Test methods titanium alloys

It follows from these data that addition of silicon in the basic titanium alloy rises its resistance to oxidation. Especially it becomes apparent at silicon content of 2 wt. % and more. Further its increase does not change heat-resistance practically. Data of tests obtained by different methods for 5 hours exposure coincide practically. The results of short-time tests are confirmed at the increase of exposure time to 30 hours the best characteristics have alloy with 2 wt. % Si as well as that with additional aluminium alloying. If at the short-time tests insignificant dependence is revealed at increasing silicon content up to 6 wt. % and addition of 3 wt. % Al, this is not revealed at the long-term exposure when resistance to... 

Table 9.1 summarizes environmental alloy combinations that have been shown to produce see. The test temperature accelerates the See for most of the systems listed in Table 9.1. Electrochemical methods and stress corrosion tests should be performed to evaluate possible corrosion environments for a given alloy. More information on these and additional systems may be found in the ASM Metals Handbook [30]. Other significant alloys include nickel alloys [31], austenitic stainless steel [30], carbon steels [32], copper alloys [33], ferritic, martensitic, duplex [31,32], titanium alloys [33], and aluminum alloys [34].

F 2004, Test Method for Transformation Temperature of Nickel-Titanium Alloys by Thermal Analysis... 

F 2082, Test Method for Determination of Transformation Temperature of Nickel-Titanium Shape Memory Alloys by Bend and Free Recovery... 

It is important to know where titanium might exhibit susceptibility to corrosion attack in order to establish which corrosion test methods may be applicable or relevant to titanium alloys. Table 2 presents a list of specific environments where some form of corrosion susceptibility has been observed on titanium alloys in laboratory tests or service experience. The table indicates the relevant mode of corrosion degradation that can be expected, general scope of titanium alloys susceptible, and comments on critical factors that strongly influence each corrosion phenomenon. 

Immersion testing wiU generate weight loss data, or corrosion current measurements can be obtained from stan-deird electrochemical polarization tests (see ASTM G 5, Standard Reference Test Method for Making Potentiostatic and Potentiodynamic Anodic Polarization Measurements see also Ref 27). Corrosion rates in millimeters per year (mpy) for titanium alloys can be calculated from sample weight loss data as follows ... 

Test methods for assessing the SCC resistance of titanium alloys can be grouped into three basic categories ... 

In the methods used for the investigation of corrosion resistance, biocompatibility and bioadhesion the researchers try to simulate and imitate the natural in vivo condition of the implant. Only in the near past have efforts been made to standardize these tests. Because of a longtime decline of standardization the tests described up until now in literature differ and the results of such diversified tests are not comparable. Corrosion measurements, for example, are performed in different solutions with changing pH values and atmospheres (aerated or de-aerated). Only if different materials have been investigated in one test and under the same conditions does a comparison of their behaviour for this test seem possible. Nevertheless, regarding the differing test results, the most corrosion resistant materials seem to be the special metals (titanium, niobium, tantalum and their alloys), followed by wrought CoCr-based, cast CoCr-based alloys and stainless steel. 

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