Aiming at the problem of WC sinking in preparing Ni/WC composite coating, the coating was fabricated by plasma transfer arc welding technology under the applied external magnetic field. The distribution of Ni/WC coating plus WC particles under the applied magnetic field was investigated, and the microstructure and properties of the coating were characterized by vickers durometer, SEM, OM and EDS. The results showed that WC was deposited near the coating fusion line when no magnetic field was applied, while WC particles were concentrated in the middle area of the coating when the magnetic field was applied, with a distance of 420 μm from the bottom of the area to the coating fusion line. The hardness of the coating fluctuated with the applied magnetic field. The maximum value of the hardness was 1400HV without external magnetic field, and it was 1450HV with external magnetic field. In the experiment, WC particles almost did not melt and the particle morphology remained intact. The magnetic field refines the coating structure, promotes the generation of hard phase and improves the hardness of the coating. The external magnetic field solves the problem of WC subsidence and could be adjusted according to the engineering requirements.

The heat treatment process is important to improve the forming quality of laser cladding coatings. In this paper WC@Ni / Ni60A and rare earth mixed powder were used to investigate the influence of different heat treatment processes on the microhardness, microstructure, phase composition, and residual stress of the cladding layer and to explore the optimal annealing temperature. The results show that increasing heat treatment temperature decreases the coating microhardness. Higher microhardness of the coating can be obtained at 700 ℃. Samples with 1% La 2O3 and with 0.5% Y2O3 have a hardness of 64.9HRC and 65.3HRC, respectively. With the increase of heat treatment temperature, the wear volume becomes larger. At an annealing temperature of 700 ℃, the friction coeffi‐ cient of the sample is lower than that of the untreated one. The increase in heat treatment temperature helps to re‐ duce the residual stress. Considering the performance indexes, the optimal heat treatment scheme includes the fol‐ lowing parameters: the heating temperature is 700 ℃, the heating speed is 10 ℃/min, the insulation time is 60 min, and cooling mode is furnace cooling. The results provide a theoretical basis for improving coating quality through heat treatment.

The low oxygen MHC alloy plates were prepared by powder metallurgy and hot rolling method. The microstructure, and mechanical properties of low oxygen MHC alloy rolled plates were studied by chemical analysis, metallographic analysis, hardness test, and tensile mechanical property test. The results show that molybdenum powder reduction, and vacuum sintering, the oxygen content in the alloy can be effectively reduced by adjusting C/Hf atomic ratio. The comparison of microstructure analysis and mechanical property test results of samples annealed at different temperatures, the recovery stage of the alloy is below 1 300 ℃. With the increase of annealing temperature, recrystallization begins at 1 300 ℃, the strength and hardness gradually decrease, and the plasticity increases. The recrystallization is completed at 1 600 ℃. The low oxygen MHC alloy with complete recrystallization has excellent plasticity.

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.

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.

Metal powder injection molding technology is an advanced processing method of titanium alloy. The quality of injection molding products is closely related to the properties of feedstock, uniformity and rheological properties are important indexes to feedstock. In this paper, the effect of spherical powder size distribution on the properties of TC4 titanium alloy feedstock was studied by microscopic morphology analysis, uniformity and rheological properties analysis. The results show that the loading of feedstock can be effectively enhanced by increasing the distribution width of spherical powder size. Reducing distribution width of powder size is condu‐ cive to improving the uniformity of feedstock. Increasing the spherical particle size and reducing distribution width of powder size are two approaches to enhance the fluidity of feedstock.

