History Of Titanium

Titanium is present on earth at 0.6% which makes it one of the most abundant element that we have.
Several names in the history are responsible for today’s importance of titanium and itsalloys in numerous disciplines. It took until 1791 to set the first suspicious on the existence of a new metal by William Gregor. Four years later, the German chemist Martin Heinrich Klaproth isolated titanium oxide from the mineral “rutile” and he named the element Titanium after the Titans from the Greek mythology. However, production of titanium in larger scales was initiated even in 1932 by Wilhelm Justin Kroll, who introduced a method for production of pure titanium by combining TiCl4 and magnesium. Even today this method is widely used and therefore Kroll

Figure 2 shows the unit cells of α and β-phase of titanium, together with some crystallographic parameters. In Figure 2. a) one of the three most densely packed (0002) planes are shown, also known as basal plane, one of the three {1010} planes, called prismatic planes and one of the six {1011} pyramidal planes for the HCP crystal structure of titanium. The axes a1, a2 and a3 are the close packed directions with indices . On the other hand, in Figure 2. b), is illustrated one of the six most densely packed {110} planes in the BCC crystal structure of titanium.
Alloys can show more complex structures, intermetallic compounds Ti3Al and shape memory alloys NiTi are the most common.

At room temperature titanium shows the hP2 structure, an hexagonal closed packed (hcp) structure type, with a packing density of 0.57 and transforms to a centred cubic (bcc) cI2 type at 1155K.
We can also see thanks to the phase diagram of Ti (Figure 1) that at pressures above 2GPa it transform into the hP3 structure and is expected to transform the bcc structure again at very high pressures.
Technical titanium alloys consist generally of α-Ti, β- Ti or a combination of the

Using properties of both phases titanium alloys can achieve outstanding properties combinations of a high specific strength, high ductility, high creep resistance and high fatigue strength as well as high corrosion resistance. The methods used can be summarized under the term of thermo-mechanical-processing and may include forging, hot- and cold-rolling as well as several thermal treatments.

1.1.5. Titanium alloys

Structural titanium alloys are often duplex alloys, containing the hcp α-phase and the bcc β-phase. In pure titanium the α-phase is stable below the allotropic transition temperatures Tβ =1155K while the β-phase is stable above Tβ, as shown in figure 1. Alloying elements stabilize one or the other phase over a vast range of temperatures, figure 4. A wide range of applications is served by using the allotropic α-and β-transformation and its local stabilization at various temperatures in order to realize different microstructures and micro compositions.

1.2. Alpha-Case in