This study investigates the characteristics and formation mechanisms of pore defects in TC4 titanium alloy fabricated via selective laser melting （SLM） through numerical simulation and industrial computed tomography （CT） analysis. Numerical simulations find that the temperature at the laser beam spot is high， while the temperature away from the laser beam spot is low. After printing， microstructural characterization reveals well-overlapped melt tracks； however， both spherical and irregularly shaped pores are observed within the consolidated material. Using the same parameters as the simulation， the TC4 alloy prepared by SLM has a density of 97.7%. Microstructural analysis shows that the grains along the scanning direction and building direction are equiaxed and columnar crystals， respectively， and the microstructure is composed of primary β-Ti and α'/α-Ti. Metallographic structure， SEM images， and industrial CT reconstruction images demonstrate the presence of spherical and irregular pores in the material that are similar to the numerical simulation results. The appearance of spherical pore defects is due to the vapor pressure difference between the molten pool and the solid metal surface， which causes the gas at the interface to be carried into the molten pool without overflowing， ultimately remaining inside the material； the appearance of irregular pores is due to the uneven temperature distribution that makes it difficult for the pores enclosed inside the material to be completely filled by the liquid phase when the melt track passes over each other.

Selective laser melting （SLM） technology， with its unique solidification characteristics， can overcome the issue of coarse grain size in conventionally cast alloys. To achieve grain refinement and improve the mechanical properties of Cu-Al-Ni alloy prepared by SLM， the effects of key process parameters， including laser power and scanning speed， on the microstructure and mechanical properties perpendicular to and along the building direction are studied. The results show that fully overlapping melt tracks are present perpendicular to the building direction， in contrast， parallel to the building direction， it shows columnar grains that have grown epitaxially layer by layer. Both directions primarily consist of lath martensite. With increasing scanning speed at constant laser power， or with slightly decreasing laser power at fixed scanning speed， the melt tracks become narrower， and both the grains and martensite are refined. At a laser power of 280 W and a scanning speed of 850 mm/s， the resulting alloy exhibits the narrowest melt tracks， the finest grain size and martensitic structure， and the best mechanical properties. The hardness and compression strength measured along the building direction reach 251.2HV and 1465 MPa， respectively， while these perpendicular to the building direction reach 245.7HV and 1189 MPa， respectively. The refinement of grains and martensite is attributed to the high cooling rate inherent to SLM， and the improvement of mechanical properties is mainly due to grain refinement strengthening. The fine columnar grains， dense martensite and presence of twinning along the building direction result in higher interface density， which provides stronger resistance to dislocation slip， thereby leading to superior mechanical properties.

The isothermal oxidation mass gain test is adopted to study the high-temperature oxidation behavior at 800 ℃ of 310S stainless steel prepared by selective laser melting （SLM） and cold rolling （CR）. The microstructure， oxidation kinetics， and oxide scale structure of SLM-310S and CR-310S are systematically analyzed. The results show that both SLM-310S and CR-310S exhibit a single-phase austenite structure. SLM-310S forms a fish-scale structure due to molten pool stacking， characterized by fine and uniform grains， each containing numerous columnar and cellular subgrains. In contrast， CR-310S has typical polygonal austenite grains containing numerous twins. During oxidation at 800 ℃， the mass gain of SLM-310S is lower than that of CR-310S， with oxidation rate constants of 5.612×10^-4 mg²·cm^-4·h^-1 （SLM-310S） and 8.593×10^-4 mg²·cm^-4·h^-1 （CR-310S）， respectively. Both specimens develop a double-layer oxide scale： the scale on SLM-310S is approximately 2-4 μm thick and mainly composes of SiO₂， Cr₂O₃ and MnCr₂O₄， while that on CR-310S additionally contains a small amount of Fe-containing oxides， along with pore defects within the matrix. Owing to its excellent microstructural characteristics， SLM-310S exhibits slower oxidation kinetics and a denser oxide scale， demonstrating superior high-temperature oxidation resistance at 800 ℃ compared to CR-310S.

