The application, reviewing, assessment, and funding of the metallic materials (E01) discipline projects of the Department of Engineering and Materials Science of the National Natural Science Foundation of China (NSFC) in 2023 are statistically analyzed in this paper. The management on the progress, mid-term, and final examination of the E01 projects is introduced. The E01 discipline's efforts and actions to implement the science fund reform and to strengthen the talent training are expounded. In addition, the division's next-step work is also looked forward to.

As a form of damage caused by rolling contact, rolling contact fatigue (RCF) can lead to early pitting and flaking on the raceway surface of bearings, which is frequently accompanied by the propagation and fracture of RCF cracks. When the RCF crack is initiated on the raceway surface, large amount of stress, e.g., fluid pressurization, may be exerted close to the crack faces, which can not only accelerate the crack growth and cause rapid failure of the bearing but also lead to local microstructural alternations in the bearing steel. In this study, a needle-like structure was observed close to the cracks with flaking occurring during RCF in a GCr15 rolling bearing. The microstructures of the needle-like structure were analyzed via SEM, transmission Kikuchi diffraction (TKD), and TEM to elucidate its microstructural constitutions and characteristics. Results illustrated that the needle-like structure is a thin plate in three dimension decorated with some microvoids and equiaxed ferrite nanocrystalline formed at the interfaces. The formation of the needle-like structure was attributed to the local stress exerted close to the crack surface during the RCF of the bearings. This structure may be a type of decayed microstructure of the martensitic matrix of the bearing steel. With the increasing RCF stress cycles, the microvoids in the needle-like structure may facilitate the initiation and propagation of surface cracks preferentially, thus accelerating the occurrence of surface fatigue flaking in the bearing.

Austenitic stainless steels have wide applications due to their excellent properties, such as high strength, corrosion resistance, and superior workability. 304 stainless steel (304SS) is one of the most popular austenitic stainless steels. With a growing emphasis on healthcare, the antibacterial property of the materials becomes increasingly important. Ag is added to type 304 stainless steels to obtain an expected antibacterial property and reduce the occurrence of bacterial contamination. With the development of technology, previous research on Ag-bearing stainless steel was mainly concerned on its antibacterial properties, mechanical properties, and corrosion resistance. However, the microstructures of Ag-bearing stainless steels, especially the occurrence and distribution of Ag, have not been studied intensively. The present work studies the effects of Ag content on the microstructure, texture, and mechanical properties of austenitic stainless steel using OM, SEM, secondary ion mass spectrometer (SIMS), EBSD, and tensile test. SIMS analysis shows that Ag exists in austenitic stainless steel mainly in the form of Ag, Ag _x S, and Ag _x N compounds, which are mainly distributed at the grain boundaries and less within the grain. During recrystallization, the nucleation rate increases by the stimulation of coarse Ag, Ag _x S, and Ag _x N compound particles, while the grain growth is hindered by fine Ag, Ag _x S, and Ag _x N compound particles. Hence, the average grain size of 304, 304Ag-1, and 304Ag-2 stainless steel changes from (126 ± 3) μm to (47 ± 4) μm. The EBSD results show that the maximum pole densities of 304, 304Ag-1, and 304Ag-2 stainless steel samples are 3.24, 2.71, and 2.22, respectively, indicating that Ag can reduce the anisotropy of austenitic stainless steel. The yield strength and tensile strength of austenitic stainless steels decrease with the increase of Ag content, and the elongation increases with the increase of Ag content. Furthermore, strength and elongation consistency of Ag-bearing 304 stainless steel are much better compared to that of 304 steel at the angles of 0°, 45°, and 90° to rolling direction. The phenomenon of high Schmid factor grains surrounding low Schmid factor occurs in austenitic stainless steel, and the average Schmid factor of grains in {111} <110> slip system increases with the increase of Ag content, and the proportion of grains in “soft orientation” increases. Under the given loading stress, Ag-bearing austenitic stainless steel is more prone to deformation.

