In this paper, the basic principle of first principles in material calculation is briefly introduced, and its progress in the research of superconducting materials, especially in the field of superconductivity, is summarized, which provides theoretical support for the further development of new superconducting materials and their practi‐ cal application; The shortcomings and suggestions of first principles calculation in the field of superconducting materials are put forward, and its research prospect in the mechanism of superconducting principles is prospected.

Bayan obo iron ore, coexisting with multiple valuable minerals such as iron and rare earth elements, ex‐ hibits high reactivity, abundant resources, and low cost. By employing the calcination synthesis method, a mixture of this ore with copper oxide is prepared into a spinel CuFe2O4 oxygen carrier, aiming to develop a performance-op‐ timized, cost-effective, and environmentally friendly oxygen carrier for chemical looping combustion. The reduc‐ ibility and cyclic stability of the oxygen carrier were investigated through thermogravimetric analysis and small fixed-bed experiments, complemented by XRD characterization for an in-depth analysis of reaction characteristics and mechanisms. The results demonstrate that the addition of copper significantly enhances the activity of the iron concentrate oxygen carrier, improves the high-temperature resistance and anti-sintering stability of the copper ox‐ ide oxygen carrier, and forms a more stable spinel structure of CuFe₂O₄, exhibiting excellent synergistic effects. The CO program warming test illustrated that the reduction reaction of the copper-iron composite oxygen carrier primarily involves CuFe₂O₄, proceeding in three stages: in the first stage, CuFe₂O₄ is reduced to Cu and Fe₃O₄ at low temperatures with the highest reactivity; the second and third stages involve the reduction of Fe₃O₄ to FeO and then FeO to Fe, respectively. During 26 reduction-oxidation cycles, the CuFe900 oxygen carrier displayed no sig‐ nificant sintering, maintaining good reactivity and cyclic stability.

Compared with traditional alloys, high entropy alloys possess excellent mechanical properties, which have become a hot spot in recent years. Refractory high entropy alloy is mainly composed of refractory metal elements, which has high strength and high temperature resistance, so it has great potential for application in extreme environment. However, there are still some problems such as strength-plastic mismatch and poor processability in refractory high entropy alloys. It is the focus of research to regulate the microstructure of refractory high entropy alloys then improve strength and plasticity. In this paper, the preparation methods of refractory high entropy alloys were compared, the effects of regulating metal and nonmetal elements on microstructure and mechanical properties of refractory high entropy alloys were discussed. At the same time, the functions of thermal machining on mechanical properties of refractory high entropy alloys were investigated.

Al-Si-Cu-Ni gradient-structured alloys were prepared under different process parameters by varying the laser power during selective laser melting and forming, and the bending properties were tested under positive and negative pressure conditions. After optimizing the process parameters, the comprehensive mechanical properties of the gradient-structured alloys were improved, the microstructures at different locations on the sides were observed, and the hardness distribution was tested. The results show that the bending properties under positive pressure conditions are better than those under counterpressure. With the increase of laser power, the microstructure is gradually coarsened, the precipitation amount of Cu-rich and Ni second phases increases, and the Vickers hardness and Brinell hardness linearly decrease, which makes the alloy samples produce a gradient structure. The bending strength and fracture displacement of the gradient-structured alloys prepared under the optimal process parameters under positive pressure can reach (838±22) MPa and (0.93±0.04) mm, which are significantly higher than those of the homogeneous structure alloys ((767±24) MPa, (0.85±0.03) mm), indicating that the gradient structure produces a toughening effect on the alloy materials, which is mainly attributed to the high strength of the fine-crystalline tissues, good plasticity of the coarse-crystalline tissues, and good plasticity of the coarse-crystalline tissues. The synergistic effect of the gradient structure on the alloys is mainly attributed to the high strength of the fine-crystalline tissue and the good plasticity of the coarse-crystalline tissue.

The main ironmaking processes in China are blast furnace ironmaking and smelting reduction, both of which are high temperature metallurgical processes with high energy consumption, while the gas-based reduction method with low smelting temperature is difficult to develop due to the limitation of domestic natural gas resourc‐ es. The coal-based direct reduction method develops slowly due to high energy consumption and low productivity. In order to reduce its energy consumption and reduction cost, in this paper, the reduction mechanism between different iron ore powder and coal powder is studied by differential thermal analysis experiment. Through the dif‐ ferential thermal analysis of coal powder with different proportions of iron ore powder, the best method of direct reduction temperature of iron ore powder is expected to be found. The results show that PB powder ore relative to vanadium and titanium iron ore reduction process in the consumption of coal powder less coal ratio is lower, but the maximum heat absorption is slightly higher than the two vanadium and titanium iron ore powder. When PB powder and anthracite are selected, and the ratio of carbon to oxygen is 1.25, namely, the carbon content is 24.45% of the mass of iron ore powder, the reaction temperature of iron ore powder reduction is the lowest. At this time, the initial reaction temperature is 1 025 °C, and the violent reaction temperature is 1 210 °C.

