4. HVA-2 is a sulfur-free vulcanizing agent. It can replace all slag-containing vulcanizing agents such as those in cable rubber, and solves the problem of copper wire and copper electrical appliances being polluted by sulfur generated by connecting sulfur.
If you have any technical questions about HVA-2 ,pls contact us!
N,N'-(4,4'-diphenylmethane)bismaleimide is an aromatic bismaleimide resin known for its excellent high temperature resistance and mechanical properties. It is a high melting point yellow powder with strong chemical resistance.In the electronics field, BMI resins manufactured by Yangchen tech is used to make heat-resistant laminates and electrical insulation materials for harsh conditions (H/F grades).
In contrast, traditional epoxy resins are widely used in PCB laminates and adhesives due to their low cost and ease of use, but they begin to lose strength and degrade at high temperatures. This blog compares the material properties and application differences of 4,4′-bismaleimide (BMI) and epoxy resins in electronic devices.
The rigid, highly conjugated structure of N,N'-(4,4'-diphenylmethane) bismaleimide gives it a high melting point (about 150-160°C) and glass transition temperature. It is almost insoluble in water/ethanol, but soluble in polar organic solvents such as acetone or DMF. High curing temperatures (usually 200-250°C) make BMI crosslinked into a dense three-dimensional network structure with excellent thermal stability.Commercial systems usually mix BMI with vinyl or allyl comonomers (e.g. DABA, vinyl phenol) to improve toughness. Cured BMI is still harder and stronger than most epoxies at high temperatures.
Technical Indicators
| Appearance |
Melting point |
Acid value |
Volatile
|
Specification |
Gel time 200℃ |
Toluene Solubility |
| Yellow powder |
150-160℃ |
≤1mgKOH/g
|
≤1%
|
＞98%
|
＜300 S
|
Totally soluble or a small amount of insoluble matter, transparent solution
|
- The significant advantage of 4,4′-bismaleimide (BMI) resins is thermal stability. Unlike standard epoxy resins, which soften and lose modulus above about 120-150°C, BMI-based networks maintain mechanical integrity at temperatures well above 200°C.
- BMIs maintain strength and stiffness in high temperature environments (e.g., aerospace engines, gas turbines) where epoxies tend to fail.
- In fact, high-Tg BMI laminates or prepregs maintain excellent mechanical properties up to about 250°C.
- In contrast, most epoxy-based electronic materials have a Tg below 150°C, limiting them to low-grade insulation applications. BMI also has excellent mechanical strength and stiffness. Its rigid aromatic backbone gives it high tensile and flexural strength. Compared to epoxies, BMI composites can withstand greater static and dynamic loads without deformation.
- For example, parts made with a 4,4′-BMI matrix, such as aircraft fuselage panels or connector housings, will exhibit higher compression and impact resistance than equivalent epoxy-based parts. In tests, BMI composites have demonstrated improved durability under heavy loads and high-velocity impacts, thereby extending the service life and improving the safety of high-performance equipment.
- While epoxies are tough at room temperature, they tend to become brittle or creep at elevated temperatures, while the network rigidity of BMI remains strong. Another key advantage is its chemical and environmental resistance. BMI resins are more resistant to corrosion from solvents, acids, and other chemicals than typical epoxy formulations.