Researches have focused on the development of lightweight and high-performance steel materials to ensure automobile safety. Medium manganese steel is a potential candidate owing to its excellent mechanical properties and low production cost. However, the problem of plastic instability (Lüders strain, Portevin-Le Chatelier effect) is one of the main factors restricting the development of medium manganese steel. Therefore, resolving the plastic instability of medium manganese steel is a prerequisite for its development and hence to ensure the benefits of its mechanical qualities. Many studies have found that the stability of retained austenite is directly related to the plastic instability of medium manganese steel. In this work, cold rolled low-carbon medium manganese steel is selected, and multi-stable retained austenite is obtained by designing pretreatment and critical annealing process. The phase transformation of the retained austenite with different stability in each stage of the tensile process and its influence on the mechanical properties are studied. The results show that the microstructure containing pearlite + ferrite + martensite is obtained after pretreatment of medium manganese steel. After annealing, pearlite transformed into filmy retained austenite and ferrite phase; while martensite transformed into blocky retained austenite. Mn content in the filmy retained austenite is higher than that in the blocky retained austenite, making the filmy retained austenite more stable than the blocky one. The blocky retained austenite has poor stability, and phase transformation occurs at the initial stage of plastic deformation, eliminating Lüders strain. In contrast, the filmy retained austenite has high stability, and phase transformation occurs in the middle and late deformation, contributing toward its high strength and plasticity. The specimens containing double-stable retained austenite not only maintain the tensile strength (> 1000 MPa) and high fracture elongations (> 30%), but also have the characteristics of continuous yield and high strength yield ratio.

In general, Ni-based superalloys exhibit high strength, good oxidation and corrosion resistance, and good creep-resistant properties at high temperatures (HTs) because of the coherent precipitation of cuboidal γ′ nanoparticles into a fcc-γ matrix induced by co-alloying of multiple elements. The present work designed a series of Ni-based superalloys based on the cluster composition formula [Al-Ni₁₂](Al₁(Ti, Nb, Ta)_0.5(Cr, Mo, W)_1.5), with S1-CM (Cr_1.0Mo_0.5), S2-CW (Cr_1.0W_0.5), and S3-CMW (Cr_0.7Mo_0.4W_0.4), in which the amounts of Cr, Mo, and W were changed, whereas the contents of other elements were maintained. In addition, the effect of Cr, Mo, and W variation on the thermal stability of γ /γ′ coherent microstructure at HT in these superalloys was investigated. Alloy ingots were prepared by arc melting under an argon atmosphere, solid solutionized at 1300°C for 15 h, and then aged at 900°C for up to 500 h. Microstructural characterization and mechanical properties of these alloys in different aged states were studied by XRD, SEM, EPMA, TEM, Vickers hardness testing, and compressive testing.Result showed that all these three alloys have a high volume fraction (f > 70%) of γ′ particles uniformly distributed in the fcc-γ matrix. In particular, the γ′ particle shape is ellipsoidal in S1-CM and S2-CW alloys, whereas it is cuboidal in the S3-CMW alloy primarily because the latter has a more negative γ /γ′ lattice misfit (δ = -0.47%) than the former (δ = -0.25% to -0.33%). After aging for 500 h, the morphology of γ′ particles in each alloy has no evident change, and all of the particles have a slow coarsening rate (K = 10-18 nm³/s), in which the S3-CMW alloy exhibits the highest γ /γ′ microstructural stability (the coarsening rate of γ′ particles being K = 10.02 nm³/s). Moreover, the amount of second-phase precipitation near the grain boundaries in the S3-CMW alloy is less than that in the former two alloys. The microhardness test results showed that the microhardness of each alloy remains almost constant with aging time, thereby indicating the thermal stability of the coherent structure. In particular, the microhardness of the S3-CMW alloy is 397-418 HV, and the room-temperature compression yield strength is 818 MPa in the 200-h-aged state.

GH3536 alloy is a solid solution-strengthened superalloy for aero-engines. In general, this alloy is cold rolled into thin strips and used in honeycomb structures in engine sealing systems. During cold deformation of GH3536 alloy, a microstructural damage caused by carbide particles is the focus of attention. Therefore, understanding the influence of carbides on the cold deformation damage of GH3536 alloy is necessary to control such a phenomenon. Carbide cracking and local cracking of the matrix was observed through cold rolling deformation of thin strips and compression deformation of cylindrical specimens. Combined with finite element simulation results, the effect of carbide morphology and distribution characteristics on the microstructural damage was further discussed. Results show that when carbides are larger in size, irregular in shape, and distributed in agglomeration, the internal stress and fracture tendency are larger, which is contrary to small circular carbides. The agglomeration and banded distribution of carbides primarily increase matrix stress and cracking tendency. The heat treatment results show that the agglomeration and banded distribution characteristics of small carbides can be significantly improved by increasing the solution/annealing heat treatment temperature above 1150^oC, but the effect is not evident for large carbides above 10 μm.