Laser Powder Bed Fusion (LPBF) technology has significant advantages in rapid prototyping of complex structures and is widely used in many fields. However, the complex process characteristics of LPBF make its formed parts prone to pore defects such as porosity and lack of fusion. Laser powder bed melting experiments and numerical simulations were conducted on Inconel 718 alloy, which is widely used in aerospace, shipbuilding, and energy fields. This article combined experimental forming and numerical simulation methods to conduct research. The discrete element method was used to establish a random powder bed model, and the dynamic flow evolution process of the LPBF melt pool was simulated through computational fluid dynamics methods. This article analyzed the influence of key process parameters such as laser power, scanning spacing, and scanning speed on forming defects. Combining experimental detection and discrete element simulation, the mechanism of pore defects such as porosity and lack of fusion was discussed, and the optimal process parameter data was obtained through analysis.When the laser scanning spacing decreases, the porosity of the longitudinal section of the sample decreases; When the laser scanning speed increases, the number of non fusion defects at the edges of the sample increases; When the laser power increases, the number of pores inside the sample significantly decreases, and irregular non fusion defects appear at the edge of the melt. At a laser scanning interval of 80 μm. When th e laser scanning speed is 500 mm/s and the laser power is 200 W, a sample with appropriate melt width, fewer forming defects, and lower porosity can be obtained.

Titanium and its alloys are widely used in aerospace, automobile and ship, petrochemical industry, biological medicine and other fields because of their low density, high strength, good corrosion resistance and good biocompatibility. The article mainly aims at the preparation technology of powder metallurgy of titanium and titanium alloys, current situation are introduced. Powder manufacturing and densification at home and abroad are introduced. It is pointed out that the key for the future development of powder metallurgy titanium alloys is the preparation of low clearance element fine titanium powder, large size green and high performance sintered preform.

Magnesium alloys are the lightest metal structural materials, characterized by low density, high specific strength and stiffness, excellent damping，shock absorption properties, and good biodegradability. Traditional manufacturing methods of magnesium alloys, such as casting and extrusion, find it challenging to produce complex geometries in a single step. Cast magnesium alloys often suffer from coarse grains and poor mechanical properties due to low cooling rates, while extruded magnesium alloys are prone to defects like oxidation inclusions during forming. In contrast, additive manufacturing (AM) technology offers the advantage of rapid integrated forming and has gradually been applied to the production of magnesium alloys. Currently, the main AM technologies for magnesium alloys include Laser Powder Bed Fusion (LPBF), Wire Arc Additive Manufacturing (WAAM), Additive Friction Stir Deposition (AFSD), and Binder Jetting (BJ). The current status of additive manufacturing of magnesium alloys, analyzing of the forming principles, characteristics, and specific alloy properties of these four AM technologies were reviewed. The research status and existing problems of these four additive manufacturing techniques for magnesium alloys were discussed, their advantages and disadvantages were summarized, and aims to promote the research progress of magnesium alloy additive manufacturing technology.

The effect of deformation on the depth of the surface densification layer of powder metallurgical Fe-CuMn-Mo-C materials was investigated using plastic densification techniques. By increasing the amount of deforma‐ tion, the pores on the surface of the parts were reduced and the surface densification depth and hardness were im‐ proved. The experimental results show that the surface of the powder metallurgy parts prepared by extrusion densi‐ fication technique can form a uniform densification layer and the surface hardness of the parts can be improved. When the finished deformation is increased to 0.4 mm and 0.6 mm, a dense layer of about 0.25-0.4 mm is formed on the surface of the powder metallurgical parts with a specimen density of 6.8 and 7.0 g/cm3. The depth and hard‐ ness of the surface dense layer increase with the amount of deformation, indicating that the amount of deformation is one of the most important factors influencing the surface densification effect of the parts.

Mass production of high grade stainless steel powder for MIM (metal injection molding) was produced by combined atomization technology of water and gas. The design of nozzle, optimization of refractories, control of powder oxygen content and research on powder treatment technology were discussed in the present work. In comparison with the common stainless steel powder 316L and 17-4PH, the properties of produced powder have reached the advanced level of international similar products. Industrial scale production of 500 Kg is realized, and the production capacity of special alloy powder can reach 10 thousand tons per year.