Porous nickel plates with porosity of 22.2%-52.4% were prepared by powder rolling technology using ammonium bicarbonate（NH4HCO3）as pore-making agent. The effect of pore-forming agent content on microstructure and properties of porous nickel plate was studied. The results show that with the increase of pore-forming agent content, the porosity of porous nickel plate increases gradually, the relative permeability increases gradually, and the tensile strength decreases gradually. When the content of pore-forming agent is 20%, the porosity of porous nickel plate is 40.7%, the relative permeability coefficient is 10.79 m3/(h·kPa·m2), and the tensile strength is 135 MPa. When the content of pore-forming agent is 40%, the porosity of porous nickel plate is 52.4%, the relative permeability coefficient is 41.0 m3/(h·kPa·m2), and the tensile strength is reduced to 51 MPa.

As a new generation of kinetic energy armor-piercing projectile materials, the preparation of 90W-Ni- Mn alloy has the problems of high W-W contiguity, low sintering density and high processing cost. In order to solve these problems, the tungsten powder is treated with electroless nickel plating, and take shape using the feedstock by injection molding process, and then cooperate with the self-developed new argon-argon hydrogen twostep sintering process to prepare a 90W-6Ni-4Mn alloy with low W-W contiguity. Experiments show that 90W-6Ni- 4Mn alloy can be nearly net shaped, and the new sintering process can not only reduce W and Ni oxides content, but also avoid the generation of MnO. The relative density of the prepared sample reaches as high as 99.2%, the bonding phase distribution is uniform, and the W-W contiguity is low. Through microstructure and fracture morphology analysis, it is found that electroless nickel plating can promote the activation and sintering of tungsten skeleton, improving the density of alloy and promoting the uniform distribution of bonded phases. The 90W-6Ni-4Mn alloy as made with low W-W contiguity slows down the failure rate due to the reduction of the weak interface of WW, resulting in the compressive strength and tensile strength are as high as 1 583.4 MPa and 968 MPa, and the well plasticity and toughness of 21.5% and 5.3 J/cm2, respectively.

The technology of producing ultra-fine iron powder by hydrogen reduction is studied, using iron oxide red of pickling waste in steel works as raw material, the cost is less than one third of the cost of producing ultrafine iron powder by carbonyl method. The properties of the products are TFe≥98.5% , loose density is 0.80~1.20 g/cm3, free grain size D50≤16.5 μm, specific surface area is more than 2.10 m2/g. It is widely used in ultra-hard diamond tools, powder metallurgy injection molding materials, high-specification soft magnetic materials, adsorption materials, aerospace materials, food and other fields.

In order to study the radiation resistance of FeCrAl ODS steel, the evolution of dislocation loops in Fe‐ CrAl ODS steel under irradiation was studied using in-situ ion irradiation method, and the irradiation hardening effect of FeCrAl ODS steel was characterized using nanohardness. The research results indicate that after ion irradiation, FeCrAl ODS steel produces<100>and 1/2<111>dislocation loops, and the average diameter and density of dislocation loops increase with the increase of irradiation damage dose. As the irradiation temperature increases, the growth rate of dislocation loops increases while the number density decreases. After 10 dpa ion irradiation, the irradiation hardening value of FeCrAl ODS steel is only 0.35 GPa, indicating good resistance to irradiation hardening.

W-Cu composites is a structural and functional integrated material composed of W and Cu, exhibiting exceptional properties such as high hardness, strength, thermal stability, wear resistance, low coefficient of thermal expansion, good ablative resistance and conductivity. It finds extensive applications in electronic, electrical, aerospace and military industries. However, commercial W-Cu composites prepared through high temperature infiltration or liquid phase sintering often possess coarse structures with inferior mechanical properties. As China's industrial modernization progresses rapidly, higher requirements are also put forward for the comprehensive properties of W-Cu composites. As a result, the preparation technology of W-Cu powder and blocks has greatly accelerated the development of W-Cu composites in recent years. This review summarizes the mechanisms and characteristics of different forming technologies and powder preparation techniques for W-Cu composites, along with an analysis of their microstructure and properties. Finally, future trends for the development of W-Cu composites are discussed.

This paper describes a production process for the preparation of H13 alloy special powders by plasma rotating electrode atomization (PREP), including raw material preparation, atomization, and powder grading. The morphology, particle size, composition, fluidity and bulk density of the powder were tested by using scanning electron microscope, particle size analyzer, nitrogen-sulfur meter, ICP, Hall flow meter and bulk density meter. And a comparison was made with the powder produced by a domestic company using aerosolization (AA). The result shows that the surface quality of H13 alloy powder produced by PREP is excellent, with high powder sphericity, clean surface and almost no satellite powder, adhesive powder and hollow powder. The surface morphology is mainly fine dendritic organization with uniform organization. The physical properties of the powder are excellent, with high bulk density (4.6 g/cm3) and good flowability (12.8 s/50g). The particle size of the powder is centrally distributed, and the yield of the powder of specific size is high. However, the yield of fine powder is not high, and further optimization of the process is needed. The surface quality of H13 alloy powder prepared by AA is poor, with more satellite powder, shaped powder and adherent powder, and more surface defects. In addition, the physical properties are poor, and the fluidity and bulk density are not as good as the requirements of powder products.

