Abstract:The impact of casting defects on the weldability of K4951 superalloy was investigated using tungsten inert gas (TIG) welding. The as-cast K4951 superalloy samples with prefabricated U-shaped grooves of varying depths and widths were TIG welded, and the microstructures, cracks morphology, and precipitated phases were analyzed using optical microscope, scanning electron microscope, transmission electron microscope, and energy dispersive X-ray spectrometer. The results reveal that the dimensions of casting defects significantly affect the weldability of K4951. Deep defects (greater than 2 mm) lead to rapid crack propagation, while wider defects can moderate the propagation process of cracks. Elemental segregation and the formation of precipitated phases, such as MC carbides, are observed in the fusion zone, contributing to welding cracks. An optimal groove aspect ratio (depth-to-width) between 0.2 and 0.5 minimizes crack formation tendency and enhances tensile strength, resulting in a mixed brittle-ductile fracture mode of joint after high-temperature tensile testing.

Abstract:ZGH401 alloy was prepared under varying laser power levels and scanning speeds by the orthogonal test method using selective laser melting (SLM). The effect of different energy densities on microstructure and mechanical properties of the formed alloy was investigated. The microstructure of ZGH401 was analyzed by scanning electron microscope, electron back-scattered diffraction, and electron probe microanalysis. The results show that the defects of the as-built ZGH401 are gradually reduced, the relative density is correspondingly enhanced with increasing the energy density, and the ultimate density can reach 99.6%. An increase in laser power leads to a corresponding rise in hardness of ZGH401, while a faster scanning speed reduces the residual stress in as-built ZGH401 samples. In addition, better tensile properties are achieved at room temperature due to more grain boundaries perpendicular to the build direction than parallel to the build direction. The precipitated phases are identified as carbides and Laves phases via chemical composition analysis, with fewer carbides observed at the molten pool boundaries than within the molten pools.

Abstract:The microstructure of single crystal superalloy is relatively simple, consisting primarily of γ dendrites and γ/γ′ eutectics. During the directional solidification process of Ni-based single crystal superalloys, withdrawal rate is a critical parameter affecting the spatial distribution of γ/γ′ eutectic along gravity direction. The results show that the γ/γ′ eutectic fraction of the upper platform surface is always higher than that of the lower one, regardless of withdrawal rate. As the withdrawal rate decreases, there is a significant increase in γ/γ′ eutectic fraction on the upper surface, while it decreases on the lower surface. The upward accumulation of γ/γ′ eutectic becomes more severe as the withdrawal rate decreases. It is also found that the percentage of Al+Ta is positively correlated with the γ/γ′ eutectic fraction. Thermo-solute convection of Al and Ta solutes in the solidification front is the prime reason for the non-uniform distribution of eutectic. The non-uniform distribution of γ/γ′ eutectic cannot be eliminated even after subsequent solution heat treatment, resulting in excess eutectic on the upper surface and thus leading to the scrapping of the blade.

Abstract:The formation mechanism of freckle defects in large-sized UGTC47 directionally-solidified columnar crystal blades for heavy-duty gas turbines and their effect on the stress rupture property were investigated using optical microscope, scanning electron microscope, and endurance performance test. The results indicate that freckle defects form in both the middle and root regions of the blade tenon, whose formation mechanism is the density inversion caused by liquid phase segregation, resulting in fluid convection under the action of gravity, and leading to the fracture of dendrite arms and the formation of freckles. At 900 ℃/380 MPa, the proportion of freckle area has a significant impact on the endurance performance of the UGTC47 alloy. With the increase in freckle content, the stress rupture life of the alloy is decreased from 131.83 h without freckle defects to 33.66 h with freckle content of 62%.