|
Property
|
4,4′-BMI (Bismaleimide Resin)
|
Epoxy Resin
|
|
Glass Transition (Tg)
|
>200 °C (often ~250 °C); stable mechanical/dielectric at high temps
|
~100–150 °C; mechanical properties degrade above ~120 °C
|
|
High-Temp Strength
|
Retains strength up to ~250 °C
|
Softens and may creep/fail well below 200 °C
|
|
Mechanical Modulus
|
Stiffer at all temperatures (especially when toughened)
|
Less stiff overall; can be toughened but weakens at high temp
|
|
Density
|
Lightweight vs. metal; potentially lighter than epoxy formulations
|
Lightweight vs. metal; but slightly denser than BMI in some cases
|
|
Thermal Conductivity
|
Poor conductor; can be filled for thermal applications
|
Poor conductor; also fillable with ceramics or carbon
|
|
Electrical Insulation
|
Meets Class F/H (155–180 °C); suitable for motors, coils, high-temp circuits
|
Often limited to Class B (130 °C); may not meet high-temp specs
|
|
Flame Rating
|
Inherently flame-retardant; low smoke/toxicity, fewer additives needed
|
Needs more additives for flame retardancy
|
The ideal characteristics of silver coated copper powder largely depend on the perfection and consistency of the silver coating at the microscopic level. High quality silver coated copper powder is a prerequisite for realizing its application value. The core goal and difficulty of the preparation process is to achieve uniform, dense, continuous, and thickness controllable silver layer coverage on the surface of copper powder particles. At present, the preparation methods of silver coated copper powder mainly include mechanical ball milling, melting spray, chemical plating, etc
01 Mechanical ball milling method
The mechanical ball milling method is to mix copper powder and silver powder in proportion and place them in a ball mill. By relying on the intense impact, friction, and cold welding effects generated by the high-speed rotating grinding ball, silver is forcibly squeezed, adhered, and cold welded to the surface of copper particles. The advantage of this method lies in its relatively simple equipment, concise process, high theoretical yield, and low cost, without involving complex chemical reactions or waste liquid treatment issues. However, the "silver layer" formed is essentially silver fragments or clumps mechanically attached and cold welded, making it difficult to achieve a uniform, continuous, pore free, and dense complete coating layer. There are problems with incomplete coverage, weak bonding force, and weak control over the coating morphology. To improve the coating effect of traditional ball milling methods, copper powder is generally shaped into flakes during the ball milling process, significantly increasing the contact area between copper powder and silver particles while shortening the diffusion path of silver atoms. This is conducive to the more effective diffusion of silver substances on the surface of copper sheets, ultimately forming silver coated copper sheets with stronger bonding force, relatively denser and more uniform coating. However, the mechanical ball milling method is prone to introducing wear impurities from the grinding balls and the tank body, posing potential challenges to the stability and long-term reliability of product performance.
02 Melting spray method
The melt atomization method is to atomize molten droplets containing copper and silver and solidify them under rapid cooling conditions. Due to the higher fluidity of silver compared to copper at higher temperatures (>900 ℃), it can migrate to the surface of copper particles and achieve coating of copper particles. Using this technology to prepare silver coated copper powder, its silver content is extremely low, but the surface silver content is very high, and the silver content gradually decreases from the surface to the interior, showing a ladder like distribution. However, the preparation process is relatively complex, the production cost is high, and it is not suitable for large-scale production.
03 Chemical plating method
Chemical silver plating is the process of reducing silver ions in a solution to elemental silver through an oxidation-reduction reaction, and depositing and coating it on the surface of a copper substrate. The advantages of chemical plating method are good uniform plating and deep plating ability, which can be applied to non-metallic and semiconductor materials. The equipment is simple and the operation is easy. It is currently the most widely used method for preparing silver coated copper powder. According to the sedimentation mechanism, chemical plating can be divided into two types: displacement method and reduction method:
① Substitution method
The displacement method utilizes the characteristic that the reduction potential of copper is lower than that of silver. When copper powder is immersed in a solution containing silver ions (Ag ⁺), an electrochemical displacement reaction occurs: 2Ag ⁺+Cu ->2Ag+Cu ² ⁺. Silver ions are reduced and deposited on the surface of copper powder, while copper atoms are oxidized into copper ions and enter the solution. However, due to the displacement reaction between copper powder and silver source, the copper powder is enveloped by silver coating, which hinders the progress of the displacement reaction. At the same time, the reaction rate between copper powder and silver source solution is fast, and the silver coating quickly deposits on the surface of the copper powder. Therefore, silver coated copper powder prepared by displacement method often has the problem of thin and loose coating, which affects its performance. Generally, chelating agents (such as ammonia water) can be added during the preparation process to reduce the reaction rate, allowing silver metal to slowly deposit on the surface of copper powder, or multiple silver plating can be used to improve the morphology and coating rate of silver coated copper powder.
