TA21 titanium alloy is a nearly α-type titanium alloy with high comprehensive properties and good welding performance. It is mainly used in aircraft engine oil leakage and ventilation systems, gas exhaust system ducts, and control system pipes.
The chemical composition of TA21 titanium alloy is expressed as T-1Al-1Mn, and the contents of aluminum (Al) and manganese (Mn) are less than 1.5%. Due to the presence of β phase in the alloy, the plasticity in hot and cold states is close to α+β type alloy. Therefore, TA21 titanium alloy has excellent hot working properties and can be processed by hot working methods such as forging, extrusion, and rolling. At the same time, it also has good cold working properties, and thin plates and pipes can be cold processed.
Compared with other titanium alloys, TA21 titanium alloy has better welding performance and does not require heat treatment of the welded joint to stabilize its structure. This makes it widely used in the aviation field.
Generally speaking, TA21 titanium alloy is a near-α titanium alloy with high comprehensive performance and good welding performance, and plays an important role in aeroengines and aviation systems.
What is Ti-Al-Mn titanium alloy?
Ti-Al-Mn titanium alloy refers to titanium alloy containing elements such as titanium (Ti), aluminum (Al) and manganese (Mn). This alloy was successfully developed in the former Soviet Union in the late 1950s and belongs to the nearly α-type titanium alloy family. There are several representative alloy grades, such as OT4-0, OT4-1, OT4, BT4 and OT4-2, etc. The alloy contains approximately the same amount of manganese (about 1-2%) and different amounts of aluminum (about 1-7%). Different aluminum contents can produce alloys with different strength levels and thermal strengths.
Ti-Al-Mn titanium alloy has medium strength and thermal strength, and its phase composition consists of α phase and a small amount of β phase (about 2-8% β phase content). This alloy retains many of the advantages of α-type titanium alloys and α+β-type titanium alloys, and has good plasticity in sheet metal stamping processes and various good welding properties. The alloy also shows good thermal stability under long-term high-temperature operating conditions, such as stress-containing heating.
Aluminum is an alloy element that stabilizes the α phase. It is soluble in the β phase and the α phase, and has a high solubility in the α phase. It is the main element for solid solution strengthening of nearly α-type titanium alloys. Adding aluminum increases the alloy’s strength and heat resistance while reducing its weight. Generally, the aluminum content in the alloy does not exceed 6%. When the aluminum content exceeds 7%, that is, the electron concentration of the alloy is greater than 2.12, the Ti3Al phase begins to precipitate. The Ti3Al phase is an ordered version of the disordered α phase. It is brittle and will reduce the overall properties of the alloy, especially the plasticity.
Manganese is a beta eutectic element with higher solubility and faster diffusion rate in the beta phase, but lower solubility in the alpha phase. Within the α-phase solid solubility range, manganese has a very obvious strengthening effect on titanium alloys and can significantly increase the strength of the alloy, but it will reduce high-temperature creep resistance. Due to the thermal instability of high content of manganese under certain conditions, it will cause eutectoid decomposition of β solid solution and precipitation of compounds. Therefore, in practical applications, only alloys with relatively low manganese content have been widely used. It is worth noting that the vapor pressure of manganese is relatively high, requiring the alloy to be smelted under neutral gas instead of vacuum smelting to ensure the manganese content in the alloy.
To sum up, the Ti-Al-Mn titanium alloy is a nearly α-type titanium alloy with medium strength and thermal strength. By adjusting the content of aluminum and manganese, alloys with different performance levels can be obtained. It is widely used in industrial production and testing
Chemical composition of TA21 titanium alloy (%)
Physical properties of TA21 titanium alloy
Elastic modulus: 115GPa
Shear modulus: 44.1GPa
Application of TA21 titanium alloy
This alloy has similar processing characteristics to pure titanium. It not only has good process plasticity, welding performance and thermal stability, but also has higher strength, durability and creep resistance than pure titanium because it contains 1% Al and Mn. It can be used to manufacture products such as plates, strips, foils, pipes, bars, profiles and forgings. It can manufacture various structural parts through welding, stamping, bending and other methods, and can work at 300℃ for a long time. This alloy has been listed in rOCT and OCT standards in the former Soviet Union, is industrially produced, and is used in aviation and other industrial sectors. TA21 titanium alloy pipes are used as oil leakage and ventilation systems, gas exhaust system ducts and control system pipes for aircraft engines with operating temperatures below 250°C.