What is Titanium Alloy

Titanium alloy refers to a variety of alloy metals made of titanium and other metals.

Titanium is an important structural metal developed in the 1950s, Titanium and titanium alloys have comprehensive advantages such as low density, high specific strength, high temperature resistance, low temperature resistance, corrosion resistance, weldability, non-magnetic, and good biocompatibility. It is the material with the highest strength, the best heat resistance and the best corrosion resistance among the three major light metals (Al, Mg, Ti). It is widely used in aviation, aerospace, ships, weapons, chemicals and other fields.

Classification of titanium alloy

Titanium is an allotrope with a melting point of 1720°C and a close-packed hexagonal lattice structure when it is lower than 882°C, called α-titanium; Above 882°C, it has a body-centered cubic lattice structure, which is called β titanium. Utilizing the different characteristics of the above two structures of titanium, adding appropriate alloying elements to gradually change the phase transition temperature and phase content to obtain titanium alloys with different structures.

α titanium alloy

The structure of α-titanium alloy is a single-phase α solid solution. The α-phase stabilizing element Al and the neutral elements Sn and Zr are mainly added to strengthen the α-phase by solid solution. The main advantages of α-titanium alloy are good welding performance, stable structure and high corrosion resistance; the disadvantages are low strength, poor thermal processing performance, and cannot be strengthened by heat treatment.

β titanium alloy

The structure of β-titanium alloy is a single-phase β solid solution, and its main alloying elements are β-stable elements such as Cr, Mo, Mn, Fe, and V. The crystal structure of β-titanium alloy at room temperature and high temperature is body-centered cubic, has good plasticity, and has good cold forming performance in the quenched state. β titanium alloy can be strengthened by heat treatment. After aging strengthening, it has both high yield strength and fracture toughness, and high hardenability. It can make large-sized parts obtain uniform high strength after heat treatment. But the disadvantage is high density and low elastic modulus.

α+β titanium alloy

α+β titanium alloy is a dual-phase alloy, which has good comprehensive properties, good structural stability, good toughness, plasticity and high-temperature deformation properties, and can be well processed by hot pressure, and can be quenched and aged to strengthen the alloy. The strength after heat treatment is about 50% to 100% higher than that of the annealed state; the strength is high at high temperature, and it can work at a temperature of 400°C to 500°C for a long time, and its thermal stability is inferior to that of α-titanium alloy.

Among the three titanium alloys, α titanium alloy and α+β titanium alloy are the most commonly used; α titanium alloy has the best machinability, followed by α+β titanium alloy, and β titanium alloy is the worst. The code name of α titanium alloy is TA, the code name of β titanium alloy is TB, and the code name of α+β titanium alloy is TC (GB/T3620.1-2016 titanium and titanium alloy grade and chemical composition).

Application of XRD in Titanium Alloy Detection

X-ray diffraction (XRD) is an indispensable tool in the field of materials research. Whether it is analyzing the crystal structure of unknown substances or identifying the phases of multi-phase mixtures, XRD has played an indispensable role.

Titanium alloys can obtain different phase compositions and structures through treatment processes to achieve different performance characteristics. X-ray diffractometer can be used to obtain the phase composition and content ratio of titanium alloy, and provide favorable data support for technical routes such as titanium alloy synthesis technology and processing technology.

Test Case

Phase analysis of BS-T-5A sample using FRINGE desktop X-ray diffractometer

American standard BS-T-5A chemical composition

National standard TC-4 (Ti-6Al-4V) chemical composition

Phase identification

The installation display picture of titanium alloy BS-T-5A before testing on FRINGE

Phase quantitative results of titanium alloy BS-T-5A displayed by CrystalX software

Analysis and Conclusion

From the chemical composition table of BS-T-5A titanium alloy, it can be clearly known that it contains 6.33% Al and 4.1% V. The chemical composition is similar to that of the national standard TC-4 (Ti-6Al-4V). From the naming rules of titanium alloy grades (GB/T3620.1-2016 titanium and titanium alloy grades and chemical composition), it is an α+β titanium alloy. Among them, the structure of the α-titanium alloy is a single-phase α solid solution with a close-packed hexagonal structure, and the α-phase stabilizing element Al is added. The structure of β-titanium alloy is a body-centered cubic single-phase β solid solution, and the β-phase stabilizing element V is added. 

In addition, from the FRINGE test analysis of LANScientific benchtop ray diffractometer: BS-T-5A titanium alloy is composed of 58.83% α-Ti and 41.17% β-Ti, This is highly consistent with the element ratio relationship of 6.33% Al and 4.1% V contained in BS-T-5A titanium alloy.