② Restoration method
The reduction method uses reducing agents (such as formaldehyde, glucose, hydrazine hydrate, ascorbic acid) to reduce silver ions (Ag ⁺) in the solution to elemental silver and deposit it on the surface of copper powder. The reaction mechanism consists of two stages: firstly, due to the higher activity of copper (Cu) than silver (Ag), copper powder first undergoes a displacement reaction with Ag ⁺: 2Ag ⁺+Cu → 2Ag+Cu ² ⁺, forming a thin layer of silver on the copper surface. As the replacement silver layer covers the copper surface, it hinders direct contact between copper and Ag ⁺, and the replacement reaction stops. At this point, the Ag ⁺ in the solution mainly relies on the reducing agent to undergo a reaction (such as 2Ag ⁺+reducing agent → 2Ag+oxidation product), and silver continuously and uniformly deposits and thickens on the initial displacement layer, forming a denser silver coating layer.
SAT NANO is a best supplier of silver coated copper powder in China, we can supply nano particle size and micro particle size, if you have any enquiry, please feel free to contact us at admin@satnano.com
High-grade AlN powder is the cornerstone of the aluminum nitride industry, characterized by low oxygen content, high specific surface area, narrow particle size distribution, excellent sintering activity, and moisture resistance.
Oxygen Content in Powder
This is a critical indicator for high-grade AlN powder. The oxygen in AlN primarily comes from surface-adsorbed oxygen, existing as a mixture of Al₂O₃ and AlOOH coating the powder particles. During sintering, oxygen easily diffuses into the AlN lattice, forming structural defects such as aluminum vacancies. These defects scatter phonons, reducing their mean free path and ultimately degrading the material's thermal conductivity.
Specific Surface Area & Particle Size Distribution
Generally, as particle size decreases and specific surface area increases, the powder's surface energy rises, enhancing its reactivity and sintering driving force. The specific surface area, dispersibility, particle size, and distribution are key factors determining densification and the final performance of sintered products.
Other Impurities & Their Content
Besides oxygen, other impurities can dissolve into the AlN lattice, introducing defects that further reduce thermal conductivity.
Moisture Resistance
AlN powder is prone to hydrolysis in humid air, reacting with water vapor to form Al(OH)₃ and NH₃, as shown in Equation (1). The loose byproducts fail to protect the powder, leading to continuous oxidation and even deterioration. Therefore, AlN powder must be stored in a dry, sealed environment. To improve storage, transportation, and usability, surface modification can enhance its hydrolysis resistance.
AlN + 3H₂O → Al(OH)₃ + NH₃ (1)
Conclusion
With the advancement of semiconductors, aerospace, new energy, and 5G communications, thermal management in high-power and high-heat-flux devices has become a major challenge affecting performance and reliability. As a high-performance thermal conductive material, AlN is gaining broader applications.
About Xiamen Juci Technology Co., LTD
Xiamen Juci Technology Co., Ltd. is China's leading manufacturer of aluminum nitride (AlN) powder by production volume. Our high-purity aluminum nitride powder and customized AlN ceramic products deliver superior thermal conductivity and cost-effective performance, making them ideal for advanced thermal management applications.
We specialize in innovative thermal solutions tailored for industries such as 5G communications, semiconductors, new energy, and aerospace, helping clients achieve optimal heat dissipation and system reliability.
Media Contact:
Xiamen Juci Technology Co., Ltd.
Phone: +86 592 7080230
Email: miki_huang@chinajuci.com
Website: www.jucialnglobal.com
Disposable nursing pads are mainly made of the following raw materials:
PE film: PE film is polyethylene film, which has good waterproof properties and can effectively prevent liquid leakage. It is a common material for the bottom layer of nursing pads.
Non-woven fabric: Non-woven fabric is a material made by physically bonding fibers together. It has the characteristics of lightness, breathability, softness and skin-friendliness. In nursing pads, non-woven fabrics are often used in the surface and middle layers, providing good touch and breathability, and also helping the rapid penetration and distribution of liquids.
Fluff pulp: Fluff pulp is a kind of wood pulp or waste paper pulp that has been specially processed and has good water absorption and fluffiness. In nursing pads, fluff pulp is the main material of the absorption layer, which can quickly absorb and store liquids and keep the surface dry.
Polymer absorbent material: Polymer absorbent materials such as super absorbent resin (SAP) have super strong water absorption capacity, can absorb hundreds of times its own volume of water, and firmly lock the liquid to prevent leakage. This material serves as the core absorption layer in the nursing pad, ensuring that the product has excellent water absorption and liquid retention properties.