Al-Mg series alloys are highly desirable for structural applications, owing to their high specific strength, good formability, and excellent corrosion resistance. However, high-strength Al-Mg alloys prepared via severe plastic deformation generally exhibit poor thermal stability, which is caused by the high-density grain boundaries (GBs). Achieving simultaneous high strength and thermal stability in binary Al-Mg alloys remains a challenge. In this study, Al-9Mg alloys with a combination of high strength (~597 MPa), decent elongation (~7.7%), and enhanced thermal stability were developed via cryogenic high-reduction hard-plate rolling (CHR-HPR). The effects of solute Mg content on the microstructure evolution and mechanical properties of CHR-HPR Al-Mg alloys were systematically investigated using EBSD, TEM, microhardness measurements, and tensile tests. The high yield strength is derived from high-density dislocations and low-angle GBs promoted via the high content of solute Mg atoms and low deformation temperature. In addition to the positive roles of Mg atoms and low deformation temperature on work-hardening ability, the simultaneous improvement in the ultimate tensile strength and ductility of CHR-HPR Al-Mg alloys with increasing solute Mg content is partially attributed to the enhanced work hardening induced via the dynamic strain aging. Furthermore, the recrystallization temperature of the CHR-HPR Al-Mg alloys gradually increased with increasing solute Mg content, and the recrystallization temperature of CHR-HPR Al-9Mg could reach 400^oC. The enhanced thermal stability of CHR-HPR Al-9Mg alloy is due to the high content Mg solute atoms, which strongly retard recovery and recrystallization by dragging dislocations and pinning GBs.

As a high-performance structural material, nickel-based superalloy has excellent comprehensive properties, such as high-temperature mechanical properties, thermal stability, and corrosion resistance. It is widely used in hot-end parts, including the combustion chamber, turbine blades, and turbine disks, among others. Due to severe working environments, oxidation has become a major life-limiting factor for the nickel-based superalloy. However, the high-temperature oxidation behavior of a superalloy is complex, related to many factors, such as chemical composition and preparation technology. Many advances have been achieved through improving alloy compositions to meet the anti-oxidation requirements, and others have been accomplished using major innovations in processing. As a new powder metallurgy technology, spark plasma sintering (SPS) has the advantages of a fast heating rate, low sintering temperature, and short sintering time. However, there are few studies on the oxidation behavior of alloys prepared by this technology. In this study, Ni20Cr-xAl alloys with Al content (mass fraction) of 1.5%, 3.0%, and 5.0% were prepared by mechanical alloying and SPS. Oxidation kinetics, XRD, SEM, and TEM were used to compare and investigate the isothermal oxidation behaviors of the SPSed and the as-cast alloys with the same composition in air at 900^oC. Results indicate that the SPSed alloys have uniform microstructures and fine grains, and abundant grain boundaries significantly accelerate the diffusion of elements. When the Al content is 1.5%, severe internal oxidation of Al occurs, and a Cr₂O₃ scale containing large pores and cracks is formed due to rapid external oxidation of Cr. Al₂O₃ particles dispersed in the alloy serve as nucleation sites for the exterior Al₂O₃ scale and have a pinning effect. However, when the Al content reaches 3.0% and 5.0%, a protective, continuous, and dense α-Al₂O₃ thin scale emerges. Therefore, both alloys display excellent oxidation resistance, the oxidation weight gain is 0.25 and 0.20 mg/cm², respectively, and the corresponding oxidation rate is 1.06 × 10^-7 and 4.92 × 10^-8 mg²/(cm⁴·s). Internal oxidation occurs in all the as-cast alloys, and no continuous external Al₂O₃ scale can be formed. The main component of the oxide scales is porous Cr₂O₃, which results in high oxidation rates and crack and spallation of the oxide scales.

