Aluminum nitride ( AlN ) has become a key material in the field of electronic packaging and thermal management due to its excellent thermal conductivity, insulation and thermal expansion coefficient matching with silicon. However, AlN powder is easily hydrolyzed with water or in a humid environment to form aluminum hydroxide (Al(OH)3) or hydroxyl alumina ( AlOOH ), resulting in the loss of nitrogen content and the increase of oxygen content, which reduces the thermal conductivity of subsequent ceramics and thermal interface material, hindering the industrial application. In this paper, the hydrolysis mechanism of AlN powder is systematically reviewed, and the regulation of various factors on the hydrolysis behavior is clarified. The surface modification technology of aluminum nitride powder is reviewed. Finally, the problems existing in the current research are pointed out, and the future development direction is prospected, which provides theoretical support and technical reference for the efficient application of AlN powder in the field of electronic devices.
As an economic technology with the advantages of powder metallurgy and precision hot die forging, powder forging is a near-net-shape manufacturing technology, which produces parts with high precision and excellent mechanical properties by forging the preformed sintered compact. In this study, we provide a strategy to study the powder forging process as well as the mechanical properties of aluminum alloys using 6061 as an example. The constitutive equations and thermal processing maps of the sintered 6061 aluminum alloy are established through the thermal simulation, and on the basis of thermal analyses, the 6061 aluminum alloy is fabricated via powder metallurgy followed by precision hot die forging. Investigation on the microstructure and mechanical properties of as-sintered and as-forged aluminum alloys before and after T6 heat treatment are also carried out. The results show that the sintered 6061 aluminum alloy without instability during deformation in the range of 425-500 ℃/0.01-1 s-1, indicating its excellent hot workability. Compared with the as-sintered alloys, the average grain size of as-forged alloys decreased from 12.3 μm to 9.6 μm, which enabled a uniform distribution of alloying elements. As a result, the density, hardness, yield strength and tensile strength reach 99.71%, HV64.7, 129 MPa and 220 MPa, respectively. In particular, it is noted that the as-forged alloy experienced a 138% increase in its elongation, achieving 29.6%. After T6 heat treatment, the as-forged alloys exhibit a hardness of HV135.2, a yield strength of 301 MPa, a tensile strength of 308 MPa and an elongation of 12%, and the dominant strengthening phases are composed of β" and β phases.
The powder of GH4698 superalloy was prepared by supreme speed plasma rotating electrode processing (SS-PREP), and a test billet was sintered by hot isostatic pressing (HIP). After the standard heat treatment, the microstructure and tensile properties of the powder metallurgy GH4698 was investigation. In this work, the mechanical properties of GH4698 superalloy prepared by SS-PREP+HIP+heat treatment route can meet the requirements of forgings. The average tensile strength at room temperature and 750 °C is 1 325 MPa and 873 MPa, respectively, which is better than cast wrought+heat treatment process. The average elongation at room temperature and 750 ℃ are 26.7% and 6.6%, respectively, which is slightly lower than that of cast wrought + heat treatment process. The average impact energy and toughness at room temperature are 60.1 J and 75.3 J/cm2, respectively.
Through the combination of numerical simulation and experiment, the interaction mechanism between gas and liquid in the atomization process of Ni60A superalloy was studied, and the volume of fluid (VOF) multiphase flow model and DPM (discrete phase model) method were adopted. The influence of atomization pressure on the crushing process and particle size distribution of KHRT (kelvin-helmholtz rayleigh-transport) model during primary and secondary atomization of high-temperature melt was studied, and the results were compared with the experimental results. The results show that with the increase of atomization pressure, the return area increases gradually, and the particle size decreases first and then increases. When the atomization pressure is 2 MPa, the error between the particle size prepared by the experiment and the numerical simulation results is 4.8%, which verifies the accuracy of the numerical simulation of Ni60A alloy powder atomization crushing process.