In addition, according to the specific product design and production process requirements, disposable nursing pads may also contain other auxiliary materials, such as elastic materials, hot melt adhesives, etc. These materials play the role of fixing, fitting, and bonding in the nursing pad, which helps to improve the comfort and use effect of the product.
In summary, the raw materials of disposable nursing pads mainly include PE film, non-woven fabrics, fluff pulp and polymer absorbent materials, etc., which together constitute the structural and functional basis of the nursing pad.
For more information, please click www.glinknonwoven.com
Aluminum nitride (AlN) substrates possess ultra-high thermal conductivity, excellent electrical insulation, and thermal expansion properties similar to semiconductor materials like silicon wafers, making them widely applicable in the electronics packaging industry.
The market leader in China for raw aluminum nitride powder is Xiamen Juci Technology Co., Ltd., with an annual production capacity of 700 tons of AlN powder. Xiamen Juci Technology primarily employs the carbothermal reduction method to produce high-purity electronic-grade aluminum nitride powder. The advantage of the carbothermal reduction method is its ability to utilize a wide range of raw materials (Al₂O₃) while maintaining stable process control.
The principle of the carbothermal reduction process involves heating a uniformly mixed blend of Al₂O₃ and carbon in a nitrogen atmosphere. First, Al₂O₃ is reduced, and the resulting aluminum reacts with nitrogen to form AlN. The chemical reaction is as follows: Al₂O₃(s) + 3C(s) + N₂(g) → 2AlN(s) + 3CO(g). This method is simple, yields high-purity powder with small and uniformly distributed particle sizes, but requires a long synthesis time and high nitridation temperatures. Additionally, excess carbon must be removed after the reaction. Incomplete carbon removal leads to excessive residual carbon content in the aluminum nitride powder, which significantly impacts its performance.
Excessive residual carbon content primarily affects aluminum nitride ceramics in the following ways:
1. Impact on the Sintering Process
During the sintering of aluminum nitride ceramics, residual carbon content influences the densification and microstructure of the sintered body. Excessive residual carbon may lead to the formation of pores or cracks in the sintered body, thereby reducing the material's mechanical properties and thermal stability.
2. Impact on Thermal Conductivity
The presence of residual carbon directly affects the thermal conductivity of aluminum nitride ceramics. Since carbon has much lower thermal conductivity than aluminum nitride, an increase in residual carbon content will reduce the overall thermal conductivity of the ceramic.
3. Impact on Mechanical Properties
Residual carbon content also affects the mechanical properties of aluminum nitride ceramics, such as flexural strength and fracture toughness. Experimental studies have shown that as temperature decreases, aluminum nitride ceramics with an appropriate amount of residual carbon exhibit improved flexural strength and fracture toughness. However, excessively high residual carbon content may lead to internal stress concentration, thereby degrading mechanical performance.
4. Impact on Electrical Properties
For applications requiring high electrical insulation, the presence of residual carbon may reduce the electrical insulation performance of aluminum nitride ceramics. Since carbon is inherently conductive, excessive residual carbon content increases the material's electrical conductivity, negatively impacting its use in electronic applications.
About Xiamen Juci Technology Co., LTD
Xiamen Juci Technology Co., Ltd. is the leading manufacturer of aluminum nitride powder in China in terms of output. The aluminum nitride powder and customized ceramics produced by Xiamen Juci Technology Co., Ltd. feature higher thermal conductivity and more competitive prices. We are committed to providing customers with advanced thermal management technologies and offering effective thermal management solutions for industries such as 5G, semiconductors, new energy, aerospace, etc.
Media Contact:
Xiamen Juci Technology Co., Ltd.
Phone: +86 592 7080230
Email: miki_huang@chinajuci.com
Website: www.jucialnglobal.com
Application Background
The cow leg separator is a ground-mounted component used in modern milking parlors to gently guide dairy cows into a stable stance, automatically separating their hind legs to facilitate milking.
This device often features mounting holes for spray nozzles, allowing for automated cleaning or sanitizing of the udder and legs using water or disinfectant spray.
Previously, the separator was typically made from short glass fiber reinforced plastic.