Abstract:Reliable zirconia-toughened alumina (ZTA) composite ceramic/GH3536 nickel-based alloy brazing joints were fabricated using AgCuAlTi filler. The effects of brazing temperature and holding time on the interfacial microstructure and shear strength of the brazing joints were investigated. The typical interfacial structure of the joint brazed at 980 ℃ for 10 min is ZTA/TiO+Ti₃(Cu,Al,Ni)₃O/Ag(s,s)+Cu(s,s)/AlNi₂Ti+Ti₂Ni/Fe-Cr+Ni-Fe-Cr/GH3536. The two components of Al₂O₃ and ZrO₂ in the ceramic matrix participate in the interfacial reactions together. Ti₃Cu₃O is formed by Al₂O₃ with Ti and Cu in the liquid filler and ZrO₂ reacts with Ti and Cu to form TiO and Ti₃Cu₃O. Ti₃(Cu,Al,Ni)₃O is formed through the solid-solution of Al and Ni into Ti₃Cu₃O. With the increase in brazing temperature (940–980 ℃) and holding time (1–10 min), TiO, Ti₃(Cu,Al,Ni)₃O and AlNi₂Ti layers are thickened, and the joint brazed at 980 ℃ for 10 min has the maximum shear strength of 123 MPa. When the brazing temperature exceeds 980 ℃ or holding time is longer than 10 min, TiO on the ceramic side is converted to Ti₃(Cu,Al,Ni)₃O. Meanwhile, a large amount of generated AlNi₂Ti excessively consumes Ti in the filler, thereby hindering the generation of Ti₃(Cu,Al,Ni)₃O. So the Ti₃(Cu,Al,Ni)₃O layer is no longer continuous, which ultimately degrades the shear strength of the joint.

Abstract:The effects of initial grain size and hot deformation parameters on hot deformation characteristics of high-quality GH4738 alloy under different small deformation conditions were analyzed. The microstructure evolution and softening mechanisms during hot working process and sub-solid solution treatment process were investigated by OM, EBSD and TEM analyses. The results indicate that the flow stress is increased with the increase in initial grain size, especially under the lower hot working temperature, and the increment is decreased with the increase in deformation temperature. The volume fraction of dynamic recrystallization in GH4738 alloy has a strong dependence on the initial grain size. Increasing the hot deformation temperature and engineering strain can promote the process of dynamic recrystallization of this alloy. The dynamic recrystallization mechanisms of GH4738 alloy are mainly based on the discontinuous dynamic recrystallization mechanism of nucleation of grain boundary bulging. In the meantime, during the process of dynamic recrystallization and grain growth, the grain boundary undergoes small planarization due to atomic migration, resulting in a quasi-right angle staged grain boundary. The static recrystallization occurs during the sub-solid solution treatment process, and the grains are refined to a great extent due to the incomplete re-dissolution strengthening γ' phase, which can promote the nucleation of static recrystallization.

Abstract:Different thermal exposure aging treatments were performed on DD6 nickel-based single crystal superalloy to obtain different degraded microstructures. The mechanism of microstructural degradation evolution, and corresponding residual strength and fracture mechanism were studied. Parametric characterization methods of microstructural degradation degree were explored, and a quantitative mapping relationship between residual strength and microstructural degradation degree was established. The results indicate that during thermal exposure aging process, γ′ phase undergoes dissolution or growth according to Ostwald ripening mechanism. After aging at 980 ℃ for 1190 h and 1100 ℃ for 100 h, the content of γ′ phase almost reaches thermal equilibrium state. With the increase in temperature and time, the width of γ and γ′ phases will continue to coarsen and gradually stabilize. Finally, the width of γ phase is about 400 nm and the width of γ′ phase is about 760 nm. While coarsening, DD6 alloy undergoes rafting under the internal γ/γ′ phase mismatch stress or applied loads. Coarsening and rafting both reduce the strength of DD6 alloy. Considering the effects of coarsening and rafting, the microstructure size parameter ωλ² is used to establish a good quantitative mapping relationship with residual strength, and this characterization method for microstructural degradation does not depend on microstructure size in the initial state.

