This paper investigated and experimentally analyzed the penetration behavior of liquid copper along austenite grain boundaries (GBs) at high temperatures. The microstructure of the liquid copper channel network along GBs and triple junctions (TJs), as well as the TJ wetting, was observed and interpreted through diffusion-controlled premelted GB formation. The concentration distribution results along GBs show that copper diffusion in both the near-surface premelted GBs and the non-surface-layer solid-state GBs conform to the diffusion equation, though the diffusion coefficients differ by approximately one order of magnitude. However, the copper concentration at premelted GBs cannot be fully described by an error solution. Using a modified diffusion equation when considering the concentration dependence of the GB diffusion coefficient provides a more accurate description, aligning better with experimental characteristics. Electron backscatter diffraction measurements indicate that the copper orientation at premelted GBs remains consistent with that of surface copper coating, whereas that at solid-state GBs undergoes significant changes. This finding is consistent with the argument that the corresponding material states at premelted GBs are different from those at solid-state GBs, thus providing experimental evidence for the diffusion equation solutions presented above. It provides a theoretical reference for understanding and preventing liquid metal embrittlement.

Strong corrosive atmospheric environments of level C4–C5 have a serious safety impact on steel structures and industrial production. The use of anti-corrosion coatings is the most economical and efficient way of all means of anti-corrosion. To further improve the anticorrosion performance of polyurethane anticorrosion coatings, this paper adopts KH-560 silane coupling agent to modify basalt flake and add it as filler into one-component polyurethane resin with wet curing characteristics. Anti-corrosion coatings were prepared by combining pre-dispersion and high-speed dispersion. The prepared coating specimens were sprayed onto Q235 plates and tinplate plates by simple spraying. Test results show that the addition of modified basalt flakes (MBFs) helps to improve the mechanical and corrosion resistance of the coating. When 30% MBFs were added, the mechanical properties, acid and alkali resistance, and corrosion resistance of the coating reached the best, and the aging resistance was good. Among them, the adhesion of the coating could reach 15.36 MPa, and the coating surface did not show obvious flaring and peeling phenomenon after 1000 h of neutral salt spray test. The water contact angle of the coating increased from 77.77° to 81.31°. Meanwhile, the anti-corrosion performance of the base coating in 3.5 wt% NaCl solution was investigated using electrochemical impedance spectroscopy (EIS). The corrosion current density of the added modified basalt scale coating was in the order of 10⁻⁶, which was enhanced by one order of magnitude compared to that of the unmodified basalt scale. The annual corrosion rate of the MBFs coating was only 0.076588 mm·a⁻¹. The superior anticorrosive properties of silane coupling agent-modified basalt flake composite coatings provide a new meaning for the development of anti-corrosive coatings.

This paper presents obtaining a single-phase ferrite layer with low content of carbon (the average thickness is about 156–246 µm) on the surface of 0.45% carbon steel by precisely designing the cooling rate during heat treatment, and its mechanical properties show a graded change in the cross-section. It may be achieved by preparing gradient/multilayer materials with more commonly utilized structures or a specific performance. Combining with phase identification by employing electron backscatter diffraction (EBSD) of the layer in this study is BCC ferritic phases. Based on the examination of Continuous Cooling Transformation (CCT) curves, the following conclusions are given. Under the cooling process with gradient temperature, a ferrite layer first forms on the outer lower temperature surface of the 0.45% carbon steel and subsequently develops by pushing the surplus carbon to the inner higher temperature austenite region. It is corroborated by the experimental findings of carbon contents dispersion acquired by electron probe microanalyzer (EPMA). Finally, the experimental findings of grain orientations and size distribution defined by electron backscatter diffraction (EBSD) are given as requirements for microscopic interpretation of the combination of excellent strength and bending capabilities of materials. Furthermore, the experimental findings of oxidation precisely specified the cooling rate during heat treatment of Cu coating samples, which are defined as criteria for identifying the production mechanism of the surface ferrite layer. It provides a theoretical explanation and direct experimental proof for creating the ferrite layer on the surface.

By tailoring different microstructural features, this study verifies that the laser powder bed fusion (LPBF)-fabricated Ti-6Al-4V titanium alloy with a fully α/β lamellar structure exhibits excellent ductility at liquid nitrogen temperature. HT-800 was obtained by holding at 800 °C for two hours and then furnace-cooled, resulting in a microstructure consisting of residual martensitic α’ phase, lamellar α phase, and particulate β phase. The HT-900 was obtained by holding at 900 °C for two hours and then furnace-cooled, completely eliminating the multi-level martensitic α’ phase generated during the LPBF process and resulting in an α/β lamellar structure. HT-900 achieved an elongation of 11% at liquid nitrogen temperature, a 47% improvement over the HT-800. After low-temperature strain fracture, the proportions of 61.38° twin boundaries in the HT-800 and HT-900 were 21.4% and 26.4%, respectively, indicating that a substantial amount of deformation twinning is activated at liquid nitrogen temperature. Twinning induces the activation of slip systems by altering the orientation of surrounding grains. The coordinated plastic deformation of twinning and slip enhances the ductility of the HT-900 at 77 K. The results show that the LPBF-TC4 titanium alloy with a fully α/β lamellar structure exhibits superior, coordinated plastic deformation capabilities at 77 K, maintaining high strength while achieving greater ductility and fracture toughness.

In this paper, the interface microstructure, elements diffusion features at the interface, and bonding properties in nickel-based alloy/carbon steel clad composite prepared by vacuum hot-roll bonding were investigated, comprehensively. The influence of element distribution on the interface bonding strength was revealed as well. The results showed that there was a 13μm thick diffusion layer at the interface of nickel-based alloy/carbon steel composite plate, which was beneficial to a strong bond between nickel-based alloy and carbon steel, as well as the stable transition of mechanical properties in the thickness direction. Kirkendall voids and fine-grained structure (the grain size is about 41.5nm) were observable by peeling off the nickel-based alloy cladding, which greatly promoted element diffusion and enhanced the interfacial bonding strength of the nickel-based alloy/carbon steel composite plate. The diffusion coefficient of Ni at the interface was about 2 orders of magnitude larger than that of nanocrystalline Fe. The shear strength reached up to 453MPa, which was much higher than the minimum of 140MPa defined in ASTM A-264 specifications. Furthermore, in the shear test, the fracture occurred on the X52 carbon steel side at the contact rather than at the composite plate interface.