However, under repeated load, hoof impact, and exposure to harsh farm environments—such as manure, moisture, and cleaning chemicals—short fiber materials often suffered from insufficient strength, deformation, cracking, or premature aging.
Material Upgrade
Advantages of PA6 Long Glass Fiber 30% (LGF-PA6)
• High Load-Bearing Strength
PA6 reinforced with 30% long glass fiber (LGF-PA6) forms an internal continuous-fiber skeleton during molding, significantly boosting mechanical strength. This allows the separator to safely withstand the full bodyweight of cows stepping or standing on it without deformation or breakage, ensuring safety and long-term structural stability.
• Excellent Chemical Resistance
Farm environments expose equipment to a mix of urine, feces, disinfectants, and detergents. LGF-PA6 exhibits strong resistance to chemical corrosion and environmental degradation, maintaining its integrity and mechanical properties over time—critical for hygienic and durable milking operations.
• Superior Impact and Fatigue Performance
Unlike short fiber composites, LGF-PA6 offers enhanced fatigue durability, effectively handling daily stress from cow movement, hoof impact, and vibrations without cracking or weakening, reducing maintenance and replacement costs.
• Dimensional Stability and Clean Finish
With reduced shrinkage and warping during injection molding, LGF-PA6 ensures tight dimensional tolerances for secure fitting of spray system components. The smooth molded surface enhances appearance, reduces dirt buildup, and simplifies cleaning, supporting farm hygiene standards.
Performance Comparison
Property
|
PA6 Short Glass Fiber
|
PA6 Long Glass Fiber
|
Load Strength
|
Moderate
|
High – supports cow stepping
|
|
Durability
|
Prone to cracking
|
Excellent fatigue resistance
|
|
Stability
|
Shrink/warp risk
|
Stable and precise
|
Chemical Resistance
|
Limited
|
Resistant to farm chemicals
|
Surface
|
Rough, traps dirt
|
Smooth, easy to clean
|
Processing
|
Standard
|
Efficient, no post-treatment
|
PA6 reinforced with 30% long glass fiber
Ready to Upgrade Your Milking Equipment?
Discover how PA6 Long Glass Fiber 30% can deliver the strength, durability, and chemical resistance your cow leg separators and other agricultural components demand.
Whether you're improving existing parts or developing new equipment, our material experts are here to support you with tailored solutions.
Contact us today to request samples, technical data, or discuss how long fiber thermoplastics can enhance your product performance across a range of agricultural applications.
The essence of sintering is that the powder block is heated in an appropriate environment or atmosphere, and through a series of physical and chemical changes, the bonding between powder particles undergoes a qualitative change. The strength and density of the block increase rapidly, and other physical and mechanical properties are also significantly improved. The performance of ceramic materials is not only related to their chemical composition, but also closely related to their microstructure. After the formulation, mixing, forming and other processes are completed, sintering is the key process to obtain the expected microstructure of the material and endow it with various properties.
Sintering is a process that reduces pores in the formed body, increases the bonding between particles, and improves mechanical strength. During the sintering process, as the temperature increases and the heat treatment time prolongs, the number of pores decreases and the bonding force between particles increases. When a certain temperature and heat treatment time are reached, the grain size increases and the mechanical strength decreases. According to thermodynamic principles, sintering is a process in which the total energy of a system is reduced. Compared to bulk materials, powders have a large specific surface area, and surface atoms have much higher energy than internal atoms. At the same time, various lattice defects also exist inside the powder particles during the manufacturing process. Any system has a tendency to transition to the lowest energy state, which is the driving force of the sintering process, that is, the transition from the compact to the sintered compact is the process of the system transitioning from a metastable state to a stable state.
