Ti-6Al-4V Explained

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 specific strength 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]}

A 1948 graduate of MIT, Stanley Abkowitz (1927-2017) was a pioneer in the titanium industry and is credited for the invention of the Ti-6Al-4V during his time at the US Army’s Watertown Arsenal Laboratory in the early 1950s.^[4]

Titanium/Aluminum/Vanadium alloy was hailed as a major breakthrough with strategic military significance. It is the most commercially successful titanium alloy and is still in use today, having shaped numerous industrial and commercial applications.^[5]

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.^[6] These attractive properties were a driving force for the early introduction of α (cpTi) and α+β (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.^[7] 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. %)^[8]

	V	Al	Fe	O	C	N	H	Y	Ti	Remainder Each	Remainder Total
Min	3.5	5.5	--	--	--	--	--	--	--	--	--
Max	4.5	6.75	.3	.2	.08	.05	.015	.005	Balance	.1	.3

Physical and mechanical properties

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.^{[9] [10] [11]} Aluminum stabilizes the alpha phase, while vanadium stabilizes the beta phase.^[12]

	Density	Young's Modulus	Shear Modulus	Bulk Modulus	Poisson's Ratio	Tensile Yield Stress	Tensile Ultimate Stress	Hardness	Uniform Elongation
Min					0.31			36 Rockwell C (Typical)	5%
Max					0.37			--	18%

Ti-6Al-4V has a very low thermal conductivity at room temperature of 6.7 to 7.5 W/m·K,^{[13] [14]} which contributes to its relatively poor machinability.

The alloy is vulnerable to cold dwell fatigue.^{[15] [16]}

Heat treatment of Ti-6Al-4V

Ti-6Al-4V is heat treated to vary the amounts of and microstructure of

\alpha and \beta 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.^[17]

Applications

• Aerospace structures. The Boeing 787 is 15% titanium by weight,^[18] and the Airbus A350 is 14%.^[19]
• Biomedical implants and prostheses^[20]
• High-performance race cars
• High-end bicycles
• Additive manufacturing^[21]
• Apple iPhone 15 Pro (Max) case
• Marine applications: Ti-6Al-4V Grade 5 is extensively used in marine applications due to its exceptional corrosion resistance in seawater environments.^[22] Ti-6Al-4V is applied in components exposed to marine atmospheres and underwater conditions, such as shipbuilding, offshore oil and gas platforms, and subsea equipment.^{[23] [24]} Its resistance to corrosion helps in reducing maintenance costs and extending the lifespan of marine equipment. ^[25]

Specifications

• UNS: R56400
• AMS Standard: 4928
• ASTM Standard: F1472
• ASTM Standard: B265 Grade 5