Nickel-based superalloy strengthened by γ′ phase (L12 structure) has excellent high temperature strength, great plasticity and outstanding damage tolerance. These properties make it irreplaceable in many areas, such as aerospace industry and nuclear power industry. Meanwhile, a series of problems such as segregation, inhomogeneity and poor hot working performance coming from traditional casting/forging superalloy have been solved by powder metallurgy process. Nowadays, powder superalloy has become the first choice of key hot end components such as turbine disc of advanced aero-engine and powder superalloy has become an important symbol of engine advancement. To obtain desired mechanical properties, superalloy is usually fabricated by extrusion, hot forging and other processes. Therefore, it is of great importance to study the hot deformation behavior of superalloy. To study the hot deformation behavior of superalloy, constitutive model is applied to describe the relationship between flow stress and deformation parameters. Among many constitutive models, Arrhenius-type constitutive model is widely and commonly used in describing deformation behavior of nickel-based superalloy. Through the regression analysis, the relationship between flow stress and strain rate, deformation temperature is established and deformation parameters can be optimized to acquire superalloy with homogeneous microstructure and excellent mechanical properties. However, because of the complex none-linear characteristics of deformation parameters on flow stress, it is difficult to predict the flow behavior precisely. Thus, tools to describe this relationship more accurately are urgently needed. Deep learning tools, such as artificial neural network (ANN), is the promising way to solve this problem. ANN has the ability of self-learning, self-adaptation, strong nonlinear function approximation and fault tolerance. Meanwhile it does not rely on mathematical models and deformation mechanisms. Through the adjustment of the internal connections between a large number of nodes, ANN can achieve the purpose of information processing and predict more accurate than other constitutive models. The effect of deformation temperature and strain rate on hot deformation behavior of the PM superalloy was investigated. The change in flow stress during hot deformation actually is the competition between work hardening (dislocation accumulation, dislocation interaction, etc.) and softening mechanism (DRV, nucleation, grain growth, etc.). The AARE and R of typical Arrhenius-type model is as large as 23.36% and 0.965 8. After the modification in strain, the AARE and R drops to 9.92% and 0.988 7, respectively. While BP-ANN model is adopted, the value of AARE and R slumps to 1.75% and 0.999 5. BP-ANN performs better in dealing with the complex relationship between deformation parameter and flow stress.

The friction pairs in wet clutches can cause drag torque and associated energy loss, when friction discs are not engaged, due to the viscous fluid nature of the lubricant subjected to relative motion between the friction pairs. This phenomenon is detrimental to the service life of wet clutches and causes concern of risk. In addressing this issue, based on the Navier-Stokes equation, a total of 12 groove designs with 24 configurations are designed and analyzed by means of finite element numerical simulation to explore the methods of reducing the drag torque and energy loss. The results show that the combination of spiral groove and radial non-slot design has good cooling effect and high dynamic friction coefficient. This paper provides an important reference for the design of friction pairs oil grooves, which is of great significance for guidance.

Titanium and titanium alloys have been widely studied and applied as biomedical metal materials. In order to better satisfy the requirements of low elastic modulus, biological activity after implantation in human body, the preparation of titanium based hydroxyapatite (HA) biological composites by adding hydroxyapatite with powder metallurgy has become a research hotspot. Based on the basic properties and existing problems of titanium and titanium alloys, this paper summarizes the research progress of titanium based HA biological composites by powder metallurgy such as hot pressing, powder injection molding, spark plasma sintering from the aspects of preparing biological composites to reduce elastic modulus, improve biological activity and corrosion resistance. The representative cases were listed separately which were preparation for titanium hydroxyapatite biocomposites by synthesis of α type, α+β type and β type titanium alloy with HA. Moreover, the challenges faced and suggestions for the development direction are also proposed.

TC11 titanium alloy samples were formed by selective laser melting technology, the effects of laser power (220-260 W) and exposure time (45-55 μs) on the microstructure and mechanical properties of the samples were studied. The results show that the laser power and exposure time mainly affect the laser power density during the forming process, resulting in differences in microstructure and mechanical properties：when the laser power density increases, the liquid retention time is relatively long, the cooling rate is relatively low, the columnar crystal size is relatively large, and the martensite lath size increases; When the exposure time is 50 μs and the laser power is increased to 260 W, the microhardness of SLM forming specimen increases to 437 HV0.3, the tensile strength increases to 1 463 MPa, and the elongation after fracture decreases to 6.0%; When the laser power is 200W and the exposure time is increased to 55 μs, the microhardness of SLM formed specimen increases to 404.2 HV0.3, the tensile strength increases to 1 446 MPa, and the elongation after fracture decreases to 4.8%. When the laser power is 220 W and the exposure time is 50 μs, TC11 titanium alloy with better matching strength and plasticity can be obtained, and its tensile strength and elongation after fracture are 1 345 MPa and 10.6% respectively.