Titanium alloy has the characteristics of high strength, lightweight, and high temperature resistance, making it a promising aerospace structural material. The traditional mechanical manufacturing process is difficult and costly, which limits the application of titanium alloys. Additive Manufacturing (AM), as an emerging advanced manufacturing technology, can produce metal components with high three-dimensional accuracy through layer by layer machining, providing near net shape machining for titanium alloys. This article first introduces the preparation technology of spherical titanium alloy powder, including Plasma Rotating Electrode Atomization Process (PREP), Electrode Induction Gas Atomization (EIGA), Plasma Atomization (PA), and Plasma Spheroidization (PS). The preparation technology and advantages and disadvantages of four spherical titanium alloy powders are compared, as well as their applications in aviation additive manufacturing, including Laser Selective Melting (SLM). The application characteristics and development trends of different titanium alloy powder preparation technologies in aviation additive manufacturing are summarized, such as Electron Beam Selective Melting (EBSM) and Laser Melting Deposition (LMD). It is pointed out that the key to the future development of spherical titanium alloy additive manufacturing is the preparation of low gap titanium powder. High precision, high efficiency and large scale of additive manufacturing equipment will be the future development trend.

Platinum rhodium alloy (PtRh20) powder was prepared in pure aqueous medium by spark plasma. The impurity content, surface morphology, composition and particle size distribution of the powder were analyzed by ICP, SEM and laser particle size analyzer. The results show that the efficiency of PtRh20 alloy powder prepared by electrospark plasma erosion method is up to 1 000 g/h, and the purity of the powder is high. It is composed of high spherical particles and floccules with the same composition. The particle size of the powder is basically between 5-60 μm, and the average particle size is 25 μm.

Metal injection molding (MIM) technology was adopted to prepare tungsten-copper alloy. Particle size and particle shape of the selected copper powders was quantitatively characterized by image analysis technology. The influence of the copper powders on the microstructure and properties of MIM tungsten-copper alloy was investigated in detail. By comparing，the characteristic parameters such as particle size, particle size distribution width, aspect ratio, roughness, outgrow and bluntness of the copper powders, the particle sizes of the crushed copper (CCu) powders and the water atomized copper (WCu) powders were much smaller than that of the reduced copper (RCu) powders, however the CCu powders exhibited wider particle size distribution and better regularity, surface smoothness and dispersion microstructure than the WCu powders and RCu powders. With tungsten powder blended with the CCu powders as raw materials, the tungsten-copper green parts were prepared by MIM showed high density and few defects. After sintering, the tungsten-copper alloy has the best microstructure and properties, with a density of 96.2%, a hardness of 235 HV, a bending strength of 1 200 MPa, a thermal conductivity of 128 W/(m·K) and an electrical conductivity of 30%IACS.

The development and application of hot extrusion process for P/M superalloys in Europe and US were summarized. The research progress of hot extrusion process for P/M superalloys in China was described. The selection principles of extrusion process parameters for René 95, René 88DT and FGH4096 alloys were introduced. The influence of extrusion process parameters (extrusion ratio, extrusion speed, extrusion temperature, etc.) on the extrusion forming, microstructure and properties of P/M superalloys was emphatically expounded. The evolution behavior of non-metallic inclusions in P/M superalloys during hot extrusion was clarified.

Cu-Sn powders were prepared by pre-mix and pre-alloy process, the microstructure and phase changes of Cu-Sn alloy were studied after sintering, and the sintering properties of Cu-Sn powders prepared by these two methods were tested and compared. The experimental results show that the microstructure of pre-mixing CuSn10 and CuSn20 is composed of α phase and α + δ eutectic tissue after sintering, while that of pre-alloy CuSn10 is α phase. After sintering, the pre-mixed Cu-Sn green compacts expand, on the contrary the pre-alloyed green com‐ pacts shrinkage. In addition, the strength, oil content and effective oil content of the pre-alloyed Cu-Sn parts are higher than those prepared by the pre-mixing method.

The experiment selected water atomization, gas atomization and centrifugal atomization to prepare 316L stainless steel powder, the magnetic conductivity of different kinds of powder grading was tested, the microstructure was characterized by SEM, EDS and XRD, and the effect of the preparation method on the magnetic conductivity of 316L stainless steel powder and the causes were investigated. The study shows that the 316L stainless steel powders prepared by atomization have magnetic conductivity, and the reason for magnetic conductivity is the existence of high temperature δ ferrite phase in the powder. The finer the particle size of the powder, the faster the cooling speed, the more cytocrystalline content, the higher the δ ferrite content, and the stronger the corresponding magnetic conductivity. The magnetic permeability of the powder prepared by water atomization is the highest, of the centrifugal atomization is centered, and of the powder prepared by gas atomization is slightly lower. The cooling capacity of centrifugal atomization is higher than gas atomization.