However, sintering generally cannot be carried out automatically because its inherent energy cannot overcome the energy barrier and must be heated to a certain temperature before it can proceed. Sintering is a complex process of physical and chemical changes. After long-term research, the sintering mechanism can be summarized as follows: ① fluidity, ② evaporation and agglomeration; ③ Volume diffusion; ④ Surface diffusion: grain boundary diffusion; Plastic flow, etc. Practice has proven that it is difficult to explain all sintering processes using any single mechanism. Sintering is a complex process that is the result of the interaction of multiple mechanisms. During the sintering process, the main changes occur in the size and shape of grains and pores. Taking the sintering process of Al2O3 ceramics as an example to illustrate the sintering process of ceramic materials: Al2O3 ceramics generally contain several tens of percent of pores during growth and failure, and there is only point contact between particles. Under the driving force of reduced surface energy, the substance fills the neck and pore areas between particles through different diffusion pathways, causing the neck to gradually grow and the volume occupied by the pores to gradually decrease. Grain boundaries gradually form between small particles, and the area of the grain boundaries continues to expand, making the body denser. During this considerable process, the connected pores continuously shrink, and the grain boundaries between two particles meet adjacent grain boundaries, forming a grain boundary network: the grain boundaries move and the grains gradually grow. The result is a reduction in porosity and an increase in densification, until the pores are no longer connected to each other, forming isolated pores distributed at the intersection of several grains.
At this point, the density of the green body reaches over 90% of the theoretical density, and the early stage of sintering ends here. Continuing into the later stage of sintering, isolated pores diffuse to the grain boundaries to eliminate them, or in other words, substances on the grain boundaries continue to diffuse and fill the pores, allowing densification to continue while the grains continue to grow uniformly. Generally, pores move along with grain boundaries until densification occurs, resulting in a dense ceramic material. If sintering continues at high temperatures thereafter, it will be a simple process of grain boundary movement and grain growth. The growth of the grain boundary is not the mutual bonding of small particles, but the result of grain boundary movement. The movement of grain boundaries with different shapes varies. Curved grain boundaries always move towards the center of curvature. The smaller the curvature radius, the faster the movement. During the grain growth process in the later stage of sintering, there may be a phenomenon where the migration rate of pores is significantly lower than that of grain boundaries. At this time, pores detach from the grain boundaries and are wrapped inside the grains. Subsequently, due to factors such as the lengthening of the material diffusion path and the decrease in diffusion rate, it became almost impossible to continue with the further reduction and elimination of pores. In this case, further sintering is difficult to improve the degree of densification, but the grain size will continue to grow, and even abnormal growth of a few grains may occur, causing more residual small pores to be trapped deep in the larger grains.
After sintering, the macroscopic changes of Al2O3 ∝ ceramic body are: volume shrinkage, density increase, and strength increase. Therefore, the degree of sintering can be measured by indicators such as the shrinkage rate, porosity, or the ratio of bulk density to theoretical density of the green body.
The sintering of ceramics can be divided into solid-phase sintering and liquid-phase sintering. High purity substances usually do not exhibit liquid phase at sintering temperature and belong to solid-state sintering. For example, high-purity oxide structured ceramics are mostly sintered into ceramics through solid-state sintering. And some often have liquid phase during sintering, which belongs to liquid-phase sintering. In addition, sintering can be divided into two categories based on the presence or absence of external pressure: pressureless sintering and pressure sintering. Pressure sintering, also commonly known as hot pressing sintering.
Pure oxide or compound powders are formed into green bodies with only point contacts between particles, resulting in low strength. However, through sintering, although there is no external force or chemical reaction during sintering, the particles in point contact can tightly bond into a hard and high-strength ceramic body, driven by the surface energy of the powder particles.
SAT NANO is a best supplier of sintering material in China, we can offer Al2O3 nanopowder, ZrO2 nanopowder, and MgO nanopowder for sintering, if you need other materials for sintering, please feel free to contact us at admin@satnano.com
The composition of TC4 titanium alloy is Ti-6AI-4V, which belongs to the (a+β) type titanium alloy. It has good comprehensive mechanical properties, high specific strength, excellent corrosion resistance, good biocompatibility, and is widely used in aerospace, petrochemical, biomedical and other fields. This article selects the plasma rotating electrode method to prepare titanium alloy powder, and discusses the spheroidization mechanism of titanium alloy powder. The evolution law of its microstructure is explored, and the main heat treatment methods are discussed, providing necessary theoretical basis for the application of TC4 titanium alloy in 3D printing technology.
