Titanium alloys densities

Figure 10.3 Photographs of the segregated state of binary granular mixtures of particles differing only in density after being shaken repeatedly until a steady segregation state is reached. The lighter particles are made of aluminum oxide (density p 1.31 g/cm ) and the heavier ones are made of (a) zirconium oxide (density p 2.87 g/cm ), (b) titanium alloy (density p 4.45 g/cm ), (c) cobalt-chromium-molybdenum alloy (density p 8.37 g/cm ), and (d) tungsten alloy (density p = 18.0 g/cm ), respectively. (Shi, Q. et al., Phys. Rev. E, 061302/1-4, 2007.)...

Peripheral pitting and etching associated with the low current densities arising outside the main machining zone occur when higher current densities of 45-75 A/cm are appHed. This is a recurrent difficulty when high alloy, particularly those containing about 6% molybdenum, titanium alloys are electrochemicaHy machined. 

In energy extraction, titanium alloys are being used in deep-water hydrocarbon and geothermal weUs for risers. Corrosion resistance, high strength, low modulus (flexible), and low density can result in risers one-fourth the weight and three times the flexibiHty of steel. 

Fig. 1.6. The titanium alloy implant for a replacement hip joint. The long shank is glued into the top of the femur. The spherical head engages in o high-density polythene socket which is glued into the pelvic socket.

Tantalum-Titanium Bishop examined the corrosion resistance of this alloy system in hydrochloric, sulphuric, phosphoric and oxalic acids and found that alloys containing up to about 50% titanium retained much of the superlative corrosion resistance of tantalum. Under more severe conditions, a titanium content of below 30% appears advisable from the standpoint of both corrosion resistance and hydrogen embrittlement, although contacting or alloying the material with noble metals greatly decreases the latter type of attack. Tantalum-titanium alloys cost less than tantalum because titanium is much cheaper than tantalum, and because the alloys are appreciably lower in density. These alloys are amenable to hot and cold work and appear to have sufficient ductility to allow fabrication. 

Titanium alloys comprise low- and high-strength materials with low density and high strength-weight ratio. The process industry uses a limited number of titanium alloys chiefly for their corrosion resistance. See Figure 4-14. 

Figure 4-14. Titanium alloys are used for low density, high strength-weight ratio and excellent corrosion resistance.

Pitting corrosion is usually associated with active-passive-type alloys and occurs under conditions specific to each alloy and environment. This mode of localized attack is of major commercial significance since it can severely limit performance in circumstances where, otherwise, the corrosion rates are extremely low. Susceptible alloys include the stainless steels and related alloys, a wide series of alloys extending from iron-base to nickel-base, aluminum, and aluminum-base alloys, titanium alloys, and others of commercial importance but more limited in use. In all of these alloys, the polarization curves in most media show a rather sharp transition from active dissolution to a state of passivity characterized by low current density and, hence, low corrosion rate. As emphasized in Chapter 5, environments that maintain the corrosion potential in the passive potential range generally exhibit extremely low... 

A comparison of thermophysical and thermomechanical properties for all three alloys is given in Table 7.12. Values for thermal conductivity, heat capacity, density, thermal diffusiv-ity, flow stress (800 °C, or 1470 °F, and strain rate =10 s ) and beta-transus temperature are given. Also recall that the CP titanium alloy has an hep crystal structure, the Ti-15-3 alloy has a bcc structure, and the Ti-6A1-4V alloy has a dual hcp/bcc structure. Furthermore, it is important to note that the total alloy content increases from CP titanium to Ti-6A1-4V to Ti-15-3. Study of the various properties suggests that ease of welding may be dependent on crystal structure, thermal conductivity, and beta-transus temperature. However, much more work is needed to understand differences in the FSW response of the three alloys. 

Wang J, van Apeldoom A, de Groot K (2006) Electrolytic deposition of calcium phosphate/ chitosan coating on titanium alloy growth kinetics and influence of current density, acetic acid, and chitosan. J Biomed Mater Res A 76(3) 503-511... 

R-phase, which serves as an intermediate phase to facilitate the transformation between martensite and austenite. Formation of the R-phase is reported to arise from the presence of dislocations and precipitates [11]. A substantial dislocation density is expected in the vwought nickel-titanium endodontic instruments and orthodontic wires, which are subjected to extensive mechanical deformation during manufacturing processes [12], Microstructural precipitates are a consequence of the inevitable deviation of the nickel-titanium alloy composition from the equi-atomic NiTi composition [13,14],... 

The trap theory is supported by experimental results for iron-titanium alloys in which the density of reversible and irreversible traps was varied [67]. Increasing the density of reversible traps, for example, was found to decrease the susceptibility to intergranular cracking, as described above. Reversible traps in the form of PdAl precipitates likewise appear to play an important role in suppressing intergranular cracking of a palladium-modified... 

Titanium alloys constitute the group of metallic materials showing the highest strength/weight ratio. The density is 4.5 g/cm. A grade widely used under corrosive conditions (the one with the best corrosion properties) is commercially pure titanium. 

---