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 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

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.^[9][10][11] Aluminum stabilizes the alpha phase, while vanadium stabilizes the beta phase.^[12][13]

	Density	Young's Modulus	Shear Modulus	Bulk Modulus	Poisson's Ratio	Tensile Yield Stress	Tensile Ultimate Stress	Hardness	Uniform Elongation
Min	4.429 g/cm3 (0.160 lb/cu in)	104 GPa (15.1×10^6 psi)	40 GPa (5.8×10^6 psi)	96.8 GPa (14.0×10^6 psi)	0.31	880 MPa (128,000 psi)	900 MPa (130,000 psi)	36 Rockwell C (Typical)	5%
Max	4.512 g/cm3 (0.163 lb/cu in)	113 GPa (16.4×10^6 psi)	45 GPa (6.5×10^6 psi)	153 GPa (22.2×10^6 psi)	0.37	920 MPa (133,000 psi)	950 MPa (138,000 psi)	--	18%

Ti-6Al-4V has a very low thermal conductivity at room temperature of 6.7 to 7.5 W/m·K,^[14][15] which contributes to its relatively poor machinability.^[15]

The alloy is vulnerable to cold dwell fatigue.^[16][17]

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 ${\displaystyle \alpha }$ and ${\displaystyle \beta }$ 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.^[18]

Applications

• Aerospace structures. The Boeing 787 is 15% titanium by weight,^[19] and the Airbus A350 is 14%.^[20]
• Biomedical implants and prostheses^[21]
• High-performance race cars
• High-end bicycles
• Additive manufacturing^[22]
• Apple iPhone 15 Pro (Max) case, iPhone 16 Pro and Pro Max cases and Apple Watch Series 10 titanium and Ultra 2 cases
• Marine applications: Ti-6Al-4V Grade 5 is extensively used in marine applications due to its exceptional corrosion resistance in seawater environments.^[23] 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.^[24][25] Its resistance to corrosion helps in reducing maintenance costs and extending the lifespan of marine equipment. ^[26]

Specifications

• UNS: R56400
• AMS Standard: 4928^[27]
• ASTM Standard: F1472
• ASTM Standard: B265 Grade 5^[28]

References

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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. "Stan Abkowitz, '48 – MIT Technology Review". 18 October 2016.
5. "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. doi:10.1016/S0142-9612(97)00146-4. PMID 9839998.
7. 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.
8. Standard Specification for Wrought Titanium-6Aluminum-4Vanadium Alloy for Surgical Implant Applications (UNS R56400)
9. "Titanium Ti-6Al-4V (Grade 5), Annealed". asm.matweb.com. ASM Aerospace Specification Metals, Inc. Retrieved 14 March 2017.
10. "Titanium Alloy Ti 6Al-4V Technical Data Sheet". cartech.com. Carpenter Technology Corporation. Retrieved 14 March 2017.
11. "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. 30 July 2002. Retrieved 14 March 2017.
12. 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
13. Donachie, Matthew J. (2000). Titanium : a technical guide (2nd ed.). Materials Park, OH: ASM International. pp. 13–15. ISBN 9781615030620. OCLC 713840154.
14. "ASM Material Data Sheet". asm.matweb.com. Retrieved 2020-06-20.
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16. BEA (September 2020). "AF066 crash investigation results" (PDF).
17. Pilchak, Adam L.; Hutson, Alisha; Porter, W. John; Buchanan, Dennis; John, Reji (2016). "On the Cyclic Fatigue and Dwell Fatigue Crack Growth Response of Ti-6Al-4V". Proceedings of the 13th World Conference on Titanium. pp. 993–998. doi:10.1002/9781119296126.ch169. ISBN 9781119296126.
18. ASM Committee (2000). "The Metallurgy of Titanium". Titanium: A Technical Guide. ASM International. pp. 22–23.
19. Hawk, Jeff (May 25, 2005). The Boeing 787 Dreamliner: More Than an Airplane (PDF). AIAA/AAAF Aircraft Noise and Emissions Reduction Symposium. American Institute of Aeronautics and Astronautics. Archived from the original (PDF) on August 8, 2007. Retrieved July 15, 2007.
20. Guy Hellard (2008). "Composites in Airbus - A Long Story of Innovations and Experiences" (PDF). Global Investor Forum. Airbus. Archived from the original (PDF) on 4 October 2016. Retrieved 30 January 2019.
21. "Ti6Al4V Titanium Alloy" (PDF). Arcam. Archived from the original (PDF) on 2020-02-15. Retrieved 2015-12-16.
22. "Ti64 Titanium Alloy Powder". Tekna.
23. "Demystifying Titanium Alloys: TI 6-4 Grade 5 VS. TI 23". Stanford Advanced Materials. Retrieved June 30, 2024.
24. Sorkin, G.; Lane, I.R.; Cavallaro, J.L. (1982). "Ti-6A1-4V for Marine Uses". In Williams, J.C (ed.). Titanium and Titanium Alloys. Springer. pp. 2139–2147. doi:10.1007/978-1-4757-1758-7_49. ISBN 978-1-4757-1760-0.
25. Gurrappa, I. (2003). "Characterization of titanium alloy Ti-6Al-4V for chemical, marine and industrial applications". Materials Characterization. 51 (2–3): 131–139. doi:10.1016/j.matchar.2003.10.006.
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27. SAE AMS4928W, Titanium Alloy Bars, Wire, Forgings, Rings, and Drawn Shapes 6Al - 4V Annealed, Warrendale, PA: SAE International, retrieved 28 September 2022
28. "§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