Aiming at the phenomenon of abnormal ablation on the surface of W-7Cu infiltrated with tungsten and copper, samples were taken from the rudder surface and guard plate of returned part, and the ablative characteristics, microstructure, surface debris, fracture morphology and metallographic structure of samples were compared and analyzed. The results showed that rudder surface’s ablation was more sever, both propellant residue on the surfaces were distributed, the fracture apperance was dominated by transgranular and intergranular fracture, no abnormal tissue was found; According to the results of metallographic and transmission electron microscope, the cavity of rudder surface is more than that of the guard plate, and copper leaks exist in both areas, energy spectrum analysis showed that the copper content has different gradients, the copper precipitation at rudder surface was significant that affected by three kinds of working conditions including temperature, time and scour speed. The study conclusions can provide a basis for subsequent failure analysis and quality control of tungsten-impregnated copper gas rudder products.

Nb-16Si-10Mo and Nb-16Si-10Mo-10Ti alloys were prepared by Spark Plasma Sintering (SPS) technique. The effect of sintering temperature on the microstructure and properties of the two alloys was analyzed . The results show that Nb-16Si-10Mo alloy is composed of three phases: Nbss, Nb3Si and Nb5Si3, while Nb-16Si10Mo-10Ti alloy is composed of three phases: Nbss, Nb5Si3 and Tiss, and the densities of both alloys are above 99.4%. With the increase of sintering temperature, the Vickers hardness and compressive strength of the two alloys first increase and then decrease, while the bending strength and fracture toughness gradually decrease. With the addition of Ti element, the fracture morphology appears dimple characteristics, and the fracture mode changes from brittle fracture to composite fracture, and the Vickers hardness and compressive strength of the alloy are reduced at various sintering temperatures, while the bending strength and fracture toughness are increased.

Aluminium-based metal matrix composites were synthesized from Al、TiO2 and Gr powder mixtures using the powder metallurgy technique and their forming characteristics were studied during cold upsetting. The powder preforms were pressed with a 40 kN hydraulic press with appropriate punches and dies, and then sintered in an electric furnace at 590 ℃ for 3 h in an air atmosphere. The sintered preforms were subjected to incremental compressive loads of 10 kN until cracks were found on the free surface. Axial stress (σz), hoop stress (σθ), mean stress (σm) and effective stress (σeff) were calculated for all pre‐ forms, which are related to the axial strain (εz).The densification behavior of the composites under axial strain (εz)and transverse strain was investigated.It is observed that the addition of 5% TiO2 into the Al matrix increases σz, σθ, and σm. The addition of both TiO2 and Gr reinforcements reduces the densification and deformation characteristics of the sintered preforms during cold upsetting.

Fe3Al porous metal filter element is especially suitable for precision filtration and gas-solid separation under high-temperature high-pressure and corrosive environment. In order to meet the usage requirements of the filter element, in addition to considering its pore characteristics, its mechanical properties are also crucial. Fe3Al intermetallic compounds porous materials were prepared by powder metallurgy technology in this paper. The effects of ambient temperature on the pore characteristics, , mechanical properties and microstructure of the porous materials were studied by XRD, SEM, pore structure and mechanical properties. It shall provide a reliable basis for the use of Fe3Al porous materials at high temperature. The experimental results show that Fe3Al porous materials have good tensile strength and permeability properties at medium and high temperature. The tensile strength reaches the maximum at 300 ℃ and then decreases with the increase of temperature, and decreases obviously when the temperature is higher than 700 ℃. The fracture belongs to brittle fracture. The order degree of the Fe3Al intermetallic compounds porous materials changes with the increase of temperature.

Ti/ZrO2-Al2O3 gradient material was prepared by laser directed energy deposition technology. The microstructure, element distribution and changes of microhardness were systematically analyzed by means of scanning electron microscopy, energy spectrometer and Vickers hardness tester, and the influence of Al2O3 con‐ tent in ZrO2 ceramic powder on the microstructure and properties of the material was explored. The results show that with the increase of Al2O3 content, the mixing of the two phases is more uniform, while the cracking phenom‐ enon is more serious at the interface. The hardness of ceramic region in the sample also increases as the Al2O3 content increases. When the Al2O3 content is 30%, the hardness reaches 1344.5HV0.2, but in the binding region, the hardness increases significantly, reaching 1187.3HV0.2, only when the Al2O3 content increases to 30%.

The coercivity of sintered Nd-Fe-B magnets can be improved and the cost can be reduced when light rare earth is used as the diffusion source to replace part of heavy rare earth. In this paper, the heavy rare earth Tb in Tb-Al-Ga alloy was partially replaced by low-cost light rare earth Pr. The effects of Pr substitution on the magnetic properties and microstructure of sintered dual-main-phase Nd-Ce-Fe-B magnets and sintered singlemain-phase Nd-Fe-B magnets were studied, and the coercivity strengthening mechanism was revealed. With Pr60Tb20Al10Ga10 as the diffusion source, the coercivity of the grain boundary diffusion magnet increases obviously. Compared with the single main phase magnet, the diffusion depth of the double main phase magnet is significantly increased. Pr with low melting point preferentially enters the magnet and improves the wettability of grain boundary phase. This causes more Tb elements to enter more deeply in magnet, forming a shell structure with high magneto-crystalline anisotropy field surrounding main phase grain, and then improving the coercivity of GBDed magnet.

