In Focus

Third and final episode on our in-depth study on Titanium: let’s find out more about the last alloy types!

After introducing the general characteristics of titanium alloys in the first episode and the description of the first alloys in the second, we now continue with the discovery of the last existing types.

The α + β alloys

By adding appropriate combinations of α and β-stabilising elements, it is possible to obtain the microstructure of this group of titanium alloys, which feature the simultaneous presence of the α and β phases at room temperature.

They are undoubtedly the best known and most widely used titanium alloys and among them the Ti-6Al-4V (or grade 5) alloy is certainly worth a mention, which alone represents about 50% of titanium production across the globe.

In fact, this material boasts an outstanding combination of mechanical strength, ductility, fatigue and corrosion resistance, although it is not recommended to use it at temperatures above 300°C.

The version with low content of interstitial elements, Ti-6Al-4V ELI (or grade 23), is characterised by exceptionally high fracture resistance values and is also suitable for applications at cryogenic temperatures.

As in the case of CP titanium, there are versions with Pd (grade 24) and Ru (grade 29) additives to increase the resistance to crack corrosion also in deaerated acid environments.

To mention an example of a significant application, we can take the fan used by the Trent 800 turbofan aircraft engine, produced by the British company Rolls-Royce plc, which was made using twenty-six Ti-6Al-4V alloy blades. 

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