Abstract:The influencing mechanisms of P content on the creep rupture properties of GH4738 alloy and the optimum additive range of P element in this alloy were investigated by OM, SEM, TEM, and EBSD microscopic analyses. The results show that the creep rupture strength of the alloys shows a tendency of firstly increasing and then decreasing with the increase in P content. The optimal addition amount of P ranges from 0.0040wt% to 0.0091wt%, and the fracture morphology shows a mixed fracture type. With continuously increasing the P element, the endurance life is decreased by 30%–50%, the persistent plasticity is decreased by 20%–70%, and the fracture mode changes to brittle intergranular fracture. The main reasons are as follows. P, as a type of grain boundary segregation element, when its content is smaller, the segregated P element occupies the vacancy at the grain boundary to decease the free energy of grain boundary, thereby increasing the nucleation rate of carbides. Meanwhile, the uniformly dispersed M₂₃C₆-type carbides along grain boundaries can inhibit crack propagation and improve grain boundary strength, ultimately enhancing the creep resistance of the alloys. When P content is greater than the critical value, it has a tendency to solute into MC-type carbides. Consequently, with further increase in P content, the amount of MC-type carbides at grain boundaries is increased while M₂₃C₆-type carbides are decreased relatively. The blocky MC-type carbides become unevenly distributed along grain boundaries, leading to a continuous degradation in the creep resistance of the experimental alloys.

Abstract:To improve the compactness and properties of C/C-SiC-ZrC composites produced by precursor infiltration and pyrolysis (PIP) method, the low-temperature reactive melt infiltration (RMI) process was used to seal the composites using Zr₂Cu as the filler. The microstructure, mechanical properties, and ablation properties of the Zr₂Cu packed composites were analyzed. Results show that during Zr₂Cu impregnation, the melt efficiently fills the large pores of the composites and is converted to ZrCu due to a partial reaction of zirconium with carbon. This results in an increase in composite density from 1.91 g/cm³ to 2.24 g/cm³ and a reduction in open porosity by 27.35%. Additionally, the flexural strength of Zr₂Cu packed C/C-SiC-ZrC composites is improved from 122.78±8.09 MPa to 135.53±5.40 MPa. After plasma ablation for 20 s, the modified composites demonstrate superior ablative resistance compared to PIP C/C-SiC-ZrC, with mass ablation and linear ablation rates of 2.77×10^-3 g/s and 2.60×10^-3 mm/s, respectively. The “self-transpiration” effect of the low-melting point copper-containing phase absorbs the heat of the plasma flame, further reducing the ablation temperature and promoting the formation of refined ZrO₂ particles within the SiO₂ melting layer. This provides more stable erosion protection for Zr₂Cu packed C/C-SiC-ZrC composites.

Abstract:Zirconium alloy cladding materials inevitably undergo hydrogen absorption in the processing and operation process of the reactor, and its static and dynamic mechanical properties are closely related to the hydrogen content. Samples with hydrogen content ranging from 23 μg/g to 132 μg/g were obtained using the method of gas-phase hydrogen charging, and the influence of hydrogen content on static/dynamic mechanical properties of Zr-Sn-Nb-Fe alloy was studied. The results show that the effect of weak hydrogen charging on the ultimate tensile strength, yield strength, and elongation of zirconium alloy is not obvious. There are a large number of dimples on the fracture surface of the tensile sample before and after hydrogen charging, which is a typical ductile fracture. However, the impact toughness of Zr-Sn-Nb-Fe alloy decreases significantly after trace hydrogen charging. The impact sample without hydrogen charging shows the mixed fracture mechanism of ductile fracture and microcleavage fracture. The increase in hydrogen permeability leads to the emergence of hydride, and the deformation of high strain rate under the impact loading condition leads to secondary cracks in the microstructure. The initiation and expansion of the secondary cracks is the main reason for the reduction of the impact toughness.