Rare-earth permanent magnet radiation-oriented integral magnetic rings are a crucial type of permanent magnet material, widely utilized in high-end electromechanical products, precision measuring instruments, and advanced defense technologies, among other fields. The advancement of radial integral permanent magnet ring preparation technology is of significant importance for promoting the leapfrog development of China's advanced equipment. This article introduces the classification and characteristics of rare earth integral permanent magnetic rings from three aspects: magnetic ring materials, preparation processes, and orientation methods. It focuses on the current research progress of the radial forming process and mechanical properties of sintered rare earth radial integral permanent magnetic rings. These advancements provide new ideas for the development of high-performance sintered rare earth radial ring technology.

Powder metallurgy technology is a scientific technology manufacturing metal powders, alloy powders, non-metallic powders, compound powders, or materials or products made from these powders through forming and sintering. As the metal powder in the preparation process is easy to adsorb oxygen and oxidation, in the sintering process is not easy to fully deoxidise, and with the development and use of alloying elements, chemically active alloying elements are easy to combine with oxygen elements, increasing the difficulty of deoxidisation, so that powder metallurgy materials are prone to oxygen content exceeding the standard, which seriously affects the performance of powder metallurgy materials. This paper discusses the influence of oxygen content on the preparation process and mechanical properties of various metals and alloys, and introduces the methods of controlling the oxygen content of some metals in the powder metallurgy process. It focuses on the research progress of oxygen content control of iron-based powder metallurgical materials, titanium and titanium alloy powder metallurgical materials, copper alloys, refractory metal tungsten and molybdenum powder metallurgical materials, and summarises the current status of the research and looks forward to the development trend of its future.

In this study, the CoFeNiCrNb0.5 high entropy alloy cladding layer was fabricated on the surface of 316L stainless steel by plasma cladding technology. The microstructure, phase composition, element distribution and wear resistance of the cladding layer of CoFeNiCrNb0.5 high entropy alloy were studied. The results show that the phase composition of the cladding layer of CoFeNiCrNb0.5 high entropy alloy is composed of FCC phase and Laves phase with face-centered cubic structure. Among them, the FCC phase is the matrix phase, and the Laves phase is formed at the interdendrite. The microhardness of the cladding layer of the CoFeNiCrNb0.5 high entropy alloy is about（510.5±14.2）HV, which is about 2.1 times that of the 316L matrix. The higher hardness of the cladding layer is mainly caused by the solid solution strengthening of Nb element and the diffusion strengthening of Laves phase. In addition, the CoFeNiCrNb0.5 high entropy alloy cladding layer has excellent wear resistance, and the specific wear rate is about 5.9×10-6 mm3/N·m, which is significantly better than the stainless steel substrate. Abrasive wear is the main wear mechanism of CoFeNiCrNb0.5 high entropy alloy cladding layer.

Based on coprecipitation, in this paper, the effects of feeding sequence, feeding position, feeding tube number and feeding temperature of nickel-cobalt-manganese sulfate solution, alkali solution and ammonia solution on Ni0.55Co0.5Mn0.40(OH)2 were studied. The results show that Ni0.55Co0.5Mn0.40(OH)2 with high performance can be synthesized through method that Ni-Co-Mn liquid, ammonia liquid and alkali liquid as feeding sequence, Ni-Co- Mn liquid is fed up, alkali-ammonia liquid is fed down, Ni-Co-Mn liquid and alkali liquid are fed two points and 40-45 ℃ feeding temperature of Ni-Co-Mn solution.

In order to study the influence of Nb elements on the organization and properties of FeCoCrNiMn high-entropy alloy, FeCoCrNiMnNb high-entropy alloy coatings were prepared on the surface of Q235 steel by using laser cladding technology, and the phase compositions, microstructures, elemental distributions, nano-hardnesses and wear behaviors of the coatings were investigated, respectively. The results show that the FeCoCrNiMnNb high-entropy alloy coating consists of FCC phase and Laves phase. Among them, the matrix phase is the FCC phase and the bar organization is the Laves phase. Due to the solid solution strengthening and the second precipitation strengthening effect, the nanohardness of the FeCoCrNiMnNb high-entropy alloy coating is significantly enhanced to about 9.193 GPa, which is about twice of that of the FeCoCrNiMn coating. Due to the significant enhancement of the nanohardness, the FeCoCrNiMnNb coating has excellent wear resistance, with a wear rate of 2.549×10-5 mm3/N·m, which is about 0.33 times that of the FeCoCrNiMn coating. The wear mechanism of the FeCoCrNiMnNb coating is a single abrasive wear. In summary, the FeCoCrNiMnNb high-entropy alloy coating has very high nanohardness and excellent wear resistance

Based on the linear reciprocating in-situ observation tester, the effects of powder layer thickness on interface wear condition, friction characteristics and real contact area ratio in 30 strokes were analyzed. The results show that thickness of powder layer is 1.5 μm, the powder layer is relatively thin on the surface of specimen. Asperities in some areas is initially exposed, and powder lubrication film is not formed. Main load is the contact load of asperities and serious wear marks appear. The initial real contact area ratio is 11.17% and finally decreases to 20.14%. The powder layer is 4.5 μm that the good lubrication film is formed in the area completely covered by the powder layer, and finally the lubrication film is completely peeling off and load is reduced. The powder layer is 6μm that powder layer completely covers the contact area and form complete lubrication film, load of powder layer is dominant and there is no scratch. Load first increases to 6 N and then decreases to 2 N, and asperities bearing capacity 2 N accounts for 33% of the total load. Friction ratio of powder layer is more than 73.3% and the real contact area ratio remains above 60%. The results shows that powder layer thickness is 6 μm that the powder has good flatness, high carbon content, full contact and good lubrication.