Aluminum alloys, which have the advantages of low density, high specific strength, and good corrosion resistance, are widely used in aviation, shipbuilding, automobiles, and other fields. Selective laser melting forming (SLM) is a promising technology that can fabricate complex parts at one time. In this study, the friction and wear properties of Al-Cu-Mg alloy fabricated by selective laser melting (SLM) were studied and compared with those of a cast ZL205A alloy with a similar composition. The results show that the SLM process can refine the alloy grains, change the size and distribution of Al2Cu, and make the grains smaller and more uniform. Compared with the cast ZL205A alloy, the wear rate and friction coefficient of the SLM-fabricated Al-Cu-Mg alloy decreased in varying degrees. SLM-fabricated Al-Cu-Mg alloy has the best wear resistance in cross section, followed by longitudinal section, and cast ZL205A has the worst wear resistance. The wear mechanisms of SLM-fabricated Al-Cu-Mg alloy are different under varying loads: the wear mechanisms at low load are mainly abrasive, and a little adhesive and plastic extrusion wear; the wear mechanisms under medium load are abrasive, adhesive and oxidation wear; the wear mechanisms under high load are mainly a combination of delamination, adhesive and oxidation wear.

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.

The tape casting method is applied to the production of metal films. Due to the large specific gravity of the metal powder and the complicated preparation process of the casting process, the metal film is easily deformed and cracked. In this paper, the influence of the content of various additives in the metal casting slurry on the form‐ ing process and sintering properties of the metal film was studied. The result shows that the binder content and vis‐ cosity have a decisive influence on the performance of the metal film. Adding 10% pore-forming agent can effec‐ tively control the phenomenon of particle agglomeration, membrane pore size distribution is concentrated, the gas transmission rate increases. The influence of solid content on the uniformity of the slab is verified. The solid con‐ tent is too low can cause surface cracking, uneven thickness, many defects and poor strength after sintering. And the solid content is too high, will lead to the film layer gas permeability decline, at the same time, the flexibility of the film layer will also be reduced. Pore forming material can significantly improve the surface agglomeration phe‐ nomenon of membrane layer and improve the binding force between particles.

CoCrFeNi high entropy alloy has become one of the most popular systems in the pursuit of high toughness parts research because of its excellent plastic deformation ability and high yield strength of a single stable facecentric cubic solid-solute structure. At the same time, selective laser melting technology has unparalleled advantages over traditional preparation methods due to its flexible forming size and ultra-fast heating and cooling rates. In this paper, the CoCrFeNi-X high-entropy alloy systems successfully created by the selective laser melting technology in recent years and the effects of tissue structure on mechanical properties for eight different alloy systems in terms of phase structure and tissue morphology were analyzed；the effects of the preparation process on forming density and mechanical properties for three CoCrFeNi-X high entropy alloys formed parts were examined；Finally, a detailed analysis of the current status of the two mainstream alloy systems, CoCrFeNi-Alx and CoCrFeNi-Mn, was done on the alloy composition design. The research and analysis are expected to provide some theoretical guidance for the experimental research and industrial application of preparing CoCrFeNi-X system high entropy alloys by selective laser melting technology.

TA15 titanium alloy samples were prepared by selective laser melting (SLM) forming technology. The effects of heat treatment on microstructure, tensile and impact properties of TA15 titanium alloy samples were stud‐ ied. The results show that under the single heat treatment mode, with the prolongation of holding time and the in‐ crease of annealing temperature, α' martensite in the microstructure gradually decomposes, and the volume fraction of the secondary α phase and β phase gradually increases, and the tensile strength of the samples show a downward trend, but the fracture toughness increases at first and decreases subsequently. Under the heat treatment system of 850 ℃ for 4 h, the sample has better comprehensive properties, its tensile strength is 1 033 MPa, and the impact en‐ ergy is 38 J. Under the double heat treatment mode, the microstructure is mainly a basket-weave structure α+β twophase structure, the degree of microstructure homogenization is higher, which shows that the dispersion of macro‐ scopic properties is smaller, with an average tensile strength of 1 029 MPa and impact energy of 40 J.

