Chemical titanium alloys

Uses. The use of titanium alloys for cast partial dentures offers light weight, low cost, good ductihty, adequate stiffness, chemical passivity toward foods and oral fluids, and biocompatibiHty with the oral tissues. 

Researchers have tried to fabricate plates using many different metals— mainly, stainless steel, aluminum alloys, titanium alloys, nickel alloys, copper alloys, intermetallic alloys, and metal-based composites such as carbon fiber-reinforced aluminum alloys, carbon fiber reinforced copper alloys, etc. [26]. Although Ta, Hf, Nb, Zr, and Ti metals show good corrosion resistance and chemical stability [6], the cost of fhese metals is too high for them to be used as materials in metal plates. That is why relatively cheaper iron-based alloys, particularly stainless steel, have been popularly studied as plate material. In the following secfions, we will infroduce sfainless sfeel (SS) and SS plates, which have been extensively investigated and show promise for the final applications [6,11]. 

The most common SMAs are nickel-titanium alloys and copper alloys of various kinds. Nitinol, a specific alloy of nickel (Ni) and titanium (Ti), is probably the most widely used. (The word nitinol comes from the chemical symbols of its two metal components, along with an abbreviation for the Naval Ordnance Laboratory, where this alloy was discovered and studied in the early 1960s.) Although nickel and titanium alloys tend to be more expensive than copper materi-... 

The surface chemistry of Titanium alloys varies with each physical or chemical treatment. An example of ISS/SIMS results from a typical chemical pretreatment for T1-6A1-4V Is seen in Figure 1. Here the sample was degreased, etched in HN0-/HF and converted with a mixture of HF, NaF and Na PO In aqueous solution. Spectra from... 

As a result of treatment of experimental extraction curves, the range of activation energies of the traps for aluminum and aluminum alloys was determined. This range stretches from 0.2 eV to 0.8 eV. Consequently, one can suppose that there is no chemically bound hydrogen in the alloys. For the titanium alloys, the maximum activation energy equals 1.5 eV. 

Most modern industrial materials are designed to be passive i.e., covered by an adherent, chemically inert, and pore-free oxide that is highly insoluble in aqueous solutions and hence dissolves at an extremely slow rate. Examples would be modern stainless steels, nickel-chromium-molybdenum, and titanium alloys. The concept of passivity is often defined by reference to the polarization curve for metals and alloys in aggressive acidic solutions, Fig. 22. This curve defines the potential regions within which the alloy would be expected to corrode actively or passively. 

For some materials (e.g., nickel alloys), the current is a direct measure of the rate of crevice propagation. For systems such as titanium alloys, however, internal cathodic reactions are also possible, as is illustrated in Fig. 29. This figure shows schematically the important electrochemical and chemical reactions occurring within the creviced area and on the coupled counterelectrode. This system will be used to illustrate the information that can be obtained from this galvanic coupling technique and how it can then be used directly in the development of models. 

In recent years, several designs of rotor made from carbon-fibre reinforced plastic have come on to the market, combining strength, lightness and some resistance to chemical corrosion. Most rotors, however, are made of aluminium or titanium alloy. 

The ingots of alloys under study were made on the commercial titanium alloy BT1-0 base using arc and electron beam melting. The BT1-0 alloy contains admixtures as follows Si < 0.1 Fe < 0.25 C < 0.07 N < 0.04 O < 0.2 others <0.3 wt.% according to the FSU standard. Chemical compositions of the studied alloys are given in Table 1. 

The technology of MEM of multicomponent titanium alloys has been developed which can produce ingots with a high chemical and structural homogeneity and precise preset chemical composition. 

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