T.O. 1-1A-9SECTION VTITANIUM AND TITANIUM ALLOYS.5-1. CLASSIFICATION.5-2.Titanium is produced in pure form as well as in various alloys. Pure titanium is commonly known as unalloyed. Itcan be cast, formed, joined, and machined with relative ease as compared to the various alloy grades. Unalloyedtitanium cannot be he; t treated. Therefore, its uses are limited to end items not requiring the higher strengths obtainedfrom the heat treatable alloys.5-3.Titanium is a very active metal, and readily dissolves carbon, oxygen, and nitrogen. The most pronounced effectsare obtained from oxygen and nitrogen. For this reason, any heating process must be performed in a closely controlledatmosphere to prevent the absorption of oxygen and nitrogen to a point of brittleness.5-4.GENERAL5-5.MILITARY AND COMMERCIAL DESIGNATIONS . There are presently two military specifications in existence(See Table 5-1) covering alloyed and unalloyed titanium in classes established to designate various chemicalcompositions. For the selection of the proper class and form of stock required for a particular purpose, reference will bemade to Table 5-1.5-6.PHYSICAL PROPERTIES. Limited physical properties are available on the titanium compositions covered byexisting military specifications. Compared to other materials, the melting point of titanium is higher than that of any ofthe other construction materials currently in use. The density of titanium is intermediate to aluminum and steel.Electrical resistivities of titanium are similar to those of corrosion resistant steel. The modulus of elasticity is somewhatmore than half that of the alloy steels and the coefficient of expansion is less than half that of austenitic stainless steels.5-7.MECHANICAL PROPERTIES . As previously pointed out, titanium is a very active metal and readily dissolvescarbon, oxygen and nitrogen. All three elements tend to harden the metal; oxygen and nitrogen having the mostpronounced effect.5-8.The control of these elements causes considerable difficulty in obtaining correct mechanical properties during thefabrication of titanium. This variation in mechanical properties is the cause of difficulties encountered in the fabricationof parts, since the absorption of small amounts of oxygen or nitrogen makes vast changes in the characteristics of thismetal during welding, heat treatment, or any application of heat in excess of 800°F.5-9.Operations involving titanium requiring the application of heat in excess of 800°F must be performed in a closelycontrolled atmosphere by methods explained in future paragraphs. The nominal mechanical properties are listed inTable 5-2.5-10. METHODS OF IDENTIFICATION . Methods of distinguishing titanium alloys from other metals are simple anddefinite. One quick method is to contact the titanium with a grinding wheel. This results in a pure white trace ending in abrilliant white burst.Also, identification can be accomplished by moistening the titanium and marking the surface with a piece of glass. Thisleaves a dark line similar in appearance to a pencil mark. Titanium is non-magnetic. To positively identify the variousalloys, a chemical or spectrographic analysis is necessary.5-11. HARDNESS TESTING. Hardness is the resistance of a metal to plastic deformation by penetration, indentation, orscratching, and is usually a good indication of strength. This property can be measured accurately by the Brinell,Rockwell or Vickers Technique. The hardness to be expected from the various alloys and unalloyed titanium is listed inTable 5-2.5-12. TENSILE TESTING . The useful strength of a metal is the maximum load which can be applied without permanentdeformation. This factor is commonly called yield strength. The tensile strength of a metal is that load, in pounds persquare inch, at which complete failure occurs. In the case of titanium the yield strength is the most important factor andis therefore used by industry to designate the various types of unalloyed titanium.5-13. NON-DESTRUCTIVE TESTING . Titanium and titanium alloys are highly susceptible to stress risers resulting fromscratching, nicking, and notching. For this reason, close visual inspection is required of all raw stock prior to any formingor machining operations. All scratches, nicks and notches must be removed, before fabrication, by sanding andpolishing.5-14. and 5-15. Deleted.Change 45-1
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