In recent years, the demand for high-strength-high-plasticity metal materials in the fields of automobiles and ships has been increasing. In order to obtain high-strength-high-plasticity metal materials, powder metallurgy technology plays an increasingly important role. In this study, the mixed metal powders of martensitic steel and austenitic steel with a mass ratio of 2:1 were sintered by spark plasma sintering (SPS), and the austenite phase was uniformly distributed in the martensite phase. The density of the sample is as high as 95.5%, and through the subsequent hot rolling treatment, the sintering quality of the composite steel is improved, and the density is increased to 98.9%.The yield strength, tensile strength, uniform elongation and total elongation of the clad steel after hot rolling are 960 MPa, 1 529 MPa, 6.7% and 6.7%, respectively. On the basis of hot rolling, cold rolling + short-time high temperature tempering treatment is introduced, and the performance of powder metallurgy composite steel is further improved. Among them, the clad steel cold-rolled at 30%-500℃ and tempered for 5 min has yield strength, tensile strength, uniform elongation and total elongation of 1 899 MPa, 1 964 MPa, 9.2% and 10.0%, respectively.

In this paper, the mechanical properties, microstructures and fracture surfaces of TC4 powder titanium alloy prepared by hot isostatic pressing were compared and analyzed, and the effect of oxygen content on its mechanical properties was studied. The results show that the microstructures of TC4 titanium alloys as hot isostatic pressing and annealing have no obvious difference and are lamellar; the oxygen content increases from 0.11% to 0.17%, the strength and plasticity of titanium alloys increase obviously, and the fracture toughness KIC of TC4 titanium alloys decreases from 101 MPa·m^1/2 to 95 101 MPa·m^1/2; the fracture mechanism of TC4 titanium alloys under room temperature tension is typical microporous aggregation fracture. The mechanism is that cleavage facets appear on the tough section with the increase of oxygen content.

In order to extend the service life of heating surface tubes of a boiler by increasing its wear resistance， the technology of high velocity arc spraying are utilized to prepare wear-resistant coating of Ni55 on the surface of SA-210C. The spray coating was remelted by a tungsten electrode argon arc welding machine and the microscopic structure，phase composition，bonding strength，microhardness and erosion resistance of the substrate and coating was investigated. The results show that the coating crystal is mainly composed of γ-（Fe，Ni）、Ni3Fe、CrB、 Cr7C3、Cr23C6、Fe3B and WC. The coating forms a typical lamellar structure during deposition，which is mainly dominated by mechanical bond and has good compactness. The bonding strength of spray coating is 40.85 Mpa which is prompted to 53.25 MPa after remelting. The average hardness of the spray coating is 1 081HV which was also prompted to 1 143HV after remelting. In the conditions of erosion angle of 45°，erosion velocity of 200 m/s and temperature of 600 ℃，the remelting coating has the best erosion wear resistance，and the spray coating has better erosion wear resistance than substrate metal. The erosion wear behavior of the remelting coating is same as brittle materials. The hard phases like CrB、Cr7C3、Fe3B are combined strongly with coating，which has the function of resisting continuous cutting by abrasive grains. The erosion mechanism is the peeling of the oxide film and the micro-cutting and ploughing of the substrate metal by the abrasive particles.

