Hydrogen embrittlement titanium alloys

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. 

The method is more useful with titanium, and the effect of alloying titanium with a small amount of palladium is described in Section 5.4. The use of platinum in the prevention of hydrogen embrittlement in tantalum. 

Table 10.9 lists some common zinc anode alloys. In three cases aluminium is added to improve the uniformity of dissolution and thereby reduce the risk of mechanical detachment of undissolved anode material . Cadmium is added to encourage the formation of a soft corrosion product that readily crumbles and falls away so that it cannot accumulate to hinder dissolution. The Military Specification material was developed to avoid the alloy passivating as a result of the presence of iron . It later became apparent that this material suffered intergranular decohesion at elevated temperatures (>50°C) with the result that the material failed by fragmentation". The material specified by Det Norske Veritas was developed to overcome the problem the aluminium level was reduced under the mistaken impression that it produced the problem. It has since been shown that decohesion is due to a hydrogen embrittlement mechanism and that it can be overcome by the addition of small concentrations of titanium". It is not clear whether... 

R.E. Buxbaum, R. Subramanian, J.H. Park, and D L. Smith, Hydrogen Transport and Embrittlement for Palladium Coated Vanadium-Chromium-Titanium Alloys, Journal of Nuclear Material, Part A, 233-237, 1996, pp.510-512. 

Buxbaum, R. E, Subramanian, R, Park, J. H, Smith, D. L. Hydrogen transport and embrittlement for palladium coated vanadium-chromium-titanium alloys. J Nucl Mater. 1996 233-237 510-2. 

The reactivity of the titanium alloys as well as the refractory metals tools is another concern. Elimination of atmospheric contamination is required to limit pickup of nitrogen, oxygen, and hydrogen from the atmosphere by both workpiece and tools in order to avoid embrittlement. Hence, the use of inert gas shielding is required during FSW of titanium alloys. Use of an inert gas chamber that can be backfilled with inert gas prior to each weld is preferred. 

After test exposure, sample evaluation for hydrogen may include tensile, notched tensile, bend, ductility (for example, drawn cup), and/or impact Charpy tests, hydrogen analysis, or cross-sectional microstructural examination, or a combination thereof. Uniaxial, smooth-specimen tension testing is generally of litde value in diagnosing the subde embrittling effects of hydrogen. Titanium alloys tend to... 

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