of Ti6Al4V and 316L stainless steel lattice materials.The finite element simulation analysis shows that the presence of Z-shaped pillars increases the apparent strength and stiffness of the lattice material, and leads to a transition in deformation behavior from bending dominated to tensile dominated, which is the main reason for the strength improvement of the FCCZ lattice structure.

The Nb-16Si-24Ti-2Al-2Cr alloy was prepared by plasma rotating electrode process (PREP) technology and the hot-pressing (HP) method, and the effects of sintering temperature on the microstructure, mechanical properties and fracture behavior were investigated. The HP alloys sintered at temperatures below 1400 °C are composed of Nbss (Nb solid solution), Nb3Si and Nb5Si3 phases. When the sintering temperature reaches 1450 °C, the Nb3Si phase is completely decomposed into Nbss and Nb5Si3 phases. Meanwhile, the microstructure coarsens significantly. Compared with the cast alloy, the HP alloy shows better mechanical properties. The fracture toughness of the alloy sintered at 1400 °C reaches 20.2 MPa·m1/2, which exceeds the application threshold. The main reason for the highest fracture toughness is attributed to the decomposition of large-sized brittle Nb3Si phase and the formation of a fine microstructure, which greatly increases the number of phase interfaces and improves the chance of crack deflection. In addition, the reduction in the size and content of silicides also reduces their plastic constraints on the ductile Nbss phase. [ABSTRACT FROM AUTHOR]

Graphene/copper composites are promising in electronic and energy fields due to their superior conductivity, but microstructure control during thermal mechanical processing (TMP) remains a crucial issue for the manufacturing of high-performance graphene/copper composites. In this study, the hot deformation behavior of graphene/copper composites was investigated by isothermal compression tests at deformation temperatures of 700~850 °C and strain rates of 0.01~10 s−1, and a constitutive equation based on the Arrhenius model and hot processing map was established. Results demonstrate that the deformation mechanism of the graphene/copper composites mainly involves dynamic recrystallization (DRX), and such DRX-mediated deformation behavior can be accurately described by the established Arrhenius model. In addition, it was found that the strain rate has a stronger impact on the DRX grain size than the deformation temperature. The optimum deformation temperature and strain rate were determined to be 800 °C and 1 s−1, respectively, with which a uniform microstructure with fine grains can be obtained. [ABSTRACT FROM AUTHOR]

Nickel‐based alloys exhibit excellent mechanical properties, but the corrosion resistance when exposed to NaCl solution needs to be improved, thus limiting their widespread applications. In this study, it is demonstrated that a moderate addition of boron, specifically 3.5 wt%, can effectively enhance both the tribological properties and corrosion resistance of Ni‐based alloys. The microstructures evolution and corrosion mechanism of Ni–Cu–xB (0–5 wt%) alloys have been comprehensively investigated through the experimental characterization and phase diagram calculations. The improvements in corrosion resistance can be primarily attributed to the formation of continuous and dense passivation films. Additionally, the dissolved B fixes chloride ions to hinder the breakdown of passivation films. However, an excessive addition of boron can have a detrimental effect on corrosion resistance. While improving the formation of dense passivation films, the excessive presence of boron also prompts the precipitation of a Cu‐rich phase that is highly susceptible to corrosion by chloride ions, thereby exacerbating the corrosion process in the alloy. [ABSTRACT FROM AUTHOR]

The aims of this retrospective study were to evaluate the clinical applicability of the latest International Society for the Study of Vulvovaginal Disease (ISSVD) and International Federation for Cervical Pathology and Colposcopy (IFCPC) terminology for vulvar diseases, and to explore a new evaluation flow to optimize decision-making on diagnosis. A total of 1,068 patients with 5,340 qualified vulvar images were evaluated by observers using 2011 ISSVD and 2011 IFCPC terminology systems. The sensitivity, specificity, positive predictive value, negative predictive value, Youden Index and Overall Diagnostic Value (ODV) were calculated for each finding in the two systems. Then the disease diagnosis order and a diagnosis flow draft (DFD) were obtained. A total of 15 kinds of vulvar diseases were diagnosed. The proportion of patients accompanied with cervical or vaginal intraepithelial neoplasia was highest (83.3 %) in vulvar Paget's disease group (p<0.001). Total area of lesions was larger in vulvar Paget's disease, lichen simplex chronicus and lichen sclerosus group (p<0.001). Among the top five findings of ODV, some findings inferred several (≥6) kinds of diseases, while some findings only exist in a certain disease. When the DFD was used, the agreement between the initial impression and histopathology diagnosis was 68.8 %, higher than those when ISSVD an IFCPC terminology systems used (p=0.028), and it didn't change with the experience of the observer (p=0.178). Based on the findings in ISSVD and IFCPC terminology systems, we explored a DFD for observers with different experience on the detection of vulvar disease. [ABSTRACT FROM AUTHOR]

FeCrNi medium entropy alloy (MEA) has been widely regarded for its excellent mechanical properties and corrosion resistance. However, insufficient strength limits its industrial application. Intermetallic particle dispersion strengthening is considered to be an effective method to improve strength, which is expected to solve this problem. In this work, microstructural evolution and mechanical behavior of FeCrNi MEA with different Si content were investigated. We found that the precipitation of fine σ particles can be formed in situ by thermomechanical treatment of Si doping FeCrNi MEAs. The FeCrNiSi0.15 MEA exhibits a good combination of strength and ductility, with yield strength and tensile elongation of 1050 MPa and 7.84%, respectively. The yield strength is almost five times that of the as-cast FeCrNi MEA. The strength enhancement is mainly attributed to the grain-boundary strengthening and precipitation strengthening caused by fine σ particles. [ABSTRACT FROM AUTHOR]

FeCrNi medium entropy alloy (MEA) is a promising structural material due to its outstanding mechanical properties and corrosion resistance. However, study on the high-temperature tribological behaviors of FeCrNi MEA is still scarce. This work investigates the tribological performances of the FeCrNi MEA against Si3N4 balls over typical operating temperatures from 25 to 800 °C. The FeCrNi MEA exhibits excellent wear resistance at an intermediate temperature of 600 °C. The microstructure characterization of the wear tracks reveals a transition in the wear mechanism from abrasive wear at 25 °C to oxidative-delamination wear at 600 °C. The improved tribological performances are mainly attributed to the high Cr content, which promotes the formation of the compact oxide layer and the precipitation of the hard sigma (σ) phase. [ABSTRACT FROM AUTHOR]

High-activity spherical TaNbTiZr refractory high-entropy alloy (REHA) powders were successfully prepared by electrode induction melting gas atomization (EIGA) and plasma rotating electrode process (PREP) methods. Both the EIGAed and PREPed TaNbTiZr RHEA powders have a single-phase body-centered cubic (BCC) structure and low oxygen content. Compared with the EIGAed powders, the PREPed powders exhibit higher sphericity and smoother surface, but larger particle size. The average particle sizes of the EIGAed and PREPed powders are 51.8 and 65.9 μm, respectively. In addition, both the coarse EIGAed and PREPed powders have dendritic structure, and the dendrite size of the EIGAed powders is larger than that of the PREPed powders. Theoretical calculation indicates that the cooling rate of the PREPed powders is one order of magnitude higher than that of the EIGAed powders during the solidification process, and the dendritic structure has more time to grow during EIGA, which is the main reason for the coarser dendrite size of the EIGAed powders. [ABSTRACT FROM AUTHOR]