Abstract:The TZM alloys with different contents of ZrO₂ were prepared by powder metallurgy and rolling, and the grain size, hardness, and abrasive wear resistance of TZM alloy were studied. The abrasive wear test of TZM alloy was conducted under the conditions of 10, 15, and 20 N and abrasive particle sizes of 7, 11, 18, and 38 μm. The results show that the added ZrO₂ particles in TZM alloy are mainly distributed at the grain boundaries. The grains of TZM alloy containing 1.5wt% ZrO₂ are significantly refined, and the hardness is increased by 16%. The wear test results show that TZM alloy containing 1.5wt% ZrO₂ has the lowest mass loss rate and excellent wear resistance under all loads and abrasive sizes, and the wear performance is improved by 12%. The ZrO₂ with high hardness becomes the main bearer of the load, and as the second-phase, it hinders the abrasive particles from entering the matrix and effectively resists the scratch of the abrasive particles, which is the main reason for the excellent wear resistance.

Abstract:The Hall-Petch slope k represents the magnitude of grain boundary strengthening. A strong orientation dependence of the k value of pure zirconium (Zr) is revealed in this research. Namely, k value of the pure zirconium plate along the RD-tension (84 MPa·μm^1/2) is much lower than that along the TD-tension (220 MPa·μm^1/2), where RD and TD are the rolling direction and transverse direction of the plate, respectively. By combining experiments with the visco-plastic self-consistent model, the deformation mechanisms of pure zirconium plate were analyzed. The grain size of the plates are increased with the increase in annealing temperature, and the texture type do not change. Different deformation mechanisms are activated along different loading directions: prismatic slip dominates during RD-tension, whereas prismatic and basal slips collaborate to deform during TD-tension, while the {} twinning is also activated along TD. The orientation-dependent mechanism of the k value in pure zirconium was revealed based on the activation stress difference σ_d and the geometric coordination factor m' between neighbouring grains. The results indicate that the geometric coordination factor m' between neighbouring grains under RD-tension (0.67) is similar to that under TD-tension (0.71), while the activation stress difference σ_d under TD-tension (103.72 MPa) is significantly higher than that under RD-tension (32.17 MPa), resulting in a higher k value under TD-tension compared to RD-tension.

Abstract:High-purity indium finds extensive application in the aerospace, electronics, medical, energy, and national defense sectors. Its purity and impurity contents significantly influence its performance in these applications. High-purity indium was prepared by combining zone refining with vacuum distillation. Results show that the average removal efficiency of impurity Sb can approach 95%, while the removal efficiency of impurities Sn and Bi can reach over 95%, and the removal efficiency of Si, Fe, Ni, and Pb can reach over 85%. Ultimately, the amount of Sn and Sb impurities is reduced to 2.0 and 4.1 μg/kg, respectively, and that of most impurities, including Fe, Ni, Pb, and Bi, is reduced to levels below the instrumental detection limit. The average impurity removal efficiency is 90.9%, and the indium purity reaches 7N9.

Abstract:High-performance pure nickel N6/steel 45# composite plate (N6/45#) was prepared using explosive welding technique. The microstructure of the interface and nearby regions was characterized and analyzed by optical microscope, scanning electron microscope, electron backscatter diffraction, and mechanical property testing, and the microstructural features and mechanical properties of the explosive welding interface were explored. The results show that along the direction of explosive welding, the pure nickel N6/steel 45# composite plate interface gradually evolves from a flat bond to a typical wavy bond. The grains at the crests and troughs exhibit high heterogeneity, and the closer to the interface, the finer the grains. Recrystallization and low-stress deformation bands are formed at the bonding interface. Nanoindentation tests reveal that plastic deformation occurs in the interfacial bonding zone, and the nanohardness values in the crest regions are higher than that in the trough regions. The tensile strength of the N6/45# interface is 599.8 MPa, with an average shear strength of 326.3 MPa. No separation phenomenon is observed between N6 and 45# after the bending test.