HSS and tool steels perform specially with their high mechanical and thermal properties such as high strength and toughness, high hardness, high wear resistance, and good heat resistance, which are widely used in in‐ dustries such as metalworking, plastic injection molding, and automotive manufacturing, etc. Conventionally, they are prepared by traditional casting and forging process, which always introduce compositional segregation and coarse carbides in their microstructure. These micro defects are difficult to eliminate through conventional process‐ ing methods such as forging, leading to the deterioration in material properties. The powder metallurgy process pro‐ vides an uniform microstructure, fine dispersive carbides, and high alloy composition, which allows for the manu‐ facturing of complex shapes and structures of the final products. Through this approach, the tool and die products have the advantages of higher performance, higher precision, and longer life, and have important applications pros‐ pects in the high-end manufacturing industry. In this work, a comprehensive review of the production technologies and applications of powder metallurgy HSS and tool steels are provided. Besides, the technological innovations in the industrial production, the manufacture methods, and the microstructural properties of powder metallurgy HSS and tool steels are discussed in details. Furthermore, the classifications and applications of these materials, offering an outlook on the future development trends in powder metallurgy HSS and tool steels are summarized.

The selective laser melting forming technology is increasingly used in the manufacture of complex com‐ ponents for aerospace equipment. However, such parts have thin-walled curved features have a large residual stress, which could induce large residual stress and deformation and seriously restrict the forming accuracy and quality. AlSi10Mg is widely used in the production of parts in the field of additive manufacturing due to its low density, high specific strength and good corrosion resistance. In this paper, we analyze the influence of the process parameters and geometric features on the support connection by simulating the laser-selective melting of thinwalled surface features under non-solid support, and study the residual stress distribution and deformation law of the surface features under non-solid support based on this simulation. The thermoplastic method is used to simulate the connection of the non-solid support with different support forming laser power and support structure, and the support parameters are selected with the goal of connection effect. The residual stress and deformation distribution of thin-walled surface features with different wall thicknesses and forming heights are simulated, experimentally verified and discussed based on the intrinsic strain model with the application of the selected support parameters. The simulation results show that the strength of the non-solid support connection is related to the laser power. The decrease of the laser power leads to the decrease of the stress level at the support connection. The stress values at the support connection of each group decrease by14.7%,14.6% and 17.3% respectively with the decrease of the la‐ ser power. When optimizing non-solid support parameters for forming simulation and experiment of thin-walled curved parts, it is found that the peak deformation of thin-walled curved parts increase with the rise of forming height, and the thinner the wall thickness of the parts, the greater the peak deformation. Under the condition of using laser power of 350 W, 3×3 grids and adding independent external contour support, the non-solid support con‐ nection effect of AlSi10Mg is the best, and with the increase of laser power, the support connection is also stronger. The addition of non-entity contour support can effectively improve the support connection. The local deformation of thin-walled curved parts with non-solid support is obviously improved. The residual stress distribution of thinwalled curved parts is mainly affected by the Z-direction normal stress of the parts, and increases with the increase of the thickness of the parts.

Aluminum powder is the most commonly used metal fuel in the explosives and propellants industry. How to make aluminum powder react as completely as possible in explosives and propellants has always been a difficult problem to solve. The combustion-assisted materials and technologies for aluminum powder are systematically reviewed and the different mechanism of promoting the combustion of aluminum powder is analyzed in this paper. Ammonium perchlorate(AP), fluorine-containing materials, nitro-containing compounds, azide-based materials, etc. have significant auxiliary effects on the oxidation of aluminum powder, and the aluminum-containing composites prepared by self-assembly process can help aluminum powder react completely more effectively.

Cemented carbides, composed of refractory metal carbide (WC, TiC, NbC, etc.) and metallic binder phases (such as Fe, Ni and Co), are prepared by powder mixing, pressing, and then sintering. However, the traditional powder metallurgy method is expensive to fabricate molds, and it is difficult to make complex parts. In contrast, additive manufacturing (AM, also named as "3D printing") adopts digital lamination processing technology that enables to achieve fast and precise forming. One of the most critical steps for achieving high-quality products is researching and developing cemented carbide powders suitable for additive manufacturing. At present, the preparation methods of cemented carbide powders for additive manufacturing are mainly divided into the following four categories: mechanical alloying, spherical WC surface coating technology, spray drying technology and plasma spheroidization technology. These four methods differ in fabrication principle, cost, and flexibility of forming method. Four common preparation methods mentioned above of cemented carbide powders fabricated by AM were reviewed, the physical characteristics and forming properties of the prepared powders were compared, and the principles of powder preparation, their respective advantages and disadvantages, and the suitable additive manufacturing process were analyzed, in order to promote the research and development of cemented carbide powders made by AM.