To study on the influence of powder preparation processe on NiCrAlY powders and coatings.Atmospheric Plasma Spraying (APS) were prepared using Ni-Cr-Al-Y alloy powders fabricated by the close-coupled gas atomization and the ultrasonic gas atomization. The physical properties,morphology, elemental distribution,internal microstructure and phase composition of the NiCrAlY alloy powders and coatings were compared. The results show that the two powders have the similar chemical composition and physical properties,with both exhibiting a near-spherical particles shape,but differing in particle size composition.Their microstructures are both composed of dendrites and cell-like structure. The yield and the solidification cooling rate of close-coupled atomization powder with the particle size of 45-90 μm are 30.69% and 1.25-2.49×104 k/s. In contrast, the yields and the solidification cooling rate of ultrasonic gas atomization powder with the particle size of 45-90 μm are exceed 60% and 1.18-2.08×104 k/s, and the distribution of the dendrities and cellar crystals is more regular.Two APS coating have a typical layered structure. The coating fabricated by the close-coupled gas atomization powder has a porosity rate of 12.81% and a bonding strength of 36.8 MPa. In comparison, the coating fabricated by the ultrasonic gas atomization powder has a porosity rate of 11.35% and a bonding strength of 34.8 MPa. Close-coupled gas atomized and ultrasonic gas atomized powders differ in particle size distribution and phase structure. The coatings prepared from the two atomized powders have similar cross-sectional morphology, element distribution, and coating properties. For the close-coupled gas atomized powder contains more fine particles and has a complex phase structure, which leads to significant changes in the element content of the coating, along with poor crystallinity, high porosity, and high microhardness.
High-nitrogen steel samples were prepared by adding chromium nitride into the powder and using laser selective zone melting technology at atmospheric pressure, and the effects of different laser parameters on the organization, physical phase and mechanical properties of high-nitrogen steel were systematically investigated. The experimental results show that when the laser energy density increases, the defects of the samples show a trend of increasing and then decreasing. When the laser energy density is too high, it will aggravate the overflow of nitrogen in the powder to form more defects. The physical phase of the sample is dominated by austenite and ferrite, martensite and the austenite phase content of the sample decreases with the increase of laser energy density. The samples with chromium nitride added have a yield strength of 822-1 057 MPa at 1 134-1 254 MPa and an elongation of 9.6%-16.64%. The fracture behavior of the samples is mainly dominated by ductile fracture, and some regions are brittle fracture. The fracture behavior of the samples was mainly characterized by ductile fracture when the energy density was 130.21 J/mm3 (laser power 250W, scanning speed 800 mm/s, scanning spacing 0.08 mm, powder thickness 0.03mm), the overmatching powder laser selective zone melting and forming specimens showed the best mechanical properties.
Cu-12.5Ni-5Sn alloy was prepared using spark plasma sintering (SPS). The effects of sintering temperature, sintering pressure and holding time on the densification and mechanical properties of the alloy were investigated. The optimal SPS conditions as well as the relationship between microstructure and mechanical properties of the alloy were explored. The results show that the densification, hardness and yield strength of alloy all show a trend of first increasing and then decreasing with the increase of sintering temperature, sintering pressure and holding time. When the sintering temperature is about at 870 ℃, the sintering pressure is about 25 MPa, and the holding time is about 30 min, the densification of the alloy is above 98%, and the hardness and yield strength of the alloy after aging treatment reach the maximum values of 252HB and 468 MPa, respectively. Aging treatment can promote further refinement and formation of the lamellar structures in alloy. The γ-CuNi2Sn phases enriched with Ni and Sn with different shapes are formed at grain boundaries and within grains after aging treatment. In addition, the lamellar γ-CuNi2Sn phases are identified as discontinuous precipitated γ-DO3 phases, which are alternately arranged with the spinodal structures to form sandwich structures. The spinodal decomposition strengthening and precipitation strengthening are the main reasons for the good mechanical properties of the alloy.