Notes and References

1. Book: Paul K. Chu. XinPei Lu. Low Temperature Plasma Technology: Methods and Applications. 15 July 2013. CRC Press. 978-1-4665-0991-7. 455.
2. Web site: Founding of ARL . www.arl. army.mil . Army Research Laboratory . 6 June 2018.
3. Web site: Gooch . William A. . The Design and Application of Titanium Alloys to U.S. Army Platforms -2010 . U.S. Army Research Laboratory . 6 June 2018.
4. Web site: Stan Abkowitz, '48 – MIT Technology Review . 18 October 2016 .
5. Web site: Stanley Abkowitz, 90; Titanium Industry Pioneer - International Titanium Association .
6. Long. M.. Rack. H.J.. 1998. Titanium alloys in total joint replacement—a materials science perspective. Biomaterials. 18. 19. 1621–1639. 10.1016/S0142-9612(97)00146-4. 9839998.
7. E.Y.. Gutmanas. 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. 10.1023/B:JMSM.0000021096.77850.c5. 15332594. 45437647.
8. http://bqw.csstgc.com.cn/userfiles/04d50d7598c54325a4f12f868710a407/files/teckSolution/2019/11/Standard%20Specification%20for%20Wrought%20Titanium-6Aluminum-4Vanadium%20Alloy%20for%20Surgical%20Implant%20Applications.pdf Standard Specification for Wrought Titanium-6Aluminum-4Vanadium Alloy for Surgical Implant Applications (UNS R56400)
9. Web site: Titanium Ti-6Al-4V (Grade 5), Annealed. asm.matweb.com. ASM Aerospace Specification Metals, Inc.. 14 March 2017.
10. Web site: Titanium Alloy Ti 6Al-4V Technical Data Sheet. cartech.com. Carpenter Technology Corporation. 14 March 2017.
11. Web site: AZoM Become a Member Search... Search Menu Properties This article has property data, click to view Titanium Alloys - Ti6Al4V Grade 5. www.azom.com. 30 July 2002 . AZO Materials. 14 March 2017.
12. Book: Donachie, Matthew J.. Titanium : a technical guide. limited. 2000. ASM International. 9781615030620. 2nd. Materials Park, OH. 13–15. 713840154.
13. Web site: ASM Material Data Sheet. 2020-06-20. asm.matweb.com.
14. Yang. Xiaoping. Liu. C. Richard. 1999-01-01. Machining Titanium and Its Alloys. Machining Science and Technology. 3. 1. 107–139. 10.1080/10940349908945686. 1091-0344.
15. Web site: AF066 crash investigation results. BEA. September 2020.
16. Book: https://onlinelibrary.wiley.com/doi/abs/10.1002/9781119296126.ch169 . 10.1002/9781119296126.ch169 . On the Cyclic Fatigue and Dwell Fatigue Crack Growth Response of Ti-6Al-4V . Proceedings of the 13th World Conference on Titanium . 2016 . Pilchak . Adam L. . Hutson . Alisha . Porter . W. John . Buchanan . Dennis . John . Reji . 993–998 . 9781119296126 .
17. Book: ASM Committee. Titanium: A Technical Guide. ASM International. 2000. 22–23. The Metallurgy of Titanium.
18. The Boeing 787 Dreamliner: More Than an Airplane . May 25, 2005 . Hawk, Jeff . AIAA/AAAF Aircraft Noise and Emissions Reduction Symposium . American Institute of Aeronautics and Astronautics. July 15, 2007 . https://web.archive.org/web/20070808001501/http://www.aiaa.org/events/aners/Presentations/ANERS-Hawk.pdf . August 8, 2007.
19. Web site: Composites in Airbus - A Long Story of Innovations and Experiences . 2008 . Global Investor Forum . Airbus . Guy Hellard . 30 January 2019 . https://web.archive.org/web/20161004204641/https://www.airbusgroup.com/dam/assets/airbusgroup/int/en/investor-relations/documents/2008/presentations/GIF2008/gif2008_workshop_composites_hellard.pdf . 4 October 2016 . dead.
20. Web site: Ti6Al4V Titanium Alloy. Arcam. 2015-12-16. 2020-02-15. https://web.archive.org/web/20200215075815/http://www.arcam.com/wp-content/uploads/Arcam-Ti6Al4V-Titanium-Alloy.pdf. dead.
21. Web site: Ti64 Titanium Alloy Powder. Tekna.
22. Web site: Demystifying Titanium Alloys: TI 6-4 Grade 5 VS. TI 23 . Stanford Advanced Materials . June 30, 2024.
23. Book: Sorkin . G. . Lane . I.R. . Cavallaro . J.L. . 1982 . Titanium and Titanium Alloys . Williams . J.C . Springer . Ti-6A1-4V for Marine Uses . 2139–2147 . 10.1007/978-1-4757-1758-7_49. 978-1-4757-1760-0 .
24. Gurrappa . I. . 2003 . Characterization of titanium alloy Ti-6Al-4V for chemical, marine and industrial applications . Materials Characterization . 51 . 2–3 . 131–139 . 10.1016/j.matchar.2003.10.006.
25. Alijibori . H.S. . Alamiery . A. . Kadhum . A.A.H. . 2023 . Advances in corrosion protection coatings: A comprehensive review . Int. J. Corros. Scale Inhib. . 12 . 4 . 1476–1520 . 10.17675/2305-6894-2023-12-4-6. free .