The selective laser melting forming system based on PLC control was used for rapid forming of Al-Mg- Mn alloy. The effects of laser scanning speed on the density, microstructure, phase and hardness of the formed parts were studied, and the effects of aging temperature and time on the compression properties of the formed parts were investigated. The results show that with the laser scanning speed increasing from 700 mm/s to 1 300 mm/s, the porosity of the formed sample increases and the relative density decreases gradually under the condition of other process parameters unchanged. With the increase of laser scanning speed, the weld pool parallel to the deposition direction gradually increases, and the fusion line becomes thinner. Multilayer deposition channels with cross distribution can be seen perpendicular to the deposition direction, but when the laser scanning speed is 1300mm/s, the weld channel contour is relatively vague; At the same laser scanning speed, the hardness of the plane parallel to the deposition direction is higher than that of the plane perpendicular to the deposition direction. With the increase of laser scanning speed, the microhardness of XZ plane and XY plane first increases and then decreases, and the maximum hardness is obtained when the laser scanning speed is 900mm/s; With the increase of aging temperature or the extension of aging time, the microhardness, yield strength and compressive strength of the selective laser melting forming sample first increase and then decrease, and the maximum value is obtained when the aging temperature is 300 ℃ and the aging time is 6 h, which is mainly related to the precipitation strengthening effect of Al3(Sc,Zr) phase in the alloy at this time.

TC4 titanium alloys with high density, fine grain and excellent tensile properties were prepared by hot pressing (HP) sintering technique. The effects of HP sintering temperatures (880, 930, 980 ℃) on the microstructure and tensile properties of TC4 titanium alloy samples were investigated by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), room temperature tensile tests, etc. The results show that the HPed TC4 samples consist mainly of equiaxed α phase and intergranular β phase. With the increase of hot pressing temperature, the grain coarsens, and the volume fraction of the α phase decreases. When HP temperature is 930 ℃, the tensile properties of the alloy sample are the best at room temperature, and the maximum tensile strength and elongation after fracture are 934 MPa and 26.3%, respectively, which is better than the cast and hot isostatic pressing TC4 titanium alloys reported in the relevant literature.

Mg10Ni-X alloys (X=MWCNTs, TiF3, MWCNTs-TiF3) were prepared by high-energy ball milling, the effects of MWCNTs/TiF3 catalysts added alone and MWCNTs TiF3 catalysts added together on the particle morphology, phase composition and activation behavior of Mg10Ni alloys were studied. The results show that the particle size of Mg10Ni-X alloy after high-energy ball milling treatment reduces in varying degrees by adding catalyst to Mg10Ni alloy. Compared with TiF3 catalyst, MWCNTs catalyst has better particle refining effect, and the particle refining effect of composite addition of MWCNTs-TiF3 catalyst is the best. After high-energy ball milling of Mg10Ni-MWCNTs-TiF3 alloy with MWCNTs-TiF3 catalyst, the microstructures of TiF3 and MWCNTs have not changed. The order of Mg2Ni phase content and Mg2Ni phase cell volume in the alloy from large to small is: Mg10Ni-MWCNTs-TiF3>Mg10Ni-MWCNTs>Mg10Ni-TiF3>Mg10Ni. The activation performance of the alloy improves in varying degrees after the addition of MWCNTs and TiF3 catalysts, the improvement effect of TiF3 catalyst on the activation performance is better than MWCNTs, and the activation performance of the alloy after adding MWCNTs-TiF3 catalyst is the best.

The spherical molybdenum and molybdenum alloy TZM powders were prepared by plasma rotary electrode atomization technology, and the particle size distribution, oxygen content, micromorphism and surface tissue of tungsten powder were characterized by laser particle size analyzer, O-N analyzer, scanning electron microscope (SEM). The results show that the oxygen increments of both powders are under 50×10-6, the powder particle size is concentrated in a single-peak distribution of 45-150 μm. Because of the smaller surface tension of TZM, which has a smaller median particle size than Mo powder, and the powder has high surface quality and better process performance, which provides theoretical support for the evaluation of palladium and vanadium alloy powder for additive manufacturing.

Compared with laser and e-beam based additive manufacturing technologies, the combined 3D printing and sintering process is cheaper, but the exploration of the process parameters in the sintering stage is not comprehensive and in-depth enough. Therefore, the experiment uses screw-based 3D printing technology to prepare 17-4PH stainless steel samples, to explore the influence law of sintering process parameters (sintering temperature, heating rate and holding time) on the properties of 17-4PH stainless steel, including porosity and tensile property measurements, and to investigate the influence law of the sintering process parameters on the pore structure, microstructure and fracture morphology. The changes in the mechanical properties of the sintered samples were elaborated through the changes in the pore structure, microstructure and fracture morphology. The results show that the mechanical properties of the sintered samples are best when the sintered samples are heated up to 1 360 ℃ for 1 h at a rate of 4 ℃/min, with a yield strength of 518 MPa and a tensile strength of 693 MPa.