As one of the important technologies in powder metallurgy, hot-isostati-pressing near-net-shape (HIP-NNS) technology has been widely used in the aerospace field in recent years, it has ability to prepare high-performance products with complex structures. Due to their excellent mechanical properties and corrosion resistance, duplex stainless steel (DSS) products have attracted attention from marine engineering, shipbuilding, nuclear power, petrochemical and other industries. HIP-NNS technology, Shima plastic deformation model and MSC. Marc finite element software were used in the paper. The densification of DSS powder simulation and the prediction of deformation size were completed, and the changes in powder relative density and equivalent stress were analyzed .The results show that the numerical model achieves high prediction accuracy, with a maximum size error of no more than 3%. The numerical simulation method is used to accurately predict the deformation of the package and the powder densification process, greatly improving powder utilization and production efficiency, reducing processing costs, and providing a innovative approach for achieving integrated forming of complex DSS products.
The nine-claw synchronizer cone ring is a critical component used in the lock-pin synchronizers of heavy-duty truck transmissions with high torque requirements. This study investigates the manufacturing process of the nine-claw synchronizer cone ring using powder metallurgy (PM) technology as an alternative to traditional casting and forged steel methods. The selected material is a diffusion-alloyed powder blend of Fe-0.5Mo-4.0Ni-1.5Cu-0.8C, and the manufacturing process includes powder compaction, sintering with copper infiltration, precision machining, and heat treatment. The resulting PM nine-claw cone ring achieves a density of 7.49 g/cm³, a surface hardness of HRC 31, and a tensile strength of 623 MPa, meeting all performance requirements for transmission assembly and service life in heavy-duty trucks. The powder metallurgy process overcomes the drawbacks of the original 40Cr cast steel cone ring, including excessive weight, high machining demands, complex procedures, low production efficiency, and high costs. This method offers advantages such as reduced machining, energy and material savings, high efficiency, and low cost, making it suitable for mass production.
A technology to modify the surface of the substrate with alumina powder particles was proposed, and the alumina particles with a diameter of tens of microns were successfully embedded into the metal surface layer of 5052 aluminum alloy at high speed and accurately by using a laser oscillator combined with a sandblasting device. The laser-induced powder jet technology uses a laser to melt the surface layer of the substrate only , and then uses high-speed jetting of alumina particles to quickly embed in the molten layer of the aluminum alloy substrate to enhance the surface properties of the material. The cross-section of the sample was observed by scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDX), and the depth of the embedded particles could reach about 100 μm, and the number and distribution range of the embedded alumina particles were detected. The effects of key process parameters such as jet pressure, laser energy flow density (the flow rate of laser energy per unit area) and particle incidence angle on the embedding depth, embedding amount and particle percentage were further discussed, which provided a theoretical basis and experimental data support for optimizing the process conditions of this technology. The successful development of this technology not only expands a new way of surface modification of materials, but also provides a new technical solution for improving the wear resistance and corrosion resistance of metal materials.
Preparing microstructures on the surface of metal materials and adding solid lubricants can improve their self-lubricating performance. In this paper, TiAl (TA) alloy with an equal-difference dendritic pore structure is prepared by powder metallurgy process, and the self-lubrication mechanism of SnAgCu-Graphene (SG) Composite solid lubricant on TA matrix is studied. Through experiments and theoretical analysis, the results show that when the SG Composite solid lubricant with the mass fraction ratio of SnAgCu and Graphene of 65 wt.% and 35 wt.% is added, the wear rate and average friction coefficient of the sample TASG/A first decrease and then increase with the increase of the number of microstructure branches. Among them, the wear rate of the sample TASG/A-4 is 1.38×10-4 mm3 N-1 m-1, and the average friction coefficient is 0.12, with the optimal lubrication effect. The experiments indicate that the dendritic pore structure can release enough SG Composite solid lubricant under the action of friction and mix with abrasive debris to fill the pits and cracks caused by friction.