Abstract:The high-entropy alloy composite coatings AlCu₂Ti(NiCr)₂-(WC)_x (x denotes powder feeding speeds, including 0, 25, 50, and 75 r/min) were prepared by plasma cladding using a hybrid mode of AlCu₂(NiCr)₂Ti cable-type welding wire (CWW) and tungsten carbide (WC) powder. The effect of WC powder feeding speed on the microstructure, hardness, and wear properties of the prepared coatings was investigated. The results show that the coatings consist of body-centered cubic main phases and face-centered cubic secondary phases, with carbide reinforcement phases formed due to the addition of WC. The hardness and wear resistance of the coatings are significantly improved compared to the TC11 substrate. When WC powder feeding speed is set at 50 r/min, the coating exhibits optimal wear resistance, with a minimum volume wear rate of 8.5869×10^-6 mm³·N^-1·m^-1, greatly improving the wear properties of TC11 surface. The coincident CWW-powder plasma cladding provides a viable method for the preparation of high-entropy alloy composite coatings with enhanced wear resistance.

Abstract:To verify the wear resistance and erosion resistance of Ti-doped Ta₂O₅ coating (TTO), a series of TTOs were prepared by magnetron sputtering technology by controlling the power of the Ti target. The change of growth structure, microstructure, and tribological properties of TTOs with Ti target power was studied. After the erosion test, the variation of erosion damage behavior of TTOs with mechanical properties under different erosion conditions was further studied. The results show that the TTOs eliminate the roughness, voids, and defects in the material due to the mobility of the adsorbed atoms during the growth process, and a flat and dense smooth surface is obtained. Tribological tests show that the TTOs are mainly characterized by plastic deformation and microcrack wear mechanism. Higher Ti target power can improve the wear resistance of TTOs. Erosion test results reveal that the impact crater, furrow, micro-cutting, brittle spalling, and crack formation are the main wear mechanisms of the TTOs samples under erosion conditions.

Abstract:Zr-based alloys prepared by powder metallurgy have the advantages of few macroscopic defects and low cost. However, the high content of oxygen and poor plasticity of this alloy have become the main obstacles restricting its applications. The plasticity of Zr-based alloys prepared by powder metallurgy was improved by doping rare earth hydrides to reduce the O content in alloy matrix. The effects of YH₂ addition content on the microstructure and mechanical properties of Zr-Nb alloys were investigated. The results show that the O content in the matrix is significantly decreased due to the Y₂O₃ formed by doped YH₂ with O in the matrix. On the one hand, more plastic β phase can be retained by the reduction of O content in matrix, which is beneficial to the improvement of plasticity. On the other hand, effects of the dispersion strengthening of Y₂O₃ particles and the grain refinement caused by dislocation pinning by formed Y₂O₃ can both contribute to the improvement of strength. Taking the Zr-Nb alloy added with 2.4wt% YH₂ as an example, the dynamic compressive strength is decreased by 16% and the plasticity is increased by 140% compared with the alloy without YH₂ addition. Decoupling analyses were conducted on the effects of oxygen content, phase composition and grain size on the strength and plasticity of the alloy.

Abstract:The mechanical properties, microstructure, and residual stress of the cold-rolled and aged samples of C19400 alloy were systematically studied. The results show that the maximum tensile strength of the rolled alloy can reach 546 MPa. In addition, the results of both macroscopic and microscopic residual stress show that the residual stress of the rolled alloy is higher, indicating that residual stress is mainly generated during the nonuniform cold rolling plastic deformation process. This is verified in the kernel angle misorientation (KAM) distribution map, because the KAM value of the rolled alloy is higher than that of the aged alloy. At the same time, the evolution of macroscopic and microscopic textures in C19400 alloy was revealed. The results show that the texture types in both rolled and aged alloys are Brass (011)211, Copper (112)111, and S (123)634 deformation textures as well as recrystallized Cube (001)100 textures. And the intensity and volume fraction changes of Copper (112)111 textures are consistent with those of residual stress, which indicates that the presence of Copper (112)111 texture is more conducive to the generation of residual stress.