The friction pairs， such as the valve core and valves of seawater pumps， are under the conditions of seawater corrosion and wear （referred to as “tribocorrosion”）. The tribocorrosion resistance of materials directly affects the service life and safety reliability of marine engineering equipment. In-situ corrosion friction tests are adopted to quantitatively study the corrosion and wear mechanisms of three passivable alloys： titanium alloy （Ti75）， stainless steel （316SS）， and aluminum alloy （5083） in a 3.5%（mass fraction） NaCl aqueous solution. The results show that due to the lubricating effect of the erosion products of Ti75， corrosion and wear have a negative synergy， reducing the amount of wear， while the corrosion and friction of 5083 aluminum alloy and 316SS samples promote each other. The corrosion rate and tribocorrosion rate（2.25×10^-3 mm³/（N·m）） of 5083 aluminum alloy are both the highest， while the tribocorrosion rate of 316 stainless steel （6.78×10^-6 mm³/（N·m）） is the lowest. Among the three materials compared in this article， 316SS is the best material for manufacturing wear-resistant parts in seawater.

To address the functional failure of copper and its alloys caused by surface corrosion，a method combining micro-arc oxidation and silicone oil heat treatment is proposed to construct a long-lasting corrosion-resistant and hydrophobic film layer on the surface of copper-zinc alloys. Firstly，through micro-arc oxidation and doping with ZrO₂ particles，a porous microstructure is constructed in-situ on the surface of copper-zinc alloys，and rigid nanoparticles are introduced. Together with micropores，they form the multi-level micro-nano structure required for a hydrophobic surface. Secondly，the oxide film layer is sealed and modified with a dimethyl silicone oil solution. Finally，the silicone-oil-modified oxide film layer samples are heated under a heat-treatment environment to reduce the surface energy of the oxide film layer and achieve hydrophobicity. The surface morphology，chemical composition，and phase composition of the hydrophobic film layer are characterized by scanning electron microscopy （SEM），energy dispersive spectroscopy （EDS），and X-ray diffraction （XRD），respectively. The wettability，corrosion resistance，and durability of the hydrophobic film layer are tested using a contact angle measuring instrument，an electrochemical workstation，and a tape peeling test，respectively. The results show that the main phases on the surface of the hydrophobic film layer are CuO，ZnO，α-Al₂O₃，γ-Al₂O₃，ZrO₂，and SiO₂. Compared with the copper-zinc alloy substrate，the corrosion current density of the hydrophobic film layer is reduced by four orders of magnitude. The water contact angle increases from the original 64.1° to 139.2°，and the surface adhesion energy decreases from 45.331 mJ/m² to 3.554 mJ/m². After 150 tape peeling tests，the contact angle of the prepared hydrophobic film layer surface is still higher than 120°，maintaining good hydrophobicity. This study can provide certain experimental basis and fundamental guidance for the surface corrosion protection of copper and copper alloys.

TiC particles that can be wetted by iron-based alloys at elevated temperatures act as the hard phase. The TiC/Fe composite coatings featuring alternating hard and soft phases are cladded on the surface of Q235 steel plates to enhance their service life under wear resistant conditions. The results show that the TiC/Fe composite coatings prepared by laser cladding form a composite structure with alternating hard TiC phase and soft γ-Fe phase. However，when the area ratio of the soft phase to the hard phase is large （greater than 1.8），the “high hardness-antifriction” TiC/Fe composite coatings are not obtained. When the area ratio of the soft γ-Fe phase to the hard TiC phase is approximately 1∶1，a “high hardness-antifriction” synergistic effect is achieved，that is，the average hardness of the alloy coatings is as high as 1300.39HV_0.2，and the average coefficient of friction is only 0.1127. The wear mechanism of the iron-based alloy coatings without TiC particles is mixed a wear mechanism of abrasive wear，adhesive wear and oxidative wear. After adding TiC particles，the wear mechanism of the alloy coatings are mainly slight oxidative wear，and with the increase of TiC particles addition，the oxidative wear of the alloy coatings weakens.

To improve the corrosion resistance of waterborne epoxy coating， chitosan is adsorbed onto the surface of multi-walled carbon nanotubes via surface-deposition crosslinking with glutaraldehyde as the crosslinking agent. Then， stearic acid has been grafted using a water-soluble coupling agent，1-ethyl-（3-dimethylaminopropyl）carbodiimide hydrochloride （EDC·HCl），to synthesize stearic acid/chitosan-modified multi-walled carbon nanotubes （SA/CS-CNTs）. Aqueous epoxy anticorrosive coatings are prepared by blending SA/CS-CNTs with aqueous epoxy resin. The structure of SA/CS-CNTs has been characterized， and the corrosion resistance performances of the coatings have been explored. The results show that the epoxy resin with 0.5% （mass fraction）SA/CS-CNTs filler has the best corrosion resistance. Compared with the pure waterborne epoxy coating， its low-frequency impedance modulus is increased by about 5 orders of magnitude， the corrosion inhibition efficiency increases to 99.66%， and the water contact angle reaches 104.2°. The corrosion potential increases by 0.39 V，and the corrosion current density decreases from 4.17×10^-6 A·cm^-2 to 1.44×10^-8 A·cm^-2. After being immersed in 3.5% NaCl solution for 96 h， its impedance modulus is still above 10⁷ Ω·cm².

