Alpha-beta titanium alloys

W. J. Evans. Optimising mechanical properties in alpha + beta titanium alloys. Mater Sci Eng A 243 %%, 1998. 

It is shown here that alpha, beta and alpha-beta titanium alloys can be friction stir welded. The phase transformations that occur in the nugget region and the heat affected zone are discussed. Residual stresses were found to be quite high in the present work. Tensile properties in transverse direction were... 

G.W. Kuhlmanef oZ., "Characterization of Ti-6-22-22S AHigh-Streng Alpha-Beta Titanium Alloy for Fracture Critical AppKcations, Proc. 7th Lot. Titanium Conf, San Diego, TMS/AIME, June 1992, to be published... 

Note Forgings were processed at 30 °C (50 °F) above the P transus temperature, 30 min, fan cooled+40 °C (70 °F) below the P transus, 1 h, AC + 540 °C (1000 °F), 8 h. Source G.W. Kuhlman et aL, "Charactmization ofTi-6-22-22S High-Strength Alpha-Beta Titanium Alloy for Fracture Critical Applications, Proc. 7th Int. Titanium Conf., San Diego, TMS/AIME, June 1992, to be published... 

DA Meyn, Effect of H3 irogen on Fracture and Inert-Environment Sustained Load Cracking Resistance of Alpha-Beta Titanium Alloys, Metall. Ty-ans., Vol 5, Nov 1974, p 2405... 

Industrial grades of pure titanium have relatively low tensile strength in comparison to alpha-beta stabilized alloys such as Ti6A14V. Therefore, the majority of industrial uses for titanium incorporate the alpha-beta alloys and as such these are the focus of most adhesion studies.As with other metals, there is a large range of pre-treatments available for titanium and its alloys, as indicated in Table 1. 

F 620, Specification for Alpha Plus Beta Titanium Alloy Forgings for Surgical Implants... 

Deformation Textures and Microstructures in Alpha- and Beta-Titanium Alloys... 

Developed for use in the aerospace industry, Ti-10-2-3 combines many of the advantages of the metastable beta titanium alloys without sacrificing certain inherent alpha-beta characteristics. It shows excellent hardenabihty in section sizes up to 125 mm (5 in.), but also demonstrates good short-... 

DUW] Duwez, P., Effeet of rate of cooling on the alpha-beta transformation in titanium and titanium molybdenum alloys, Trans. Metall. Soc. AIME, 191, (1951), 765-771. Cited on page 82. 

Many different titanium alloys have been developed for a large variety of applications. Titanium alloys are generally classified according to the equilibrium phases present in their microstructure at room temperature (Ref 1). They can be classified as commercially pure (CP) alloys and alpha alloys that mainly contain the hep phase, alpha-beta alloys that contain both phases, and metastable beta alloys and beta alloys that consist largely of the bcc phase. 

These alloys have an hep crystal structure known as alpha phase. The beta-transus temperature of CP titanium alloys is -910 15 °C (1670 27 °F), depending on the oxygen content (Ref 1). These alloys are not strengthened by heat treatment, like some other titanium alloys. They also have excellent corrosion resistance in seawater and marine environments. 

Milling summarizes the machining processes of square shoulder-, face-, profile-, and slotmUling. Titanium means titanium alloys (alpha and beta) used as a high strength, light weight, and corrosion resistant material f.e. in aerospace, medical, and automotive applications. 

Metallurgical classification. The crystallographic structure of titanium exhibits a phase transformation from a low-temperature close-packed hexagonal arrangement (i.e., a-hcp, alpha-titanium) to a high-temperature form body-centered cubic crystal lattice (i.e., 6-bcc, beta-titanium) at 882°C. This transformation can be considerably modified by the addition of alloying elements (Table 4.52) to produce at room temperature alloys that have all alpha, all beta, or alpha-beta structures. 

Therefore, the basic properties of titanium and its alloys strongly depend on their basic metallurgical structure and the way in which this is manipulated in their mechanical and thermal treatment during manufacture. Four main types of titanium alloy have been developed, and hence titanium alloys fall into the four categories alpha, near alpha, alpha plus beta, and beta. 

Alpha-titanium alloys. These alloys range in yield tensile strength from 173 to 483 MPa. Variations are generally achieved by alloy selection and not heat treatment. They usually contain alpha stabilizers and have the lowest strengths. However, they are formable and weldable. Some contain beta stabilizers to improve strength. Alpha-titanium alloys are generally in the annealed or stress-relieved condition. They are considered fully annealed after... 

Precautions in Use. Like most titanium alloys with alpha-beta microstructure, Ti-621/0.8 is susceptible to hydrogen embrittlement in hydrogenating solutions at room temperature, in air or reducing atmospheres at elevated temperatures, and even in pressurized hydrogen at cryogenic... 

Source R.E. Lewis et al., The Elevated Temperature Ductility Dip Phenomenon in Alpha, Near-Alpha, and Alpha-Beta Alloys, Titanium, Science and Technology, Vol 2, G. Lowering, U. Zwicker, and W. Bunk, Ed., Deutsche Gesellschaft fur Metallkunde, Gemnany, 1985, p 895-902... 

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