Abstract:An Al-8Zn-3Mg-1.05Cu alloy was designed according to the solid solubility of Zn, Mg and Cu elements in Al matrix. Then, the hot-rolled plate was subjected to solid solution treatment. The results of SEM and XRD show that the solid-solution microstructure with only a small amount of compound residue is obtained after solid solution treatment. Subsequent cold rolling, solid solution and aging treatment of the alloy were carried out. The EBSD results indicate that the alloy obtains incompletely recrystallized structure after cold rolling and solid solution treatment. The KAM diagram shows that the dislocation density in the incompletely recrystallized zone is high. The alloy after solid solution treatment exhibits favorable tensile properties, with the yield strength of 458.61 MPa and elongation of 15.6%. The TEM results after aging treatment show that a large number of fine MgZn₂ phases are precipitated in the microstructure. The average size of MgZn₂ phase is about 6.40 nm, which is notably smaller than that in the reported alloys. After aging treatment, the alloy obtains ultra-high strength and good plasticity with the yield strength and elongation of 729 MPa and 10.37%, respectively. The strength composition of the alloy was calculated, and the precipitation strengthening contribution value of fine MgZn₂ phase is 348.48 MPa. The calculated yield strength value matches well with the experimental value.

Abstract:The tensile properties and anisotropy of different batches of ultra-thin titanium foils for bipolar plates were studied through room temperature tensile tests. The effects of texture, surface quality, and deformation twin on the tensile anisotropy of ultra-thin titanium foil was analyzed using detection methods such as EBSD and 3D profilometer, revealing the main influencing factors of tensile anisotropy. The results show that there is significant tensile anisotropy in all batches of foil, and the elongation and strength in the rolling direction are higher than those in the transverse direction. Compared with the tensile strength, the elongation of the material has a higher sensitivity to anisotropy. The surface quality of foil is the dominant factor affecting its tensile anisotropy. During the preparation process, improving the surface quality can weaken the anisotropy of the foil, thereby significantly improving its comprehensive mechanical properties.

Abstract:The microstructure evolution and deformation mechanism at room temperature and cryogenic temperature of cryogenic titanium alloy bars were investigated through controlling Mo equivalent. The results show that with the increase in Mo equivalent, β phase stability is improved, which limits the precipitation of α phase. High-Mo-equivalent alloy forms single-phase β grains without α phase precipitation. As for the low-Mo- equivalent alloy, the basketweave microstructure occurs. At room temperature, the plasticity of stable β alloy Ti-38V is higher, which is attributed to bcc-β phase possessing more slip systems than hcp-α phase. The slip ability of β phase is better than α phase, leading to the excellent plastic deformation ability of β phase. As a result, a large number of dimples occur in the tensile fracture. The strength of (α+β) alloy Ti-3Al-6Mo is higher, which is mainly caused by the strengthening effect of interweaved α lamella. The higher Schmid factor of the (α+β) titanium alloy makes the dislocation slip easier, which makes the dislocation slip act as the primary deformation mechanism at both room and cryogenic temperatures, while deformation twins can also be activated at cryogenic temperature. For the stable β titanium alloy, stress concentration occurs at the grain boundary because of dislocation pile-up. The higher V content increases β stability, which makes the fracture sample at cryogenic temperature without stress-induced mechanical twins. Consequently, the deformation ability is poor and it exhibits brittle fracture characteristics at cryogenic temperature.