In this paper，93W-5Ni-2Fe tungsten heavy alloy prepared by powder metallurgy method were tested at 1 000，1 100，1 200，1 300 and 1 400 ℃，the high temperature mechanical properties were investigated respectively. The fracture analysis and the developing principles of fracture mechanism were studied. The results show when the elevating temperature is 1 000- 1 400 ℃ ，mechanical properties of 93W- 5Ni- 2Fe alloy，such as tensile strength，elongation，reduction of area and Young's module get worsedramatically. Material becomes brittle，transgranular fracturecan be hardly found，binder phase tear and inter-facial fracture between tungsten grain and binder phases are domestic fracture mode.

Cu-based friction materials with different lubrication component such as the flake graphite, spherical graphite, coke, artificial graphite, and cryptocrystalline graphite, were prepared by powder metallurgy technology. The tribological and brake performance of Cu-based friction materials with different lubrication component were tested by the MM3000 friction and wear tester. The results show that the average friction coefficient of the Cubased friction material with artificial graphite as lubrication component is the highest (> 0.40), but the wear loss is the largest of all at the speed of 3 000~7 000 r/min. The friction coefficient of the Cu-based friction material with coke is the second (> 0.375), and the wear loss is the smallest of all. The friction coefficient and wear loss of the Cu-based friction material with coke is good than the Cu-based friction material with commonly used flake graph‐ ite. Under the braking condition of 7 000 r/min, the instantaneous friction coefficient of Cu-based friction material with artificial graphite is the highest, and the braking time is short. However, the surface temperature rise of the Cu-based friction material with artificial graphite is the largest. The instantaneous friction coefficient and braking time of the Cu-based friction material with coke is second, but the surface temperature rise of friction material is the smallest. The overall performance of the Cu-based friction material with coke is better than the friction material with flake graphite. Therefore, Cu-based friction materials with coke as lubrication component have better tribolog‐ ical and braking properties, relatively.

Based on the test and analysis of static mechanical properties of TA15 titanium alloy samples formed by selective laser melting, the fatigue properties of TA15 titanium alloy samples formed by selective laser melting at room temperature were studied and analyzed. Tensile properties, impact properties and fatigue properties of TA15 titanium alloy samples at room temperature were tested by universal testing machine, impact testing machine and fatigue testing machine. Optical microscopy (OM) and scanning electron microscopy (SEM) were used to analyze the microstructures of the cross-sectional and longitudinal sections, as well as the tensile and fatigue fractures of the samples. The research shows that the cross section presents a typical checkerboard lattice structure, and the longitudinal section distributes β columnar crystals penetrate through multiple deposition layers and grow epitaxially, and acicular martensite is staggered inside the columnar grains. The tensile strength of the transverse and longitudinal samples after annealing treatment, the strength and yield strength are lower than that of the as-deposited samples, and the elongation, shrinkage and impact strength are significantly improved, and they are all better than the TA15 bar index. The fatigue life data has a certain dispersion, which is the main reason for the fatigue dispersion. It is a selective laser melting and forming process. The metal powder is rapidly melted and cooled under the action of a high-energy laser, and defects such as poor overlap, pores, and unmelted powder appear randomly inside the part. The depositional cross section of TA15 titanium alloy formed by selective laser melting presents a typical checkerboard lattice structure. The longitudinal section is distributed with β columnar crystals growing epitaxial through several sedimentary layers. The columnar crystals are interleaved with acicular martensite. The ratio of length to width of primary and secondary α phases in annealed microstructure decreases continuously, and the spicules are coarsened continuously to form strip. After being held at 850 ℃ for 2 h, the tensile strength and yield strength of the transverse and longitudinal samples of TA15 titanium alloy decrease, while the elongation, shrinkage and impact strength of the samples are significantly increased, which are better than those of TA15 sheet. Fatigue life data of annealed TA15 titanium alloy in selective laser melting forming (stress ratio R=0.06, Kt=2.5) have a certain dispersion. The main reason for the fatigue dispersion is the rapid melting and cooling of metal powder under the action of high energy laser. Defects such as poor lap joint, air hole and unmelted powder appear randomly in the parts.

