Classification of Titanium and Titanium Alloys

Titanium and titanium alloys can be classified in various ways, with their final properties largely depending on the alloying elements added and subsequent processing techniques. Below is a summary of the main classification methods, performance characteristics, and comparisons between different types to help you quickly understand.

Classification and Performance Overview of Titanium and Titanium Alloys

According to the organizational structure (i.e., the matrix phase at room temperature), this is the most fundamental and widely used classification method for titanium alloys, which can directly reflect the basic properties of the material.

1. Industrial pure titanium

· Main Characteristics: Essentially belongs to α-type titanium alloy.

· Grade: TA1, TA2, TA3, TA4 (The higher the number, the greater the impurity content, higher strength, but reduced plasticity).

Core Performance and Applications: Excellent plasticity, toughness, and weldability, with outstanding corrosion resistance. Cannot be strengthened by heat treatment. Primarily used in high-corrosion-resistant fields such as chemical and marine engineering.

2. α-titanium alloy and near-α titanium alloy

· Key characteristics: The room temperature microstructure consists entirely of the α phase or contains a small amount of the β phase. Elements such as aluminum (Al) and tin (Sn), which stabilize the α phase, are typically added to the alloy.

· Grade: TA series (e.g., TA7).

· Core Performance and Applications: Excellent heat resistance, creep resistance, and oxidation resistance, with stable microstructure and good weldability. However, it cannot be strengthened by heat treatment and has low room-temperature strength. Suitable for aerospace engines and heat-resistant components operating at 500-600°C for extended periods.

3. (α+β) titanium alloy

· Key Features: The room temperature microstructure consists of coexisting α and β phases. The alloy contains both α-stabilizing elements (e.g., Al) and β-stabilizing elements (e.g., V, Mo).

Grade: TC series (e.g., the most classic TC4, Ti-6Al-4V).

· Core Performance and Applications: Excellent comprehensive performance, balancing strength and plasticity, with heat treatment strengthening capability and superior process plasticity. Post-heat treatment strength can be increased by 50%-100% compared to the annealed state. It is the most widely used material, serving as a primary choice in aerospace structural components, biomedical applications (such as artificial joints), and other fields.

4. Beta titanium alloy and near-beta titanium alloy

· Main characteristics: After annealing or quenching, the microstructure consists entirely of the metastable β phase, requiring "aging" treatment to precipitate the secondary α phase for strengthening. It contains a high amount of β-stabilizing elements such as molybdenum (Mo) and vanadium (V).

· Model: TB series.

· Core Performance and Applications: It exhibits the highest room-temperature strength, good plasticity in the quenched state, and is easy to cold form. However, it has poor thermal stability and is unsuitable for high-temperature use. It is commonly used for high-strength fasteners, springs, and products requiring good cold formability, such as eyeglass frames and golf clubs.

The comprehensive performance characteristics of titanium and titanium alloys, in addition to the characteristic differences brought by the above classification, titanium materials as a whole have some common and significant advantages and disadvantages:

Highlight advantages

1. High specific strength: The density is only about 60% of steel, but the strength is equivalent to it, so it has a very high specific strength (strength/density ratio) and is an ideal material for weight reduction and efficiency improvement in aerospace.

2. Excellent corrosion resistance: In humid atmospheres, seawater, and most acidic, alkaline, and chloride media, its corrosion resistance is far superior to stainless steel. Pure titanium is widely used in the chemical industry.

3. Good high and low temperature performance: Some titanium alloys can work for a long time at 400-600 ℃; Some special grades (such as TA7) can still maintain good plasticity at ultra-low temperatures of -253 ℃.

4. Good biocompatibility: non-toxic, non-magnetic, with an elastic modulus similar to that of human bones, it is an ideal material for human implants (such as artificial joints and dental implants).

Main drawbacks and limitations

1. High cost: The process from ore smelting to processing into materials is complex, with high energy consumption, resulting in expensive prices.

2. Poor processing performance: low thermal conductivity, rapid heat accumulation during cutting; The elastic modulus is small, prone to deformation, and has a large rebound, making machining difficult and tool wear fast.

3. High chemical activity: It is prone to react with gases such as oxygen, nitrogen, and hydrogen at high temperatures (>600 ℃), forming a hard and brittle surface layer, which requires melting and heat treatment under vacuum or inert gas protection.

How to choose the appropriate titanium material?

If you have specific usage scenarios, you can make a preliminary judgment based on the above information:

·Pursuing the best corrosion resistance: Priority is given to industrial pure titanium (TA series).

·Need to work at high temperatures (such as engine components): Alpha or near alpha titanium alloys (TA series) should be selected.

·Pursuing high comprehensive performance (balance of strength, plasticity, and processability): The most commonly used is (α+β) titanium alloy, especially TC4 (Ti-6Al-4V).

·Requirement for ultra-high strength or excellent cold formability: beta or near beta titanium alloys (TB series) can be explored.

·For human implantation: Special titanium alloys with excellent biocompatibility, such as Ti-6Al-4V ELI (ultra-low gap element) or Ti-6Al-7Nb, should be selected.

I hope this information can help you establish a systematic understanding of titanium materials. If you can provide specific application areas (such as aerospace, chemical, medical implants, or sports equipment), I can offer you more targeted analysis and material selection recommendations.