What is Titanium Alloy?

Titanium is an important structural metal developed in the 1950s. Titanium alloys have high strength, good corrosion resistance and high heat resistance. In the 1950s and 1960s, it was mainly the development of high-temperature titanium alloys for aircraft engines and structural titanium alloys for airframes.

Titanium is an important structural metal developed in the 1950s. Titanium alloys are widely used in various fields because of their high strength, good corrosion resistance, and high heat resistance. Many countries in the world have realized the importance of titanium alloy materials, researched and developed them successively, and obtained practical applications.

The first practical titanium alloy was the Ti-6Al-4V alloy successfully developed in the United States in 1954. Due to its heat resistance, strength, plasticity, toughness, formability, weldability, corrosion resistance and biocompatibility Better, it has become the trump alloy in the titanium alloy industry, and the amount of the alloy used has already accounted for 75% to 85% of the total titanium alloy. Many other titanium alloys can be considered as a modification of Ti-6Al-4V alloy.

In the 1950s and 1960s, it was mainly the development of high-temperature titanium alloys for aircraft engines and structural titanium alloys for airframes. A number of corrosion-resistant titanium alloys were developed in the 1970s. Since the 1980s, corrosion-resistant titanium alloys and high-strength titanium alloys have been further developed. development of. The temperature of the heat-resistant titanium alloy has increased from 400 ° C in the 1950s to 600-650 ° C in the 1990s. The emergence of A2 (Ti3Al) and r (TiAl) -based alloys has made titanium in the use of the engine from the cold end (fan and compressor) of the engine to the hot end (turbine) of the engine. Structural titanium alloys develop in the direction of high strength, high plastic, high strength, high toughness, high modulus, and high damage tolerance.

In addition, since the 1970s, Ti-Ni, Ti-Ni-Fe, Ti-Ni-Nb, etc. have also appeared.

Titanium alloy is based on titanium

Titanium is a new type of metal. The performance of titanium is related to the impurity content of carbon, nitrogen, hydrogen, and oxygen. The purest titanium iodide impurity content does not exceed 0.1%, but its strength is low and its plasticity is high. 99.5%

Titanium alloy has high strength and small density, good mechanical properties, good toughness and corrosion resistance. In addition, titanium alloy

Common heat treatment methods include annealing, solid solution and aging treatment. Annealing is to eliminate internal stress, improve plasticity and microstructure stability, to obtain better comprehensive properties. Usually, the annealing temperature of alloy and ( + ) alloy is selected between ( + ) phase transition point 120 200 ; the solution and aging treatment is fast cooling from high temperature area to obtain

In the middle and after the heat treatment, surface treatment is mostly required to remove the oxide scale and various pollutants on the metal surface, reduce the activity of the bare metal surface, and apply a protective layer and various functional coatings on the surface halogen of titanium and its alloys. Surface treatment is also performed before and during the coating process. The coating is applied to improve the properties of the metal surface, for example, to prevent corrosion, oxidation and abrasion.

The pickling conditions of titanium and its alloys depend on the type (characteristics) of the oxide layer and the existing reaction layer, and the type of this layer is affected by the high temperature heating process and the increased temperature of the processing process (for example, forging, casting, welding, etc.) . Only a thin oxide layer is formed at a lower processing temperature or about 600X: below the heating temperature of high temperature. At high temperature, an oxygen-rich diffusion zone is formed near a certain oxide layer, which must also be eluted by acid. Remove this oxygen-rich diffusion layer. Various methods for descaling can be used: mechanical methods for removing thick oxide layers and hard surface layers, methods for removing scale in a molten salt bath, and method for removing the scale by acid elution in an acid solution.

In many cases, a combination of methods can be used, for example, mechanical scale removal and acid pickling, or salt bath and acid pickling. In the case of an oxide layer and a diffusion layer formed at a higher temperature, a special method is used, but the oxide layer formed under a high temperature of 600X: can be dissolved by ordinary pickling.

Titanium alloy has the advantages of light weight, high specific strength, and good corrosion resistance, so it is widely used in the automotive industry. The most widely used titanium alloy is automotive engine systems. There are many benefits to using titanium alloys to make engine parts. ^[1]

The main limitation of titanium and titanium alloys is the poor chemical reactivity with other materials at high temperatures. This property forces the titanium alloy to be different from the conventional traditional refining, melting and casting techniques, and often even causes damage to the mold; as a result, the price of the titanium alloy becomes very expensive. As a result, they were initially mostly used in aircraft structures, aircraft, and high-tech industries such as the petroleum and chemical industries. However, due to the development of space technology and the improvement of people's quality of life, titanium alloys have gradually been used to make people's livelihood products for the benefit of people's lives. However, the prices of these products are still high, and most of them are high-priced products. This is titanium alloy. The biggest fatal injury that cannot be carried forward.

Countries are developing low-cost and high-performance new titanium alloys, and strive to make titanium alloys enter the civilian industry with huge market potential. The new research progress of titanium alloy materials at home and abroad is mainly reflected in the following aspects.

High temperature titanium alloy

The first high-temperature titanium alloy successfully developed in the world is Ti-6Al-4V, with an operating temperature of 300-350 ° C. Subsequently, IMI550, BT3-1 and other alloys with a temperature of 400 ° C and IMI679, IMI685, Ti-6246, and Ti-6242 were used. New high-temperature titanium alloys that have been successfully used in military and civil aircraft engines are: British IMI829 and IMI834 alloys; American Ti-1100 alloys; Russian BT18Y and BT36 alloys. Table 7 shows the maximum use temperature of new high-temperature titanium alloys in some countries [26].