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.

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.

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.

3D printing is a new type of manufacturing technology, which is widely applied in the field of aero‐ space, medical treatment, automobile, ships.Titanium alloy is an important part of metal 3D printing system due to its excellent properties such as light weight, high specific strength, good corrosion resistance and excellent biocom‐ patibility. The performance requirements of titanium materials and main preparation methods of powder of 3D printing were briefly described. The characteristic of GA and PREP preparation technique were compared, and the reason for the difference of GA and PREP preparation technique were explained emphatically. At last, research directions and application prospects were expounded.

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%.

A TiC high manganese steel-bonded carbide with 0.1% boron addition was fabricated by powder metallurgy techiniques using TiC as hard phase and Fe, Ni, Mo, Mn, graphite C raw powders as the binder, and effects of sintering temperature on the microstructure and properties of the alloys were carried out. Microstructure observation shows that the structure of the alloy consists of black core-gray rim ceramic particles and white metallic binder, while, the ceramic particles grow gradually and its distribution become evenly with the temperature increase. The relative density of the alloy increases firstly and then decreases with the temperature increase, subsequently, the relative density of the alloy increases monotonously with the temperature increase and reaches the maximum value 98.29%. Mechanical properties results show that the hardness, transverse rupture strength (TRS) (in the as-sintered state and heat treatment state) and impact energy (IE) of the alloy increased monotonously with the temperature increase, also, reach the maximum value 63.8HRC, 1 993 MPa/1 425 MPa and 9.3 J/cm². The alloy densifies singnificantly when sintered from 1 320 ℃to 1 340 ℃, then, the hardness, TRS and IE of the alloy increases obviously. Subsequently, the increase rate of the hardness, TRS and IE of the alloy slow down which indicates the distinct role of B element in promoting densification. Boron element begins to volatilize and is exhausted completely at 1 420 ℃.The experimental alloy with B addition and the high manganese steel matrix are cast into a whole part, no obvious defects as cracks, impurities and pores are observed between the interfaces showing excellent interface bonding state and prospective long service life.

Lithium is the lightest metal element. If 1% lithium is fused into aluminum alloy, the alloy density can be decreased by 3% and the elastic modulus can be increased by 6%. Due to its excellent strength, corrosion resistance, fatigue resistance and ductility, aluminum-lithium alloy has become an ideal lightweight high-strength material in the aerospace field. The traditional melting casting method has certain limitations when fabricating aluminum lithium alloy, such as the need for special melting casting equipment, easy to produce porosity, cracks and other defects. The need for forging, extrusion and other processes after casting increases the manufacturing cost and prolongs the manufacturing cycle. However, additive manufacturing technology can avoid these problems and provide a new solution for the processing and manufacturing of aluminum lithium alloy. In this paper, the microstructure and properties of additive manufacturing aluminum-lithium alloy are summarized, the main technology research situation of additive manufacturing aluminum-lithium alloy is concluded, and the development trend and prospect of additive manufacturing technology in the preparation of aluminum-lithium alloy in the future are analyzed.

PCBN (polycrystalline cubic boron nitride) superhard tool materials were synthesised under high tem‐ perature and high pressure conditions using CBN/Ti/Al as raw materials. The effects of the synthesis pressure on the flexural strength, wear resistance and interfacial morphology of the PCBN composites were investigated. The results show that the flexural strength and wear resistance of the PCBN composites increases as the synthesis pres‐ sure is increased. The bonding interface between the cemented carbide matrix and CBN is analysed by scanning electron microscopy. The test results show that increasing the synthesis pressure can improve the interfacial bond strength of the PCBN material, reduce the occurrence of delamination and cracks, and improve the yield of the syn‐ thesised product. Also, within the pressure range at 5.5-7 GPa, PCBN has better flatness, less CBN thickness differ‐ ence and higher product utilisation in cutting. The performance of the synthesised tool material at 7 GPa is relative‐ ly close to that of Sumitomo BN700 in machining gear parts, with good market prospects.