Selective laser melting (SLM) technology has attracted much attention from the aeronautics and astronautics realm due to its advantage of high degree of freedom, high accuracy, and good mechanical properties after printing. Considering the durability and designing concept of damage tolerance of structural materials, the crack propagation rate of components applied into aeronautics is regarded as one of the key points to ensure the service safety of equipment. The research of ameliorating the crack resistance of titanium alloys through posttreatment is believed to provide valuable data guidance to the further application of SLM-printed titanium-based components in the aeronautics. In the current paper, the hot isostatic pressing (HIP) process is conducted to SLM-printed TA15 alloys as the post-treatment. Specifically, the influence of the HIP temperature on the microstructure, hardness, and crack propagation rate are investigated in details. The microstructure of the as-printed TA15 alloy HIP treated at the temperature range of 900-980 ℃ is generally identified as multi-hierarchical needle or lath-like α phase. Besides, the size of the α phase gradually coarsens along with the rise of the HIP temperature. The average length of primary α phase ranges from 60 μm to 66 μm. Whereas, the width of primary αphase significantly increases from 2.35 μm to 5.62 μm. The hardness of the HIPed specimen resultantly reduces from 35.8 to 31.9 (HRC). When the HIP temperature surpasses the phase transformation point of α to β phase, the formation of Widmannstatten structure is observed in the specimen with hardness of 32.2 (HRC). The crack propagation rate of the specimens HIP treated utilizing different parameters converges and is seldomly affected by the microstructure when the stress intensity factor range (ΔK) is within 20~50 MPa·m1/2. While the crack propagation rate gradually decreases with the rise of HIP temperature when ΔK＜20 MPa·m1/2. Coarsening of multi-hierarchical needle(lath)-like α phase enhances the deflection of crack propagation path caused by microstructure, which correspondingly retards the further propagation of cracks. Widmannstatten structure formed in the specimen HIP treated at 1 020 ℃ possesses the lowest crack propagation rate among different microstructures. In addition, the packets of α phase with various crystallographic orientation inside the β phase favors the conversion of fatigue cracks propagation path, which effectively lengthens the propagation path and reduces the crack propagation rate. In summary, the coarsened multi-hierarchical lath-like α phase in the specimen HIP treated at 980 ℃ and the Widmannstatten structure formed after HIP treatment at 1 020 ℃ benefit to the reduction of crack propagation rate. While the hardness of specimens suffers a certain loss.

The phenomenon of rotary kiln ring seriously affects the quality of reducing materials and will reduce production efficiency, so it is necessary to explore the mechanism of powder reduction rotary kiln ring and take certain measures to alleviate this phenomenon. PB powder and anthracite were selected as the raw materials, the products reacted with refractory bricks that have Al2O3 and SiO2 as the main components, and the microstructure of different temperatures, carbon formulations and lower rings of materials were characterized by scanning electron microscopy-energy spectrum analysis. The results show that with the increase of temperature, the structure of the ring sample become tighter, the number of stomata and pore size decrease, and the white filamentous structure gradually appeares in the ring structure. When the temperature is between 1 050-1 150 °C, the ring structure still has small holes, and when the temperature rises to 1 200 °C, there are almost no pores. With the increase of carbon-oxygen ratio, the pore size of the ring material gradually increases, and when the carbon-oxygen ratio increases from 0.75 to 1.75, the pore size of the ring material increases from 0.36 μm to 0.87 μm, and it is obvious that the ring structure is gradually loosened. The particle size has a significant impact on the material ring, the larger the particle size of the material, the more difficult it is to crunch, and the ring structure is relatively loose. When anthracite coal is selected as the reducing agent, the No. 1 fine powder circle mainly contains iron phase, silicate phase and iron spinel, and the No. 2 fine powder circle mainly contains iron phase and a small amount of iron oxide phase and some silicate phase. When PB powder is selected as reduced iron ore powder, bituminous coal rings mainly contain iron phase and silicate phase.

Sintered bodies were prepared using the hot pressing sintering process from Fe-Co-Cu pre-alloyed powders of varying particle sizes. The densification, Rockwell hardness, three-point bending strength, microstructure of the two sintered bodies of different particle sizes, and interface morphology between sintered body and diamond were comparatively analyzed. Furthermore, cutting experiments were conducted to assess the cutting speed, tool life, and diamond exposure of drill bits prepared using pre-alloyed powders with varying particle sizes to further investigate their performance disparities. The results indicate that the sintered body of DB-02, prepared with pre-alloyed powder of finer particle size, exhibits higher density (96.9%)and improved toughness (with a bending strength of 1 355.7 MPa).The modified tool design also results in enhanced retention force on the diamond, leading to improved cutting efficiency, extended tool lifes, and a maximum diamond exposure height of 154.2 μm during cutting experiments.