In recent years abroad, the development of titanium alloys using rapid solidification / powder metallurgy technology, fiber or particle-reinforced composite materials has been the development direction of high-temperature titanium alloys, so that the use temperature of titanium alloys can be increased above 650 ° C [1,27,29,31 ]. American McDonnell Douglas successfully developed a high-purity, high-density titanium alloy by using rapid solidification / powder metallurgy technology. Its strength at 760 ° C is equivalent to that of titanium alloy used at room temperature [26].

Titanium alloy titanium aluminum compound

Compared with general titanium alloys, the most important advantages of titanium-aluminum compounds are sodium-based Ti3Al (2) and TiAl () intermetallic compounds, which have good high-temperature performance (the highest operating temperatures are 816 and 982 ° C, respectively), strong oxidation resistance, and Good creep performance and light weight (density is only 1/2 of the nickel-based superalloy), these advantages make it the most competitive material for future aviation engines and aircraft structural parts [26].

Two Ti3Al-based titanium alloys, Ti-21Nb-14Al and Ti-24Al-14Nb- # v-0.5Mo, have begun mass production in the United States. Other developed Ti3Al-based titanium alloys include Ti-24Al-11Nb, Ti25Al-17Nb-1Mo, and Ti-25Al-10Nb-3V-1Mo, etc. [29]. The TiAl () -based titanium alloys are concerned with the composition range of Ti- (46-52) Al- (1-10) M (at.%), Where M is v, Cr, Mn, Nb, Mn, At least one of Mo and W. TiAl3-based titanium alloys have begun to attract attention, such as Ti-65Al-10Ni alloys [1].

Titanium alloy high strength and toughness type

-type titanium alloy was the first B120VCA alloy (Ti-13v-11Cr-3Al) developed by American Crucible company in the mid 1950s. -type titanium alloy has good hot and cold workability, is easy to forge, can be rolled and welded, and can obtain higher mechanical properties, good environmental resistance and good combination of strength and fracture toughness through solution-aging treatment. The most representative of the new high-strength and toughness -type titanium alloys are the following [26,30]:

Ti1023 (Ti-10v-2Fe- # al), this alloy is equivalent to the 30CrMnSiA high-strength structural steel commonly used in aircraft structural parts, and has excellent forging performance;

Ti153 (Ti-15V-3Cr-3Al-3Sn), the alloy has better cold workability than industrial pure titanium, and the room temperature tensile strength after aging can reach more than 1000MPa;

21S (Ti-15Mo-3Al-2.7Nb-0.2Si), this alloy is a new type of anti-oxidation, ultra-high-strength titanium alloy developed by Time Division of American Titanium Metals Company, which has good oxidation resistance, hot and cold workability Excellent, can be made into a foil with a thickness of 0.064mm;

Japanese steel pipe company (NKK) successfully developed SP-700 (Ti-4.5Al-3V-2Mo-2Fe) titanium alloy, which has high strength, superplastic elongation of up to 2000%, and superplastic forming temperature than Ti-6Al- 4V low 140 , can replace Ti-6Al-4V alloy with superplastic forming-diffusion connection (SPF / DB) technology to manufacture various aerospace components;

The BT-22 (TI-5v-5Mo-1Cr-5Al) developed by Russia has a tensile strength of more than 1105MPA.

Titanium alloy flame retardant titanium alloy

Conventional titanium alloys have a tendency to burn alkane under certain conditions, which greatly limits their applications. In response to this situation, various countries have launched research on flame retardant titanium alloys and made some breakthroughs. Alloy c (also known as Ti-1720) developed in the United States, with a nominal composition of 50Ti-35v-15Cr (mass fraction), is a flame-retardant titanium alloy that is not sensitive to continuous combustion and has been used in F119 engines. BTT-1 and BTT-3 are flame-resistant titanium alloys developed by Russia, both of which are Ti-Cu-Al series alloys. They have fairly good thermal deformation process properties and can be used to make complex parts [26].

Titanium alloy medical titanium alloy

Titanium is non-toxic, light, high-strength, and has excellent biocompatibility. It is a very ideal medical metal material, and can be used as an implant for human body. The Ti-6Al-4v ELI alloy is still widely used in the medical field. However, the latter will precipitate a very small amount of vanadium and aluminum ions, which reduces its cell adaptability and may cause harm to the human body. This problem has long caused widespread concern in the medical community. The United States began to develop aluminum-free, vanadium-free, and biocompatible titanium alloys for use in orthopedics as early as the mid-1980s. Japan, Britain, etc. have also done a lot of research work in this area and made some new progress. For example, Japan has developed a series of + titanium alloys with excellent biocompatibility, including Ti-15Zr-4Nb_4ta-0.2Pd, Ti-15Zr-4Nb-aTa-0.2Pd-0.20 ~ 0.05N, Ti-15Sn -4Nb-2Ta-0.2Pd and Ti-15Sn-4nb-2Ta-0.2Pd-0.20, these alloys have better corrosion strength, fatigue strength and corrosion resistance than Ti-6Al-4v ELI. Compared with + titanium alloy, titanium alloy has higher strength level, better incision performance and toughness, and is more suitable for implantation in human body. In the United States, 5 beta titanium alloys have been recommended to the medical field, namely TMZFTM (TI-12Mo- ^ Zr-2Fe), Ti-13Nb-13Zr, Timetal 21SRx (TI-15Mo-2.5Nb-0.2Si), Tiadyne 1610 (Ti-16Nb-9.5Hf) and Ti-15Mo. It is estimated that in the near future, this type of titanium alloy with high strength, low elastic modulus, and excellent formability and corrosion resistance is likely to replace the widely used Ti-6Al-4V ELI alloy in the medical field [28,32] ^[2] .