Superplastic forming of titanium alloys is a new technology developed by utilizing the excellent deformation properties of materials in superplastic state.

Titanium alloys have superplasticity. TC4 (Ti6Al4V) is considered to be the most promising structural titanium alloys because of its excellent superplasticity. It has achieved rapid development and good economic benefits in the research and application of superplastic forming technology of structural titanium alloys. Compared with other titanium-based alloys, TC4 has the best superplasticity. It is widely used and mature. TC4 is the most widely used superplastic titanium alloy, so it is of practical significance to study the mechanical properties of this material after superplastic forming.

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The ductility of titanium alloy TC4 is relatively low at room temperature, but it has high ductility at high temperature. High temperature oxidation is one of the main factors affecting the Superplasticity of TC4. Although the oxidation resistance of TC4 is good, the oxidation film on the surface of titanium alloy TC4 can be formed at 800 ~900 ~C, which will cause cracks and reduce the ductility of titanium alloy. In order to prevent oxidation of titanium alloy during high temperature forming, in many cases, it is carried out under the protection of Ar. Although this method can protect titanium alloy from oxidation during superplasticity, it requires complex equipment and greatly increases the cost of process. Structural ceramics are superior to metals in chemical corrosion resistance, high hardness and wear resistance, high melting point temperature and high temperature strength, but toughening of structural ceramics has always been the most challenging subject in the field of ceramics. In order to improve the Superplasticity of superplastic titanium alloys, plasma spraying of ceramic powders was carried out to obtain a protective coating with high temperature resistance, oxidation resistance and superplastic deformation ability on the surface of superplastic titanium alloys.

At present, the basic heat treatment processes of titanium and titanium alloys are stress relief annealing, complete annealing, solid solution and aging treatment. Other processes, such as isothermal treatment, multi-stage annealing and multi-stage aging, are rarely used in production.

1. Solid solution and aging treatment process

Solid solution and aging treatment are actually divided into two steps: solid solution treatment and aging treatment. Solution treatment is the operation of heating, holding and rapidly cooling titanium rods and alloys to room temperature. Aging treatment is the operation of air-cooling after solid solution treatment and holding the workpiece for a certain time. The purpose of solution and aging treatment is that some a-Ti alloys, beta-Ti alloys and a+beta-Ti alloys can not be strengthened by heat treatment, but can only be strengthened by annealing to further strengthen their mechanical properties.

2. Stress relief annealing process

Stress relief annealing is also called incomplete annealing. Its function is to eliminate or reduce the internal stress produced during cold working and to prevent chemical erosion and deformation of workpiece in special environment.

3. Complete annealing process

The purpose of complete annealing of titanium and titanium alloys is to obtain stable metallographic structure and improve physical properties, which is conducive to reprocessing and improving the stability of workpiece size and properties.

In magnetron sputtering process, titanium target is one of the most commonly used targets. Titanium target not only has good adhesion, but also can make a variety of beautiful colors by using titanium target and appropriate reaction gas. Let me pick up all the characteristics and advantages of titanium. 1.First of all, it is certain that titanium target can make many kinds of colors, such as titanium gray, gun gray, black, imitation gold, coffee, blue, purple and so on. What new colors can you add? 2.Secondly, titanium has good adhesion to ceramic and glass substrates, so titanium can be used as a substrate material with poor adhesion. Titanium can also be used as a material for thin film resistors or thin film capacitors.

3.Titanium adsorbs active gases (such as CO, CO, CO 2, N2, O 2 and water vapor above 650 C) very strongly. Fresh Ti film evaporated on the mercury wall forms a surface with high adsorption capacity. It has excellent adsorption performance and can react with almost all gases except inert gases. This property makes Ti widely used as getter in ultra-high vacuum pumping system, such as Ti sublimation pump and sputtering ion pump.