Abstract:The Ti/Al composite sheets were fabricated by explosive welding (EXW) and cold rolling (CR) with a reduction of 0%, 27% and 55%. Then, the EXW-cold rolled Ti/Al composite sheets were annealed at 600, 625 and 650 ℃ under air and vacuum environment for different durations, and the annealing time was up to 576 h. The effects of temperature, rolling reduction and vacuum environment on the growth of interfacial layer of Ti/Al composite sheets were investigated. The results show that two modifications of titanium trialuminide (TiAl₃(h) and TiAl₃(l)) are formed at Ti/Al interface, and the higher the temperature, the larger the volume fraction of TiAl₃(h) phase. Furthermore, the average grain size of TiAl₃ phase is also increased with the increase in annealing temperature. The growth of interfacial layer at Ti/Al interface under different conditions can be divided into three stages: the first stage is controlled by oxide films, the second stage is controlled by chemical reaction, and the last stage is controlled by diffusion. At the stage controlled by oxide films, the kinetics constant is very little, and the interfacial layer thickness is relatively uniform. At the stage controlled by chemical reaction, there are some large humps at the interfacial layer, and the thickness uniformity is very poor. At the early stages controlled by oxide films and chemical reaction, the higher the annealing temperature, the larger the kinetics constant of TiAl₃ phase. Due to the opposite effect of grain size and temperature on the interdiffusion coefficient of TiAl₃ phase,at the early stage of diffusion-controlled growth, the higher the annealing temperature, the greater the kinetics constant. At the later stage of diffusion-controlled growth, the higher the temperature, the smaller the kinetics constant. The thickness uniformity of interfacial layer becomes better with the prolongation of annealing time at different temperatures, and the higher the temperature, the better the thickness uniformity at the same annealing time. At 600 ℃, cold rolling can improve the growth rate and thickness uniformity of TiAl₃ phase at chemical reaction-controlled stage and early diffusion-controlled stage, and the greater the reduction, the faster the growth rate and the better the thickness uniformity. However, at 650 ℃, cold rolling has little effect on the growth rate and thickness uniformity of TiAl₃ phase at chemical reaction-controlled and diffusion-controlled stages. At the stage controlled by oxide films, the kinetics constant under vacuum environment is larger than that under air environment. At the chemical reaction-controlled and diffusion-controlled stages, the kinetics constant under vacuum environment is almost the same as that under air environment, but the thickness uniformity of TiAl₃ phase under vacuum environment is better than that under air environment.

Abstract:The problem of ice accumulation on solid surface has a significant impact on both industrial sectors and human life, so exploring novel anti-icing materials is of great importance. In this study, polydimethylsiloxane with low surface energy was employed onto aluminum plates as a binder. Fe₃O₄ and Fe₃O₄/SiO₂ dispersion liquids were separately sprayed to form hydrophobic coatings with photothermal effect. Fe₃O₄ provides photothermal effect and forms a certain micro-nano rough structure on the coating surface. When SiO₂ is added, the hydrophobicity is further enhanced, with a water contact angle reaching 155°. This coating greatly delays the icing time and accelerates frost melting. Under one-sun illumination, the temperature rise can reach 71.8 ℃. The coating exhibits self-cleaning capability, effectively preventing severe contamination. It also demonstrates certain resistance to windblown sand impact and excellent mechanical stability, thereby providing a new direction for the development of anti-icing materials.

Abstract:Cu-Cr-Zr alloy is widely used in communication electronics, rail transit, aerospace and other fields, and improving its strength and conductive properties is a research focus in recent years. In this research, Cu-1Cr-0.1Zr and Cu-1Cr-0.1Zr-0.069La alloy ingots were designed and prepared, and treated by solution-warm rolling-cold rolling-preaging-cold rolling-aging processes. The macrostructure and microstructure of two alloys were analyzed by optical microscope, scanning electron microscope and transmission electron microscope. The hardness and conductivity of the alloys were measured by microhardness tester and eddy-current metal conductivity meter. The results show that after 400 ℃ warm rolling, a small amount of nanoscale Cr phase with fcc structure is precipitated from the alloy matrix. The primary Cr phases are distributed in spherical and rod-like forms at grain boundaries and within grains, and rare earth La is wrapped around the outer layer of Cr phase to form a core-shell structure, which inhibits the growth of Cr phase. After 83% cold rolling+400 ℃×2 h aging treatment, Cu-1Cr-0.1Zr-0.069La alloy reaches the peak hardness of 199.8 HV and the conductivity of 66.5%IACS, which is an increase in peak hardness of 20 HV and a decrease in conductivity of 3.5%IACS compared to Cu-1Cr-0.1Zr alloy. After further 44% cold rolling, Cu-1Cr-0.1Zr-0.069La alloy reaches the peak hardness of 212.9 HV, tensile strength of 640 MPa and the conductivity of 74.4%IACS after aging at 400 ℃ for 4 h. The peak hardness of Cu-1Cr-0.1Zr-0.069La alloy is 17.2 HV higher than that of Cu-1Cr-0.1Zr alloy, and the conductivity is decreased by 4.7%IACS.