In order to provide systematic theoretical support for the optimisation of the preparation process of metal-bonded diamond tools, the effects of different metals on the properties of diamond under hot pressing conditions were experimentally investigated. The metal bond prepared in the hot pressing and sintering process was corroded by the acid corrosion method, and the diamond obtained after corrosion was compared and analysed with the original diamond in terms of surface morphology, surface corrosion rate, corrosion depth, etc., and the diamond was tested for compressive strength. The results show that with the increase of temperature, the surface corrosion rate of diamond rises and the surface corrosion depth gradually increases, which leads to a significant decrease in the compressive strength of diamond. Under the same hot pressing conditions, after the hot pressing sintering of Fe, Co, Ni, Cu, Cr and Ti, the surface morphology and properties of diamond show different degrees of changes. Specifically, under the hot pressing and sintering condition at 700 ℃, Ti has the least effect on the compressive strength of diamond, and the corrosion rate and depth of diamond are 66.7% and 0.453 μm, respectively, compared with Cr and Fe, which have a significant decrease in the compressive strength of diamond, and the corrosion depth of diamond is higher than the corrosion results of the other metals. Raman analyses reveal that the surface structure and properties of diamond do not change significantly in most cases, and only a few graphite structures appear after Fe and Co corrosion.
Due to the brittleness, high hardness, and stable chemical properties of single crystal sapphire, there are challenges in the cutting process such as low processing efficiency, short lifespan, internal cracks, and surface scratches in the extracted crystal rod. Therefore, it is crucial to urgently address the need for an efficient and high-quality cutting process for sapphire. On diamond drill head formulation, a constrained formulation design method was adopted. The impact of different components on bit sharpness and lifespan was discussed. To evaluate these improvements, regression analysis was conducted by using SPSS to explore the relationship between the components. The identification of primary and secondary relationships between performance indices and each component along with statistical significance assessment was conducted through t-test analysis. Finally, an optimal matrix ratio scheme was obtained by using Excel solution. Experimental results demonstrate that the constructed Scheffe regression equation accurately predicts experimental outcomes. F-tests and t-tests on formula design test data reveal that WCu powder content has a significant influence on sapphire drill sharpness, with optimum sharpness achieved at 35wt% WCu powder while FCS20 is at 30wt% and Co powder is at 35wt%. This also leads to improved surface quality of the sapphire crystal rod. The constrained uniform formulation design significantly reduces testing efforts while obtaining optimal results.
The characteristics of single-pass and single-layer cold-sprayed pure Cu coatings have not been extensively studied. In this research, cold spray technology was employed to deposit single-pass and single-layer pure Cu coatings onto 6061 T6 Al alloy plates under varying gas temperatures and pressures. The surface roughness of the coatings was measured using a three-dimensional profilometer, while the thickness, microstructure, and phase composition were analyzed using OM, SEM, and XRD techniques, respectively. SEM images, in conjunction with Image Pro software, were used to calculate the porosity of the coatings. Additionally, the microhardness and shear strength of the coatings were evaluated using a micro Vickers hardness tester and a universal mechanical testing machine, respectively. The shear fracture morphology of the coatings was observed using SEM. The results indicate that an increase in gas temperature results in higher coating thickness and shear strength, accompanied by a gradual decrease in surface roughness, porosity, and microhardness. Conversely, increasing gas pressure lead to corresponding increases in surface roughness, microhardness, and shear strength, while reducing porosity. Ultimately, the study elucidates the relationship between the microstructure and mechanical properties of single-pass and single-layer pure Cu coatings and spraying parameters, laying a foundation for further research on high-performance pure Cu coatings.