To tackle the challenges of high-temperature phase stability deterioration and sintering densification in zirconia-based thermal barrier coating ceramic materials during prolonged service at temperatures exceeding 1200 ℃， this study utilizes a highly efficient and cost-effective solid-phase synthesis process to fabricate La₂Zr₂O₇-SYSZ composite ceramics with a hypoeutectic composition. We conduct a comprehensive investigation into the impact of 1450 ℃ heat treatment on the high-temperature microstructural stability， evolution， and grain growth kinetics of these composite ceramics using field emission scanning electron microscopy （SEM） and energy dispersive X-ray spectroscopy （EDS）. The experimental findings reveal that La₂Zr₂O₇-SYSZ composite ceramics， sintered at 1600 ℃ for 6 h， display equiaxed or near-equiaxed grain morphology， with an average grain size of （2.9±0.31） μm. Following heat treatment at 1450 ℃ for durations ranging from 50 h to 300 h， the grain size distribution curves exhibit a notable rightward shift and broadening， with the average grain size gradually increasing to （4.7±0.33） μm. Initially， the grain size distribution follows a single-peak normal distribution pattern； however， as the heat treatment time is extended to 150-300 h， it gradually evolves into a dual-peak normal distribution. The composite system demonstrates a grain growth activation energy of （351.79±19.21） kJ/mol and a growth exponent （n=2.3）， suggesting that grain growth is predominantly governed by lattice-diffusion-controlled pinning effects. This research offers vital theoretical underpinnings and technical references for the development of next-generation anti-sintering thermal barrier coating materials.

As a vital successor to conventional oil and gas resources， shale-gas development inevitably generates drilling-cuttings hazardous waste. Finding ways to exhaust and up-value this waste becomes another pressing problem for the industry. In this study， deoiled residue of drilling cuttings （DRDC） is used as the main feedstock， added with low-grade bauxite as supplementary alumina source and potassium feldspar as fluxing agents. A 50 kg/h pilot-scale line installed at the extraction site is operated continuously for 25 days to systematically evaluate how the deoiled residue content and sintering temperature affect the bulk density， apparent density and breakage ratio of the ceramic proppants. The results show that the roundness and sphericity for all proppant products exceed 0.9. Both bulk and apparent densities of the ceramic proppants decreases progressively with increasing addition of the drilling cutting， whereas the breakage ratio rises. Raising the sintering temperature increases the bulk and apparent densities but reduces the breakage ratio. At the preparation parameters including the content of DRDC of 5%（mass fraction） and sintering temperature of 1300 ℃， ceramic proppants with a breakage ratio of 3.01% measured at 52 MPa closure stress can be obtained. Ceramic proppants meeting the standard of SY/T 5108—2014 are produced under all twenty producing conditions.

A method of continuous flash pretreatment combined with oxidative amination grafting is proposed to prepare the cross-linked biobased material which can be hot processed. The effects of thermoforming processing methods， decrosslinking recovery and reprocessing on the properties of the materials are investigated. The results show that when the mass ratio of sodium periodate to plant fiber is 0.3 and the molar ratio of amine to aldehyde is 1.4， the sheet exhibits excellent mechanical properties and good hydrophobicity. The expansion rates of bending strength and water absorption are 58.2 MPa and 15.7%， respectively， and the tensile strength is increased to 69.9 MPa after dynamic molding. The water absorption expansion rate is reduced to 11.2%. The results show that the strength of 3 h， 80 ℃ hydrolyzed products can reach 55.1 MPa and the properties can be maintained to 78.9% after crushing， hydrolyzing， and reforming the dynamic moulded sheets. The results prove the feasibility of oxide-amination modification method and dynamic die molding to prepare high performance plant fiber materials， which is helpful to realize the recycling of plant fiber and the development of environmentally friendly biomass materials.