MCrAlY-type coatings are widely applied to thermally loaded structures of aero-engines as standalone overlays and as a bond-coat for a thermal barrier coating system, owing to their good resistance to high-temperature oxidation and hot corrosion. The thermally grown oxide (TGO) formed at the interface is the primary factor affecting the durability of MCrAlY coatings, which is closely related to the coating method used. The coating performed by low-pressure plasma spraying (LPPS) has great adhesion, high deposition rate, and low internal oxidation. However, the prepared defects of rough surface and porosity adversely affect the antioxidant performance. High-current pulsed electron beam (HCPEB), as a powerful tool for surface modification of different materials, can normalize the defects, polish the coating surface, and reconstruct microstructures, which is crucial to promote steady growth of the protective TGO. Therefore, in this work, NiCrAlY coatings were prepared on the surface of a nickel-based superalloy via LPPS and then irradiated via HCPEB. The microstructural evolution, static oxidation performance at 1150^oC, and TGO residual stress distribution of NiCrAlY coatings before and after HCPEB modification were compared. The microstructural results show that the surface of the as-sprayed coating was rather rough and there were many unmelted large particles. After HCPEB irradiation, the surface of the irradiated coating was remelted, and became much flat and smooth. A rather dense and compact remelted layer approximately 12 μm in thickness was obtained. Furthermore, deformation structures and Y-Al enriched nanodispersed particles were introduced inside the remelted layer. The results of static oxidation and TGO residual stress show that after 150 h of oxidation, the oxide film formed on the as-sprayed coating fell off locally, accompanied by serious internal oxidation. Due to the cracking and peeling of the TGO, the internal stress was released. Conversely, the oxide film on the remelted surface of HCPEB irradiated coating grew steadily, and there was no trace of peeling, and the TGO stress increased steadily. The experimental results show that HCPEB is an effective and promising approach to drastically improve the high-temperature oxidation resistance of thermally sprayed MCrAlY coatings.

In some water-cooled nuclear power reactors, a hydrogenation-deoxygenation device is generally not used to simplify the system and save space, which can increase dissolved oxygen (DO) concentration in primary loop water. The increase in DO concentration will inevitably affect the corrosion resistance of zirconium alloy cladding materials. In particular, DO will accelerate the corrosion of Nb-containing zirconium alloys, and the corrosion rate of zirconium alloys with high Nb content is sensitive to DO concentration. In exploring the deterioration mechanism of the corrosion resistance of high-Nb-containing zirconium alloys in oxygen-containing steam, the corrosion behavior of the Zr-0.75Sn-0.35Fe-0.15Cr-1.0Nb (mass fraction, %) alloy was studied in superheated steam through deoxygenation, with 300 μg/kg of DO and 1000 μg/kg of DO at 400^oC and 10.3 MPa. The corrosion behavior was characterized by measuring the mass gain per unit area. SEM was used to observe the fracture morphology of the oxide film; TEM-EDS was used to observe and analyze the morphology, elemental distribution, and crystal structure of the alloy, second-phase particles (SPPs), and oxide film. The elemental distribution on the outer surface of the oxide film was analyzed by XPS, and the valence state of Nb was determined in accordance with the binding energy to analyze the influence of DO on the oxidation behavior of Nb in the oxide film. Results show that the corrosion resistance of the Zr-0.75Sn-0.35Fe-0.15Cr-1.0Nb alloy in superheated steam at 400^oC deteriorates with the increase of DO concentration. The deterioration mechanism of the corrosion resistance of the alloy in oxygen-containing steam is proposed. On the one hand, DO accelerates the oxidation of Nb in the oxide film and promotes the conversion of Nb²⁺ to Nb⁵⁺. On the other hand, DO promotes the oxidation of SPPs to m-Nb₂O₅ (monoclinic) and amorphous phase, thereby promoting the initiation and growth of cracks. These newly generated cracks provide more channels for the diffusion of O^2- and other oxidizing ions to accelerate the oxidation of SPPs near the cracks and the microstructural evolution of the oxide film, thereby accelerating the corrosion of the alloy.

With the rapid development of high-performance and high-energy-density lithium-ion batteries, lightweight current collector metal foils for lithium-ion batteries have become a crucial direction of industrial technological advancements. As the thickness of the current collector decreases, the fatigue failure problem becomes increasingly prominent. Once the fatigue failure of the current collector occurs, it will have a catastrophic impact on the electrochemical and safety performances of lithium-ion batteries. Here, to further clarify the fatigue damage mechanism of current collector foils, the high cycle fatigue strength and fatigue failure behavior of current collector Cu and Al foils for lithium-ion batteries under cyclic loading were experimentally investigated using tensile-tensile fatigue test and the EBSD technique. Results show that the fatigue cracks of the Cu foils mainly originate from the slip bands with larger grain sizes and propagate along the slip bands. Based on the microstructure observation and analysis of damaged grains, a statistical relationship between fatigue crack initiation and microstructure (grain size and its coefficient of variation, grain orientation, and Schmid factor (Ω)) of the Cu foils was obtained. Due to the presence of rolled defects on the surface of Al foils, the fatigue cracks are preferentially initiated at the surface defects. Extreme value statistics accurately predicted the possible defect population and the largest defect size in the Al foils, and the relationship between the defect size and fatigue limit was established using the Kitagawa-Takahashi diagram.

