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                  The common term “titanium” usually implies not only pure titanium, but also
                  its alloys. For the most part, industry consumes just alloys. Alloying titanium is
                  oriented to receiving grades with different properties and allows heat treatment                       TITANIUM GRADES
                  for some of them. Typical alloying elements for titanium are Aluminum,
                  Vanadium, Molybdenum, Ferrum, Chrome and others. Even small amounts
                  of these elements can drastically change the properties of the alloys.

                  Pure titanium can exist in two crystalline forms: the low-temperature α-phase with
                  hexagonal close-packed lattice and the higher-temperature β-phase with body-
                  centered cubic lattice. The alloying elements in titanium alloys lead to an increase
                  in α-phase or β-phase. Elements that strengthen, or stabilize a phase are called
                  stabilizers: α-stabilizers or β-stabilizers. For example, Aluminum, Nitrogen and
                  Plumbum are α-stabilizers, and Vanadium and Molybdenum are β-stabilizers. Some
                  elements added to titanium alloys do not strengthen either the α- or β-phase, but
                  are important as “neutral” elements that give certain properties to the alloy.

                  Based on its metallurgical characteristics, titanium is divided into the following groups:

                • Commercially pure titanium (unalloyed), featuring a good
                  corrosion resistance but low strength.
                • α-alloys (alpha-alloys), consisting of only α-phase and having a lot of
                  α-stabilizers, which feature strength retention at relatively high temperatures.
                • Near-α-alloys (near-alpha-alloys), which are α-alloys with a small addition of β-stabilizers
                  and have good resistance to creep for working temperatures 450°C -550°C.
                • α-β-alloys (alpha-beta-alloys), perhaps the most common group, which is a type
                  of mixture of both phases and contains α- and β-stabilizers. The alloys of this
                  group are suitable for heat treatment and aging for strength improvement.
                • β-alloys (beta-alloys) include a sufficiently large number of β-stabilizers to obtain
                  β-phase structure after treatment or even cooling in some cases. The group is
                  characterized by high hardenability and, therefore, high strength. However, increasing
                  the amount of the alloying elements leads to higher density. In addition, increasing
                  strength by solution treating and aging causes a reduction in ductility.

                  The family of near-β-alloys (near-beta-alloys) is sometimes separated from the
                  group because it does not retain a fully β-phase structure after treatment.

                  Generally, the α-alloys have better ductility and the β-alloys have higher strength.
                  The α-β-alloys lay between the mentioned two (Fig. 1).

                  There are different code systems for designating titanium. The American
                  Society for Testing and Materials (ASTM), for instance, uses a grade
                  numbering method: Grade 1, Grade 2, … , Grade 12,…

                  This guide utilizes the chemical composition system, where the designation shows the
                  percentage of main alloying elements in an alloy. For example: “Ti6Al4V” or
                  “Ti-6Al-4V” means that the titanium alloy contains 6% Aluminum (Al) and 4% Vanadium
                  (V). The amount of the other alloying elements is small and, if necessary, can be
                  found in detailed specification of the grade. The remaining component is titanium.

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