Powder metallurgy Ti-22Al-25Nb（at.%）alloy uniform fine crystal slab was prepared by hot isostatic pressing process. The slab was rolled into 2 mm thick sheet by two rolling processes. The effects of two rolling processes on the microstructure and mechanical properties of Ti-22Al-25Nb alloy sheet were studied. The results show that the sheet prepared by the two rolling processes have high superplasticity （elongation 600%）at 940 ℃/1×10-3 s-1. The transverse and longitudinal tensile properties of the plates prepared by the two rolling processes are similar at room temperature, the tensile strength is about 1 100 MPa, and the elongation is greater than 6%. Rolling process B adopts high temperature annealing treatment and optimizes the ratio of transverse and longitudinal deformation during slab rolling. The transverse and longitudinal tensile strength of the prepared plates at 650 ℃ is greater than 800 MPa, the elongation is greater than 12%, and the transverse and longitudinal strength difference is low （the transverse and longitudinal strength difference is less than 6% at room temperature and 650 ℃）.
AlCoCrFeNi high-entropy alloy (HEA) particles were selected as the reinforcing phase to prepare HEA/Al composite materials using Friction Stir Processing (FSP) and Submerged Friction Stir Processing (SFSP) techniques. The properties of composite materials were analyzed using XRD, scanning electron microscopy, microhardness tester, and tensile testing machine. The experimental results show that both FSP and SFSP successfully prepared composite materials with high-entropy alloy particles uniformly distributed in the 5083 aluminum alloy matrix. Compared with FSP process, the HEA/Al composite material prepared by SFSP process has a more uniform and dense distribution of high entropy alloy particles, a smaller interface reaction layer thickness （about 150~200 nm）, no obvious reaction products generated at the interface, and a finer grain structure. Compared with the composite materials prepared by FSP process, the composite materials prepared by SFSP have better strength and plasticity, and the fracture surface has ductile fracture characteristics without obvious particle pull-out features. Compared to the 5083 Al matrix, the hardness of SFSFed HEA/Al composite material increases by 69.6% and the wear rate decreases by 48.2%.
In order to investigate the effect of laser power on the organization and properties of iron-based alloys, iron-based alloy coatings were prepared on the surface of 45 steel using laser cladding technology, and the specimens were analytically characterized through microstructure observation, hardness experiments, and electrochemical tests to study the effect of different laser powers (1 100, 1 400, 1 700, and 2 000 W) on the organization and properties of iron-based alloy coatings. The results show that the coatings prepared with different laser powers have no defects such as porosity and cracks, and are well combined with the substrate. The phase composition of the coating mainly consists of α-Fe, γ-(Fe,Ni), α-(Fe-Cr), and γ-(Ni-Cr-Fe) phases. With the increase of laser power, the dilution rate of the coating increases, the equiaxed grains also increase gradually, and the hardness tends to increase first and then decrease. When the laser power is 1 400 W, the coating hardness is 565.4 HV0.2 at maximum, Ecorr is -0.339 V at maximum, icorr is 3.19×10-6 A·cm-2 at minimum, and Rct is 71.8 kΩ at maximum, with the best corrosion resistance.
The energy density of traction Li-ion battery is its most important performance index. The metal lithium anode possesses ultra-high theoretical capacity (3 860 mAh/g) and ultra-low reduction potential (-3.04 V H+/H), and the energy density of the battery can be greatly improved by replacing the graphite anode. However, the biggest problem metal lithium anode suffer from is the electrochemical instability with the electrolyte, which result in intensified side reactions, the consumption electrolyte and the increasing the capacity decay. In addition, the growth of lithium dendrites caused by side reactions at the interface also increases the safety hazard and restricts the development of lithium metal batteries. To solve the as mentioned problems, in this study, magnetron sputtering method is used to deposit lithium phosphate (Li3PO4) as an artificial solid electrolyte interphase on the surface of lithium metal anode, so as to obtain high electrochemical stability of the lithium metal/electrolyte interface, and effectively inhibits the polarization of the battery. At the same time, the growth of lithium dendrites is also inhibited due to the increased lithium plating and stripping uniformity. With the modification of Li3PO4, which is ionic conductive and electron blocking, the time-constant mode critical circuit density increases from 1.6 mA/cm2 to 3.6 mA/cm2, and the capacity-constant mode critical circuit density increases from 4.0 mA/cm2 to 8.6 mA/cm2. The assembled pouch battery achieves an energy density of 355 Wh/kg and a capacity retention rate of 90.8% after 150 cycles at 0.2 C.