Titanium alloys have shown wide application potential in the areas such as aerospace and marine because of their comprehensive properties, including high specific strength, ductility, corrosion resistance, and damage tolerance. Given the rapid development of new-generation advanced military hardware toward large scale, high-speed, light-weight, and structure-complicated titanium alloys experience increasingly harsh application environments. Thus, developing novel high-strength and high-toughness titanium alloys is an important direction in the field of titanium research. To date, the compositional design of titanium alloys is performed within the framework of some empirical rules without involving strengthening and toughening mechanisms. This kind of approach can hardly achieve an accurate and efficient material design. Based on the abovementioned background, the effect of alloying on the precipitation strengthening of the α + β dual-phase titanium alloy was studied by using the first-principles exact muffin-tin orbital method in combination with a coherent potential approximation. High-strength and high-toughness titanium alloys obtain its high strength through precipitation strengthening in the β-phase matrix with α-phase precipitates. The influence of alloying on the precipitation strengthening is crucial to the understanding and prediction of alloy strength and rational alloy design. In the present work, the elastic moduli and lattice constants of a serial binary titanium alloy Ti-xM (M = Al, V, Cr, Mn, Fe, Co, Ni, Nb, Mo, Ta, W) against the composition x were calculated using the first-principles method. Based on which, the elastic moduli of the titanium alloy with a complex composition (such as Ti-Al-V and Ti55521) were evaluated using the concept of elastic Mo equivalency. Subsequently, the precipitation strengthening of binary titanium alloys and the Ti55521 alloy was evaluated by using the elastic modulus within the framework of the modulus strengthening model. Result shows that alloying elements, such as Co, Fe, W, Mo, Ni, and Mn, have the strongest precipitation strengthening effect for the same particle size and volume fraction of α precipitates, followed by Cr, Nb, and Ta, whereas V is the weakest. The strengthening effect increases with the content of alloying element. For the Ti55521 alloy prepared by using a thermal mechanical process, subsequent short-time aging weakens the precipitation strengthening effect compared with long-time aging.

Investment casting processes are controlled separately for its complex casting system, resulting in the dimensional out of tolerance. A calculation method for node displacement transfer is proposed based on the node normal vector and the nearest neighbor points in investment casting; the relationship between injection parameters, dimensional deviation in injected wax pattern, and casting solidification is studied, which provides a data model for digital twin. The digital twin is applied to the antideformation design and process optimization under a multiprocess for ring-to-ring casting. In the design stage, the geometric model of the mold cavity is designed via reverse deformation, and the error between the simulation results of the casting after the antideformation design and the target geometric is < 0.04 mm. In the casting, the optimal control of the subsequent process is performed according to the dimensional deviation of the previous process.

Spiral scanning mode, where ultrasonic probes relatively rotate forward around a tested bar, is commonly used in an automatic ultrasonic testing system for metal bar quality control. Current nondestructive testing standards for bars with ultrasonic technology specify that whether the bar is rejected or accepted should be made in accordance with the amplitude of the echo from a defect in the bar. The quality information obtained by the abovementioned standard testing procedure is only the echo from the defect, and it is too simple to characterize the defect in detail and accurately. Therefore, inspection using imagery and quantitative nondestructive testing (QNDT) of bar quality is the development trend of bar quality control technology in the future. In achieving QNDT of metal round bars, a synthetic aperture focusing on imaging algorithm in a polar coordinate system (pSAFT) and its surrounding scan-mode time-domain synthetic aperture focusing technology (ST-SAFT) were proposed in accordance with the classical ultrasonic synthetic aperture focusing technology (SAFT) theory on a Cartesian coordinate system. Based on the signal set collected by the spiral scanning automatic detection system, the formula of time-delay superposition imaging expressed by the effective synthetic aperture radian was deduced to image the defects in the bar with a cross-sectional view. By preparing a transverse-hole artificial defect sample for the testing experiment, ultrasonic testing data were processed by ST-SAFT, and then a circular section tomography was imaged. Image edge recognition was used to quantitatively evaluate the sizing ability and positioning resolution of ST-SAFT for defect detection. Experimental results show that the measured value of artificial defects with ST-SAFT is equivalent to the real value; the positioning of the transverse side-drilled hole is accurate, and the imaging resolution is significantly better than that of B-scan. The imaging speed for each circular section can reach the order of milliseconds, which can match the mechanical scanning speed of bar inspection for one circle. Therefore, this technology can be used to improve the technical level of ultrasonic automatic testing equipment for metal round bars and ensure safety of the application of metal round bars.