2.1 Experimental Materials and Methods: TC4 alloy powder was prepared by plasma rotating electrode atomization method, and its chemical composition was analyzed by instruments, as shown below.
|
Al
|
Fe
|
V
|
C
|
N
|
Si
|
O
|
H
|
Ti
|
|
6.25
|
0.27
|
3.92
|
0.1
|
0.006
|
0.10
|
0.12
|
0.005
|
89.23
|
According to the table, the H, N, and O content in the powder is relatively low, which meets the requirements for printing high-performance products. The shape of the powder particles prepared by this process is very close to spherical, with a smooth surface, good flowability, and no excessive impurities. The SEM image observed under a scanning electron microscope is shown in Figure 1, and the individual powder particles are shown in Figure 2. Through observation, when the geometric shape of TC4 titanium alloy powder particles is spherical, the formability is good, while elliptical powder has poor flowability and formability. Spherical titanium alloy powder has good flowability during laser 3D printing preparation.
2.2 Experimental Results and Analysis 2.2.1 Ball Forming Mechanism of TC4 Titanium Alloy Powder In 3D printing technology, metal powder material is the raw material for metal 3D printing, and its basic properties have a significant impact on the quality of the final product formation. It is also one of the material basis and key elements for achieving rapid prototyping. The TC4 alloy powder prepared by plasma rotating electrode atomization method has a particle shape that is very close to spherical, with a smooth surface and good flowability. The mechanism of powder balling mainly consists of three processes, as shown in Figure 3. In the first process, the molten alloy droplets are impacted by high-speed airflow, causing them to grow into a wavy liquid film and move away from the gas center at high speed; In the second process, due to the pressure, the elongated alloy droplets are unstable. Under the surface tension of the liquid, they are then blown and broken, forming elliptical droplets; In the third process, the elliptical droplet continues to break again under the action of air pressure and liquid surface tension, and is segmented into several small droplets. Under the action of surface tension, the droplet tends to shrink into a spherical shape during the descent process, and the cooling accelerates, immediately solidifying into a spherical shape.
This experiment can obtain TC4 titanium alloy particle sizes mainly distributed in the range of 50-160 μ m by controlling the relevant parameters of the experiment. The particle size distribution is narrow and meets the requirements of 3D printing.
2.2.2 Microstructure of TC4 Titanium Alloy Sample The metallographic structure of the cross-section of the TC4 titanium alloy sample is shown in Figure 4. When the ion beam acts on the TC4 titanium alloy powder, a circular molten pool is formed. Within the molten pool, the temperature gradually decreases from the center to the edge, showing a Gaussian distribution. The difference in temperature results in varying degrees of melting of TC4 titanium alloy powder, with powders at lower temperatures in the edge region remaining unmelted or insufficiently melted, leading to differences in grain microstructure and size between the melt pool and the edge region. The use of pulse dot mode for metal powder cladding can reduce the influence of temperature gradient on the heat affected zone. When the latter heat source acts on the alloy powder, it also supplements energy to the edge area of the previous spot for remelting. After obtaining the energy, the grains continue to grow along the direction of energy absorption.
The metallographic structure photo of the longitudinal section of TC4 titanium alloy sample is shown in Figure 5. Through metallographic microscope observation, the microstructure is coarse β - columnar products. As shown in Figure 5, the grain boundaries can be clearly observed, and the columnar crystals grow along the stacking layer direction, with different growth directions. The growth stops at the β - columnar crystal boundary, and at the same time, the columnar crystals far away from the substrate continue to grow epitaxially, with grain growth phenomenon. After analysis, it was found that the temperature generated during the preparation of TC4 alloy by 3D printing has an impact on the microstructure of titanium alloy. When some of the alloy powder is melted by ion beam, the front part of the alloy is reheated. However, the beta phase self diffusion coefficient of TC4 alloy is relatively large, and smaller energy can promote grain growth. Therefore, columnar crystals are prone to growth and overheating during reheating.
Therefore, controlling the energy of the heat source can effectively alter the microstructure of TC4 alloy.
2.2.3 Solid solution and aging heat treatment Figure 6 shows the metallographic structure of TC4 alloy in three different heat treatment states: as deposited (a), 970 ° C/1h+540 ° C/4h (b), and 970 ° C/1h (c). The deposited TC4 alloy has a mixed microstructure of alpha solid solution and beta solid solution; After heat treatment at 970 ° C/1h+540 ° C/4h (b), the metallographic structure transformed into a mesh basket structure; After further heat treatment at 970 ° C/FC/1h (c), the structure transformed into a bimodal structure consisting of a basket like structure and spheroidized alpha phase. Among them, the high-temperature creep performance, strength, and plasticity of the basket structure are good, while the plasticity of the bimodal structure is low and the strength is high.