AlxCu1-xCoFeNi high entropy alloys (x=0.25, 0.5, and 0.75) were prepared using a combination of mechanical alloying and spark plasma sintering methods. The phase composition, microstructure, and mechanical properties of the high entropy alloy powder and sintered specimens at different stoichiometric ratios were studied. The results show that the sintered AlxCu1-xCoFeNi high entropy alloy with a ball milling time of 64 hours forms a single face centered cubic solid solution when x=0.25 and 0.5, while the high entropy alloy forms a face centered cubic and body centered cubic solid solution structure when x=0.75. At x=0.25, 0.5, and 0.75, the densities of the sintered AlxCu1-xCoFeNi high entropy alloy specimens are 98.3%, 95.8%, and 97.7%, respectively. At x=0.25 and 0.5, there is segregation of Al and Cu elements in the AlxCu1-xCoFeNi high entropy alloy, while at x=0.75, there is segregation of Al elements and no obvious segregation of Cu elements in the high entropy alloy. As the value of x increases from 0.25 to 0.75, the yield strength, fracture strength, and hardness of AlxCu1-xCoFeNi high entropy alloy gradually increase, while the compressive strain gradually decreases. Compared with cast AlCuCoFeNi high entropy alloy, the yield strength, fracture strength, compressive strain, and hardness of high entropy alloy are higher at x=0.25.
The combustible metal aluminum powder which is generated at the production and processing process in the industrial and trade industry has a greater risk of explosion. Building a combustion and explosion characteristics system of aluminum powder will help provide the key data support for the prevention and control of aluminum dust explosions. This review systematically discussed the experimental methods and results of aluminum powder flame speed, flame temperature, ignition sensitivity, and maximum explosion pressure, and then provided the commonalities and differences in the conclusions of aluminum powder combustion and explosion research and explored different experiments factors affecting the results. Finally, the evolution rules of the combustion and explosion characteristics of aluminum powder under different influencing factors were discussed.
With the rapid development of new energy vehicles, communications, and other technologies, there is an increasing demand for high-performance pure copper radiators with complex structures. Traditional forging, casting, powder metallurgy pressing and other processes are difficult to manufacture complex structure products, while machining, 3D printing and other processes are more costly, not easy to promote on a large scale, the metal powder injection molding process has the advantage of low-cost, batch manufacturing of complex shaped products, and is expected to realize the complex structure of the scale manufacturing of pure copper radiator. At present, the pure copper powder injection molding process faces technical challenges such as high cost of spherical powder and low sintered density. Therefore, this paper systematically summarized the research progress of pure copper powder injection molding process, focused on the research status of key processes such as feedstock preparation, injection molding, debinding and sintering, and put forward suggestions for future development, in order to provide references for advancing the engineering application of pure copper injection molding process.
Based on the reduction reaction and thermodynamic model, a systematic analysis was conducted on the thermal energy consumption and structural composition of the two-stage reduction process of molybdenum powder using a horizontal four-tube furnace as the reduction equipment. The results show that the heat consumed in the reaction process accounts for 17.87%, while the heat carried away by the excess reaction gas accounts for 68.54%. From the perspective of energy consumption management, energy consumption management strategies for the two-stage reduction process of molybdenum powder were proposed from three aspects: thermal efficiency improvement, heat loss control, and thermal effect assurance. Firstly, the thermal efficiency is improved through precise regulation of the hydrogen atmosphere in the reduction furnace; secondly, heat loss is reduced by combining equipment inspection with waste heat recovery and utilization; thirdly, the thermal effect is ensured by optimizing the equipment temperature control and data monitoring system. These multiple measures provide directions for equipment transformation and process optimization.