Abstract:The effect of Y on the corrosion resistance of homogenized Mg-6Zn-0.25Ca was studied. The microstructure and corrosion behavior of the homogenized Mg-6Zn-0.25Ca and Mg-6Zn-1Y-0.25Ca alloys were characterized by XRD, OM, SEM, mass loss, hydrogen evolution and polarization curve experiments. The results show that the secondary phase of homogeneous Mg-6Zn-0.25Ca alloy is Mg₂Ca, and the average grain size increases slightly after the addition of Y element, while the Mg₂Ca phase decreases. New secondary phases Mg₁₂ZnY and Mg₃Y₂Zn₃ are also formed, and the volume fraction of them increases and the distribution is more uniform. This enables a denser and more compact corrosion film to form on the magnesium matrix during the corrosion test, which can act as a barrier. The Mg₁₂ZnY and Mg₃Y₂Zn₃ are distributed near the grain boundary or between the dendrites, which significantly reduces the electrochemical activity of the alloy in corrosive solution. Thus, the hydrogen precipitation of Mg-6Zn-0.25Ca alloy is reduced in 3.5wt% NaCl solution. By increasing the Y element, the self-corrosion potential of Mg-6Zn-0.25Ca alloy is increased and self-corrosion current density is reduced, thereby improving the corrosion resistance of homogeneous Mg-6Zn-0.25Ca alloys. Therefore, the corrosion resistance of Mg-6Zn-1Y-0.25Ca alloy is much higher than that of Mg-6Zn-0.25Ca alloy.

Abstract:To investigate the effect of secondary phases on the microstructure and mechanical properties of Mg-Sn-Zn-Ca alloys, this study employed both isothermal and incremental temperature rolling processes on Mg-2Sn-2Zn-1Ca magnesium alloy sheets. Mechanical tests reveal that the yield strength (161.3 MPa) and elongation (6.6%) of the isothermally rolled sheet are significantly lower than those of the incremental-temperature-rolled sheet, which exhibits a yield strength of 295.6 MPa and an elongation of 20.9%. Microstructural analyses indicate that the isothermally rolled sheet exhibits a coarse-grain microstructure with a large number of deformation twins. In contrast, the incremental temperature rolling process effectively decreases the grain size to 10.17 μm through the regulation of secondary phase. During isothermal rolling, an increase in the content of secondary phases (Mg_xZn_y) leads to larger particle sizes, which induces stress concentration, thereby contributing to premature material failure. Conversely, incremental temperature rolling facilitates interactions between secondary phases and high-density dislocation regions, acting as preferential nucleation sites during recrystallization, and thereby enhancing the plasticity of the material.

Abstract:Ni-based single crystal superalloys have excellent comprehensive properties at high temperature, and are widely used in hot-end components such as blades of aero-engines and gas turbines. Fatigue failure is one of the main failure modes of blades in service. Based on the research status of fatigue behavior of Ni-based single crystal superalloys, the fatigue damage mechanism of Ni-based single crystal superalloys was reviewed. The effects of crystal orientation, temperature and loading mode on fatigue behavior were discussed. The methods to optimize the fatigue life of Ni-based single crystal superalloys, such as composition optimization, heat treatment and surface treatment, were introduced. Finally, the application of some advanced testing techniques, such as in-situ testing, in the study of fatigue behavior of Ni-based single crystal superalloys was proposed, and the development trend of fatigue behavior research of Ni-based single crystal superalloys was prospected.

Abstract:As an important type of Al alloys with excellent comprehensive properties, Al-Mg alloys with good corrosion resistance and weldability are widely used in aerospace, rail transit and marine ships. The recent research progress on the microstructure and property regulation of Al-Mg alloys during solidification, heat treatment and plastic deformation is summarized, and the characteristic of each regulation method is analyzed. The application of continuous rheo-extrusion forming technique in the fabrication of Al-Mg alloys is emphatically introduced, and the future development direction of Al-Mg alloys is prospected.