Titanium deformation temperatures

Thus, in the future all great experience of processing iron-based alloys could be employed to produce the alloys on the basis of titanium. The preliminary data show that a level of properties, which could be realized with titanium "steels appears to be attractive enough. Some properties of the deformed alloys of system Ti-Si-Al-Zr are listed in the Table 1. It is obvious also some distinction in properties of titanium steels depending on deformation temperature. Namely, alloys deformed in a phase field, have higher plasticity conversely, alloys deformed in 3 phase field, possess higher heat resistance. 

Table lc.8 Deformation temperatures for various titanium materials (Ref. 1.13)... 

O.N. Senkov, I.O. Bashkin, S.S. Khasanov, and E.G. Ponyatovsky, Grain structure of titanium alloy VT20 after hydrogen treatment and deformation at moderate temperatures, Fiz. Met. Metallovedeniye, 76 128 (1993). 

Shape-memory alloys (e.g. Cu-Zn-Al, Fe-Ni-Al, Ti-Ni alloys) are already in use in biomedical applications such as cardiovascular stents, guidewires and orthodontic wires. The shape-memory effect of these materials is based on a martensitic phase transformation. Shape memory alloys, such as nickel-titanium, are used to provide increased protection against sources of (extreme) heat. A shape-memory alloy possesses different properties below and above the temperature at which it is activated. Below this temperature, the shape of the alloy is easily deformed due to its flexible structure. At the activation temperature, the alloy can be changed by applying a force, but the structure resists this deformation and returns back to its initial shape. The activation temperature is a function of the ratio of nickel to titanium in the alloy. In contrast with Ni-Ti, copper-zinc alloys are capable of a two-way activation, and therefore a reversible variation of the shape is possible, which is a necessary condition for protection purposes in textiles used to resist changeable weather conditions. 

The objectives of this Workshop, to present and discuss new results in the development and processing of metallic materials with high structural efficiency and to establish new interactions and networks between the participants, were successfully met. A number of new developments were presented and discussed at this Workshop, including recent information on titanium alloys modified with relatively small amounts of B and Si to provide dramatic improvements in strength and stiffness, and new A1 alloys strengthened with quasicrystalline precipitates for good elevated temperature properties. In addition, a current extensive update on severe plastic deformation and on nanocrystalline metals for structural applications was provided. 

Recently, the integration of actuators into structures has also been researched. Shape Memory Alloys (SMA)-based actuators can be embedded into composites in the form of large diameter, plastically deformed wires. SMA are nickel/titanium alloys with a surprising property if plastically deformed at a low temperature (in a martensitic phase), they can recover the original shape and dimensions though heating above a definite temperature. When SMA are embedded and then heated, the restraints on free deformation imposed by the host composite originate a distributed stress which deforms the structure or modifies its vibrational response. 

One interesting alloy of titanium and nickel, called Nitinol, exhibits shape-memory properties. Below a particular temperature (the transformation temperature), the crystal structure of the alloy is such that it can be plastically deformed (martensitic). As the alloy is heated, the crystal structure alters to one that is more ordered and rigid (austenitic), and the deformed metal reverts to its original shape. This effect has been exploited in a number of devices, including a stent (a device used to hold open passageways such as arteries). The stent is placed inside a small-diameter catheter for insertion into the body, where it expands on being warmed to bod y temperature. 

Answer by author This behavior is common with metals of high purity. In the case of titanium, recent investigations indicate that the operative modes of deformation are dependent upon purity level in addition to temperature. Similar results were also obtained by R. W. Guard of the General Electric Research Laboratory in his Report No. 55-RL-1339, July, 1955. 

When the material is in its martensite form, it is soft and ductile and can be easily deformed like tin pewter. Superelastic NiTiNOL is highly elastic, while austenitic NiTiNOL is quite strong and hard, similar in that way to titanium metal. The NiTi material has all these properties, their specific expression depending on the temperature at which it is used. 

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