4.Corrosion resistance. Titanium is a very active metal with low equilibrium potential and high thermodynamic corrosion tendency in medium. But in fact, titanium is very stable in many media, such as oxidizing, neutral and weak reductive media. This is because titanium and oxygen have a great affinity. In air or medium containing oxygen, a dense, strong adhesion and inert oxide film is formed on the surface of titanium, which protects the titanium matrix from corrosion. Even due to mechanical wear, it can quickly self-heal or regenerate. This indicates that titanium is a metal with strong passivation tendency. Titanium oxide film at medium temperature below 315 C always maintains this characteristic. Titanium has metallic luster and ductility. The density is 4.5 g/cubic centimeter. The melting point is 1660 +10. Boiling point 3287 C. Chemical valence + 2, +3 and + 4. The ionization energy is 6.82 electron volts. Titanium is characterized by low density, high mechanical strength and easy processing. The plasticity of titanium depends mainly on its purity. The more pure titanium is, the greater the plasticity is. It has good corrosion resistance and is not affected by atmosphere and sea water. At room temperature, it will not be corroded by hydrochloric acid under 7%, sulfuric acid below 5%, nitric acid, aqua regia or dilute alkali solution; only hydrofluoric acid, concentrated hydrochloric acid, concentrated sulfuric acid can act on it.

5.Titanium is biophilic. In the human body, it can resist the corrosion of secretions and is non-toxic. It is suitable for any sterilization method. Therefore, it is widely used to make medical instruments, artificial hip joint, knee joint, shoulder joint, hypochondriac joint, skull, active heart valve, bone fixation clip. When new muscle fibrous rings are wrapped in these “titanium bones”, these titanium bones begin to maintain the normal activities of the human body. Titanium is a non-magnetic metal, and will not be magnetized in a large magnetic field. It is non-toxic and has good compatibility with human tissues and blood, so it is adopted by the medical profession.

6. Good heat resistance and low temperature resistance.

The new titanium alloy can be used for a long time at 600 C or higher. Low temperature titanium alloys, such as titanium alloy TA7 (Ti-5Al-2.5Sn), TC4 (Ti-6Al-4V) and Ti-2.5Zr-1.5Mo, have higher strength with lower temperature, but less plastic change. It is an ideal material for cryogenic containers, tanks and other equipment to maintain good ductility and toughness at low temperatures of – 196 – 253, avoiding cold brittleness of metals.

7. Strong Anti-Damping Performance

Compared with steel and copper, titanium has the longest vibration attenuation time when it is subjected to mechanical and electrical vibration. This property of titanium can be used as vibration element of tuning fork, medical ultrasonic pulverizer and vibration film of advanced loudspeaker.

8. Tensile strength is close to yield strength.

This property of titanium shows that its yield strength ratio (tensile strength/yield strength) is high, which indicates that the plastic deformation of titanium metal is poor during forming. Because the ratio of yield limit to elastic modulus of titanium is large, the resilience of titanium during forming is great.

9. Good heat transfer performance

Although the thermal conductivity of titanium metal is lower than that of carbon steel and copper, its wall thickness can be greatly reduced due to its excellent corrosion resistance, and the heat transfer mode between surface and steam is dropwise condensation, which reduces the heat group, and the thermal resistance of titanium surface can be reduced without scaling, thus the heat transfer performance of titanium can be significantly improved.

10. Low modulus of elasticity

The elastic modulus of titanium at room temperature is 106.4 Pa, which is 57% of that of steel.

Titanium alloy is a kind of difficult-to-process material with poor thermal conductivity, easy to adhere to tools, strong notch sensitivity and strong work hardening during rolling. In actual production, there are a series of problems in rolling full teeth. Firstly, after filling the gap between the two rollers in the rolling process, if the rollers continue to roll, the blank material can not flow and can only be extruded back and forth between the rollers, resulting in higher surface hardening of the threads. When the hardening exceeds the tensile limit of the material, cracks occur. The hardening of the side and bottom of the threads is the most serious, so cracks occur. Secondly, when full extrusion, every tooth of the roller involved in rolling is also affected by strong cyclic load, and the energy of rolling also acts on the roller, so that its life is seriously reduced. In actual production, each roller can only roll 3000-5000 titanium bolts, resulting in the phenomenon of crown fragmentation. The roller can no longer be used, and the cost is extremely expensive. The cracking of the top of the roller tooth has a forming process, which makes it impossible for the producer to determine the eligibility of the rolling thread, that is, when the rolling is qualified and when the rolling is unqualified; thirdly, in the process of rolling forming the thread, the two sides rise fastest, which is bound to produce a fold on the top of the tooth when the thread is full, and there are fluorescent marks on the top of the thread during flaw detection, in order to determine the maximum. The depth of defect still needs to be determined by anatomical method. Fourthly, modern fastener joints have higher fatigue life and higher accuracy requirements for bolt holes. Hole wall damage is not allowed in the installation process, and the top of the more pointed thread is very easy to damage the hole wall. In a word, full thread profile brings great trouble to production. It not only increases the chance of cracking, decreases the fatigue life of parts, but also reduces the service life of the roller. Moreover, it brings unnecessary trouble to testing, and also easily causes damage to the hole wall. Therefore, it is imperative to correct the thread diameter of titanium alloy fasteners.