Through analysis, it is known that solid solution and aging heat treatment can effectively improve the strength and plasticity of TC4 titanium alloy, but the cooling rate has a significant impact on the strength and plasticity of TC4 titanium alloy, and appropriate cooling methods should be adopted in production.
Figure 7 shows the microscopic images of the microstructure of TC4 titanium alloy mesh basket under different cooling methods. When TC4 titanium alloy is air-cooled, a semi diffusion phase transformation occurs. After solid solution and aging treatment, the β phase solid solution between the primary α phase solid solution will appear as small secondary α phase solid solution, as shown in Figure 7 (a); When TC4 titanium alloy is cooled in a furnace, diffusion type phase transformation occurs. After solid solution treatment, a bimodal structure is formed. The β phase solid solution between the primary α phase solid solution in the alloy does not produce secondary α phase solid solution due to the lack of subsequent aging heat treatment, as shown in Figure 7 (b); By comparison, it can be seen that under furnace cooling conditions, the grain boundaries and intragranular alpha phase solid solution are coarser than under air cooling conditions. When TC4 titanium alloy is subjected to external forces, cracks are more likely to initiate and propagate at the grain boundaries, resulting in reduced plasticity, and printing molding is not utilized.
Summary: (1) TC4 titanium alloy powder prepared by plasma rotating electrode method, (Tianjiu Metal can customize TC4 titanium alloy powder with different processes according to customer needs), the powder particle shape is very close to spherical, the surface is smooth, the flowability is good, and it has good powder characteristics, which meets the requirements of 3D printing.
(2) The microstructure of the cross-section of TC4 titanium alloy shows radiating columnar crystals from the temperature center to the edge, while the microstructure of the longitudinal section shows columnar crystals growing along the stacking layer direction. The control of heat source energy can effectively improve the microstructure of TC4 titanium alloy.
(3) The heat treatment method of solid solution+aging and air cooling effectively improves the strength and plasticity of the deposited TC4 titanium alloy, making its performance meet the requirements of TC4 titanium alloy 3D printing.
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In recent years, with the rapid development of 3D printing technology, NiTi alloy powder has attracted much attention as a key raw material for biomedical implants. As the foundation of 3D printing, the quality of powder raw materials is crucial, and the plasma rotating electrode atomization method has attracted much attention.
Preparation method of plasma rotating electrode
The PREP method is used to prepare NiTi alloy powder, and the equipment mainly includes a rotary feed mechanism, an atomization chamber, a plasma gun device, and a feeding mechanism. Using NiTi alloy rods as raw materials, they are made into electrode rods and melted at high temperatures generated by plasma gun arcs. By utilizing the centrifugal force generated by the high-speed rotation of the electrode rod itself, melted metal is instantly ejected and rapidly solidified into spherical powder in a cooling medium. During the preparation process, high-purity argon gas is used as a protective gas with a purity of 4N (99.99%). By adjusting parameters such as plasma gun main current, spindle speed, and bar feed rate, the preparation conditions were optimized.
Powder characteristics
The powder particle size is mainly distributed between 60 and 125 μ m. Through scanning electron microscopy observation, it was found that the condensed tissue of larger particles (≥ 178 μ m) is a cellular crystal structure with poor surface smoothness; Small particles (≤ 40 μ m) have a smooth surface and no obvious crystalline structure.
Microstructure
The microstructure of powders with different particle sizes was observed by scanning electron microscopy and transmission electron microscopy. It was found that as the particle size decreased, the microstructure of the powder gradually refined, and the cellular crystal structure gradually disappeared, transforming into a finer equiaxed crystal structure. At the same time, more dislocations and twinning structures appeared in powders with smaller particle sizes, which had a significant impact on the phase transition behavior and mechanical properties of the powder.
The spherical NiTi alloy powder prepared by PREP method has the advantages of high sphericity, less hollow powder and satellite powder, and is very suitable as a raw material powder for 3D printing technology. The results of this study have important guiding significance for improving the performance of 3D printed products and optimizing 3D printing processes
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