In response to the application requirements of tungsten-impregnated copper material in high-tempera‐ ture gas erosion, the tungsten- infiltrated copper material (W-7Cu) experienced high-temperature gas erosion was analyzed. The focus was on the morphological features of the similar nut-shaped that appeared on the surface of W-7Cu after burning.The microstructure was observed by SEM and metallographic analysis. The loss of copper was estimated through energy spectrum. The phase structure changes was analyzed by XRD. The results show that Cu loss occurres in everywhere of the materials, and C is presented on both the outer and inner surfaces. Both of the inner and outer surfaces contain a large amount of W6C2.54 and WC phases. Under high temperature and high-speed particle flow, the C particles enters the W skeleton formed after Cu precipitating and reacts with W to form new low-melting phases, which induces the ablation accelerating.

Cu/Al laminated composites are more and more widely used because of their high cost-effective synergistic effect. However, the interface structure, microstructure of copper layer and aluminum layer of Cu/Al composites prepared by different process methods are different, and the mechanical properties are different. The difference in interface bonding characteristics leads to macroscopic quality problems such as dislocation, delamination, and copper layer surface tearing during deep processing, which seriously restricts its application in high-end fields. In this paper, the research status of atomic scale of copper-aluminum laminated composites is introduced. The research progress of molecular dynamics simulation on the interface layer structure, diffusion and solidification, the correlation between heterogeneous interface characteristics and mechanical properties of copper-aluminum laminated composites is reviewed. The advantages and disadvantages of different potential functions in molecular dynamics simulation of copper-aluminum laminated composites are analyzed. It is proposed that accurate model, reasonable force field and accurate parameters are the three basic criteria for material atomic scale simulation, which provides a reference for the study of atomic scale of metal laminated composites.

Copper and its alloys are renowned for their excellent thermal and electrical conductivity, and various other beneficial properties. Integrating these materials with the design flexibility offered by 3D printing technology can significantly improve the efficiency of heat exchange and current transmission. A comprehensive overview of recent advancements in 3D-printed copper and copper alloys was presented. It also provides a detailed comparison of the advantages and disadvantages of different forming methods, along with an analysis of existing challenges. Numerous studies indicate that achieving controlled shape and performance in 3D-printed components necessitates the integrated control and optimization of materials, structures, processes, and overall performance. However, the application of 3D printing technology to produce copper and its alloys still faces several hurdles. The low absorption and high reflectivity of copper towards laser energy complicate achieving desired structures through the selective laser melting and laser melting deposition processes. Additionally, the surface quality of components produced via the electron beam selective melting method is often suboptimal for precision manufacturing. Moreover, the binder jetting technology necessitates post-forming heat treatment, which can result in shrinkage and deformation issues. The potential applications for 3D-printed copper and copper alloys were explored, highlighting their contributions to the ongoing evolution and innovation within the advanced manufacturing sector.

Laser powder bed fusion (LPBF) exhibits significant advantages in the manufacturing of high-entropy alloys (HEAs) with complex shapes and good strength-toughness properties. To further enhance the mechanical strength of HEAs, adding Nb element is an effective way which could enhance the solid solution strengthening and second phase strengthening effects. However, the structure features of second phase formed during LPBF is prone to brittle fracture, resulting in the significant decrease in the toughness properties of HEAs. Therefore, it is of great significance to study the effect of heat treatment post-processing on the microstructure and properties of HEAs fabricated by LPBF. The CoCrFeMnNiNb_0.15 HEAs were successfully prepared by LPBF first, and then the evolution of phase structure, mechanical properties and fracture morphology were studied after heat treatment. The results show that the heat treatment prompts the structure transformation of Nb-rich Laves phase from the continuous network to the fine and dispersively-distributed particles, and partial Nb element precipitates from the matrix structure of the FCC phase. Besides, the matrix grains also grow up along the (111) crystal orientation. With the increase of heat treatment temperature, the Laves phase and the matrix structure become coarsened gradually. Due to the weakened solid solution strengthening, grain boundary strengthening and second phase strengthening effects after heat treatment, the plastic deformation capability of the FCC phase is improved, thus resulting in the failure mode changed from brittle fracture to ductile fracture. When the heat treatment temperature is 980 ℃, the CoCrFeMnNiNb_0.15 HEAs can obtain the well-matched strength-toughness properties, which shows the product of strength and elongation of 13.2 GPa%, ultimate tensile strength of (892 ± 13.4) MPa, and elongation rate of 17.4%.

The influence of sample thickness, heating temperature, and carbon spray layer on the thermal diffusion coefficient of beryllium material was studied. The results indicate that the thermal diffusion coefficient on the side of the sample with a thickness ranging from 2 mm to 6 mm tends to be consistent. The standard deviation of multiple tests with a thickness of about 2 mm is the smallest, and the test results are more accurate. It is recommended to use this thickness as the sample thickness for measuring the thermal diffusion coefficient of beryllium materials. The beryllium coefficient gradually decreased with the heating temperature by 77.9% when the temperature increased from 25 ℃ to 900 ℃. Under different cases of carbon spray layer, the thermal diffusivity tested is significantly different, and the thermal diffusive coefficient measured on the test sample surface is coated with thin and uniform graphite.