Ti-6Al-4V

Ti-6Al-4V (UNS designation R56400), also sometimes called TC4, Ti64,[1] or ASTM Grade 5, is an alpha-beta titanium alloy with a high strength-to-weight ratio and excellent corrosion resistance. It is one of the most commonly used titanium alloys and is applied in a wide range of applications where low density and excellent corrosion resistance are necessary such as e.g. aerospace industry and biomechanical applications (implants and prostheses).

Studies of titanium alloys used in armors began in the 1950s at the Watertown Arsenal, which later became a part of the Army Research Laboratory.[2][3]

Increased use of titanium alloys as biomaterials is occurring due to their lower modulus, superior biocompatibility and enhanced corrosion resistance when compared to more conventional stainless steels and cobalt-based alloys.[4] These attractive properties were a driving force for the early introduction of a (cpTi) and a#b (Ti—6Al—4V) alloys as well as for the more recent development of new Ti-alloy compositions and orthopaedic metastable b titanium alloys. The latter possess enhanced biocompatibility, reduced elastic modulus, and superior strain-controlled and notch fatigue resistance.[5] However, the poor shear strength and wear resistance of titanium alloys have nevertheless limited their biomedical use. Although the wear resistance of b-Ti alloys has shown some improvement when compared to a#b alloys, the ultimate utility of orthopaedic titanium alloys as wear components will require a more complete fundamental understanding of the wear mechanisms involved.

Chemistry

(in wt. %)[6]

VAlFeOCNHYTiRemainder EachRemainder Total
Min3.55.5------------------
Max4.56.75.3.2.08.05.015.005Balance.1.3

Physical and Mechanical Properties
One possible microstructure of Ti-6Al-4V alloy with equiaxed alpha grains and discontinuous beta phase

Ti-6Al-4V titanium alloy commonly exists in alpha, with hcp crystal structure, (SG : P63/mmc) and beta, with bcc crystal structure, (SG : Im-3m) phases. While mechanical properties are a function of the heat treatment condition of the alloy and can vary based upon properties, typical property ranges for well-processed Ti-6Al-4V are shown below.[7][8][9] Aluminum stabilizes the alpha phase, while vanadium stabilizes the beta phase.[10][11]

Density, g/cm3Young's Modulus, GPaShear Modulus, GPaBulk Modulus,GPaPoisson's RatioYield Stress, MPa (Tensile)Ultimate Stress, MPa (Tensile)Hardness, Rockwell CUniform Elongation, %
Min4.4291044096.80.3188090036 (Typical)5
Max4.512113451530.37920950--18

Ti-6Al-4V has a very low thermal conductivity at room temperature, 6.7 - 7.5 W/m·K,[12][13] which contributes to its relatively poor machinability.[13]

The alloy is vulnerable to cold dwell fatigue.[14]

Heat Treatment of Ti-6Al-4V
Mill anneal, duplex anneal, and solution treatment and aging heat treatment processes for Ti-6Al-4V. Exact times and temperatures will vary by manufacturer.

Ti-6Al-4V is heat treated to vary the amounts of and microstructure of and phases in the alloy. The microstructure will vary significantly depending on the exact heat treatment and method of processing. Three common heat treatment processes are mill annealing, duplex annealing, and solution treating and aging.[15]

Applications
  • Implants and prostheses (wrought, cast or by Solid Freeform Fabrication (SFF))[16]
  • Additive Manufacturing[17]
  • Parts and prototypes for racing and aerospace industry. Used extensively within the Boeing 787 aircraft.
  • Marine applications
  • Chemical industry
  • Gas turbines
  • Firearm Silencers

Specifications
  • UNS: R56400
  • AMS Standard: 4911
  • ASTM Standard: F1472
  • ASTM Standard: B265 Grade 5[18]

References
  1. Paul K. Chu; XinPei Lu (15 July 2013). Low Temperature Plasma Technology: Methods and Applications. CRC Press. p. 455. ISBN 978-1-4665-0991-7.
  2. "Founding of ARL". www.arl. army.mil. Army Research Laboratory. Retrieved 6 June 2018.
  3. Gooch, William A. "The Design and Application of Titanium Alloys to U.S. Army Platforms -2010" (PDF). U.S. Army Research Laboratory. Retrieved 6 June 2018.
  4. Long, M.; Rack, H.J. (1998). "Titanium alloys in total joint replacement—a materials science perspective". Biomaterials. 18 (19): 1621–1639. doi:10.1016/S0142-9612(97)00146-4. PMID 9839998.
  5. Gutmanas, E.Y.; Gotman, I. (2004). "PIRAC Ti nitride coated Ti–6Al–4V head against UHMWPE acetabular cup–hip wear simulator study". Journal of Materials Science: Materials in Medicine. 15 (4): 327–330. doi:10.1023/B:JMSM.0000021096.77850.c5. PMID 15332594. S2CID 45437647.
  6. "ASTM Compass, Standard Specification for Wrought Ti-6Al-4V Alloy for Surgical Implant Applications. (UNS R56400)" (PDF). ASTM Compass.
  7. "Titanium Ti-6Al-4V (Grade 5), Annealed". asm.matweb.com. ASM Aerospace Specification Metals, Inc. Retrieved 14 March 2017.
  8. "Titanium Alloy Ti 6Al-4V Technical Data Sheet". cartech.com. Carpenter Technology Corporation. Retrieved 14 March 2017.
  9. "AZoM Become a Member Search... Search Menu Properties This article has property data, click to view Titanium Alloys - Ti6Al4V Grade 5". www.azom.com. AZO Materials. Retrieved 14 March 2017.
  10. Wanhill, Russell; Barter, Simon (2012), "Metallurgy and Microstructure", Fatigue of Beta Processed and Beta Heat-treated Titanium Alloys, Springer Netherlands, pp. 5–10, doi:10.1007/978-94-007-2524-9_2, ISBN 9789400725232
  11. Donachie, Matthew J. (2000). Titanium : a technical guide (2nd ed.). Materials Park, OH: ASM International. pp. 13–15. ISBN 9781615030620. OCLC 713840154.
  12. "ASM Material Data Sheet". asm.matweb.com. Retrieved 2020-06-20.
  13. Yang, Xiaoping; Liu, C. Richard (1999-01-01). "Machining Titanium and Its Alloys". Machining Science and Technology. 3 (1): 107–139. doi:10.1080/10940349908945686. ISSN 1091-0344.
  14. BEA (September 2020). "AF066 crash investigation results" (PDF).
  15. ASM Committee (2000). "The Metallurgy of Titanium". Titanium: A Technical Guide. ASM International. pp. 22–23.
  16. "Ti6Al4V Titanium Alloy" (PDF). Arcam.
  17. "Ti64 Titanium Alloy Powder". Tekna.
  18. "§1.1.5", ASTM B265-20a, Standard Specification for Titanium and Titanium Alloy Strip, Sheet, and Plate, West Conshohocken, PA: ASTM International, 2020, doi:10.1520/B0265-20A, retrieved 13 August 2020
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