In foreign countries, such as all the titanium bolts in the United States and the latest standard of titanium bolts, the thread diameter has been revised, the thread size has been moved down, and the thread has adopted the unsaturated tooth type. In order to confirm this viewpoint and to provide a basis for the correction of the thread diameter of titanium alloy fasteners in China, the mechanical properties of two representative hexagonal head titanium bolts, HB6563.6 and HB6563.10, with different thread diameters, were tested. Two kinds of bolts are adopted three kinds of large diameter size, and mechanical performance verification includes tensile, fatigue and stress endurance test.

Pure titanium reaches 800,000 pounds/inch 2 (5517 MPa) and alloy titanium reaches 180,000 pounds/inch 2 (1241 MPa), which is far higher than the strength of many alloy steels, so titanium has a high strength-weight ratio. Titanium has twice the elasticity of steel and is an ideal choice for applications requiring high fracture or fracture resistance. In addition, titanium alloy has higher corrosion resistance and oxidation resistance than stainless steel. Many properties of titanium make it suitable for most applications, but at the same time lead to its becoming one of the most difficult materials to process. However, a manufacturer who understands the characteristics of this material can successfully process titanium parts without having to pay a high price. Most titanium alloys have poor thermal conductivity. The heat generated in the machining process does not diffuse through the parts and machine tool structure, but concentrates in the cutting area. In some cases, the temperature reached as high as 2,0000 F (11093 C) may lead to edge collapse and deformation, while the blunt edge will generate even higher heat and further reduce tool life. Cutting temperatures can be so high that titanium chips sometimes burst into flames. The high temperature produced in the cutting process will also cause the workpiece to harden continuously, which will affect the surface integrity of titanium, and may lead to inaccurate geometric accuracy of parts, and seriously reduce their fatigue strength. The elasticity of titanium alloys, which is beneficial and necessary for the product, adds fuel to the deflection and vibration in heavy load cutting. Under cutting pressure, “elastic” material is removed from the tool. Therefore, instead of cutting, the cutting edge rubs, especially when the feed is small. This friction process also generates heat, aggravating problems caused by poor thermal conductivity of materials.

The forward cutting geometry is adopted to reduce cutting force, heat and part deflection. Constant feed is used to prevent work hardening. Never stop feeding in the cutting process. Use a large amount of coolant to maintain thermal stability and prevent temperature rise problems that may lead to irregular secondary surfaces and possible tool failures. Keep the tool sharp. The blunt knife will accelerate the temperature rise and cause the wear and tear phenomena which lead to the failure of the knife. Processing titanium alloys in as soft a state as possible. Because many alloys are age-hardened — they harden when heated — they become stronger and more abrasive when forming second-phase particles. As far as possible, larger radius of tool end or circular blade are used to make the tool enter the cutting more. This reduces the cutting force at any point and prevents local damage.

In recent years, titanium alloy screw more and more attention and sought after by the market? Here comes a detailed understanding of it.

Being able to receive such attention from the market is bound to attract consumers, so to understand the reason for market attention is to understand the advantages of titanium alloy screw.

Of course, in previous articles, we all know about the advantages of titanium alloy screw, such as high temperature resistance of titanium alloy screw, acid and alkali resistance of titanium alloy screw, as well as its high hardness compared with other ordinary fasteners and so on.

Reasons for Low Temperature Resistance of Titanium Alloy Screws and Related Performance

Today, We wants to know with you about the low temperature resistance of titanium alloy screw, many people do not know, in fact, in terms of low temperature resistance, titanium alloy screw has a very strong advantage, of course, such ability can not appear without reason, the reason why titanium alloy screw can have a strong low temperature resistance is mainly due to its very low gap elements.

Titanium alloy screw can work normally even in the working environment of about 250 degrees below zero, and can keep its shape unchanged. However, most metals do not have such ability in such working environment.

Titanium alloy screw has excellent low temperature and high temperature resistance, but its ability to attract consumers is not only this, the following is about the titanium alloy screw has good thermoplasticity, and poor stamping performance!

I believe that in the future, titanium alloy screw will inevitably become the mainstream of the screw industry, after all, its powerful performance has far exceeded other metal screw in the same industry!