Introduction to Ti-6Al-4V Titanium Alloy

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Ti-6Al-4V, also known as Grade 5 titanium alloy, is one of the most popular titanium alloys used in a variety of applications. This article provides a comprehensive overview of Ti-6Al-4V, including its composition, properties, applications, specifications, pricing, handling and more.

Ti-6Al-4V Composition

Ti-6Al-4V is an alpha-beta titanium alloy containing 6% aluminum, 4% vanadium, 0.25% (maximum) iron, 0.2% (maximum) oxygen, and the remainder titanium. Here is the nominal composition of Ti-6Al-4V:

العنصرالوزن %
التيتانيومالرصيد
ألومنيوم5.5 – 6.75
Vanadium3.5 – 4.5
Iron≤ 0.3
Oxygen≤ 0.2

The aluminum stabilizes and strengthens the alpha phase, while vanadium enables beta phase formation. The combination of alpha and beta phases gives Ti-6Al-4V excellent strength, corrosion resistance and workability.

Ti-6Al-4V Properties

Ti-6Al-4V has the following properties that make it advantageous for aerospace, medical, marine and other applications:

الممتلكاتValue
الكثافة4.43 g/cm3
نقطة الانصهار1604 – 1660°C
Tensile Strength895 – 1170 MPa
Yield Strength825 – 1103 MPa
Elongation8 – 16%
Elastic Modulus114 GPa
قوة التعب400 – 500 MPa
صلابة الكسر55 – 115 MPa-m^1/2
مقاومة التآكلممتاز
Bio-compatibilityممتاز

Key features:

  • Lightweight with high strength-to-weight ratio
  • Withstands extreme temperatures
  • High fatigue strength
  • Resistant to corrosion, acids, chlorides
  • Compatible for implants and prosthetics

Ti-6Al-4V Applications

Ti-6Al-4V is used in the following major applications because of its unique combination of properties:

الصناعةالتطبيقات
الفضاءAircraft engine components, airframes, fasteners, hydraulic systems
الطب الحيويSurgical implants, orthopedic and dental prosthetics
البحريةPropellers, offshore platform rigs, pipelines, heat exchangers
المواد الكيميائيةTanks, pipes, valves, pumps, reaction vessels
السياراتValves, connecting rods, suspension springs
Power generationSteam turbine blades, waste incinerator parts, heat exchangers
السلع الرياضيةGolf clubs, bicycle frames, tennis rackets, hockey sticks

Ti-6Al-4V allows designing lighter, faster and more durable components and equipment.

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Introduction to Ti-6Al-4V Titanium Alloy 4

Ti-6Al-4V Specifications

Ti-6Al-4V is covered under the following specifications:

StandardTitle
AMS 4911Titanium 6Al-4V alloy, annealed sheet/strip/plate
ASTM B348Titanium and titanium alloy bars and billets
ASTM F1472Wrought titanium-6aluminum-4vanadium alloy for surgical implant applications
ASTM F1108Titanium-6Aluminum-4Vanadium alloy for surgical implants
AMS 4928Investment castings, corrosion resistant steel, high strength, vacuum melted, titanium alloys
AMS 4965Titanium alloy sheet, strip and plate 6Al -4V annealed
MSRR 9545Titanium alloy, sheet, strip and plate 6Al – 4V, annealed

These cover the alloy composition limits, mechanical properties, heat treatment, microstructure requirements, corrosion testing and other parameters.

Ti-6Al-4V Product Forms

Ti-6Al-4V is produced in the following forms, sizes, shapes and finishes:

نموذج المنتجSize Range
Sheet0.4 – 6.35 mm thickness
Plate6 – 250 mm thickness
BarUp to 650 mm diameter
RodUp to 650 mm diameter
Wire0.1 – 15 mm diameter
Tube2 – 300 mm diameter
CastingsCustom sizes and shapes
ForgingsCustom sizes and shapes

Finishes include hot rolled, cold rolled, annealed, polished, machined, pickled, descaled and more.

Ti-6Al-4V Grades

Ti-6Al-4V is covered under the following ASTM grades that differ in minimum tensile and yield strength levels:

ASTM GradeTensile Strength (min) MPaYield Strength (min) MPa
Grade 5895825
Grade 23965895
Grade 2411701103

Grade 5 Ti-6Al-4V provides the standard properties, while Grades 23 and 24 are high-strength variants.

Ti-6Al-4V Suppliers

Ti-6Al-4V is readily available from the following major titanium suppliers and distributors:

  • ATI
  • VSMPO-AVISMA
  • Western Metal Materials
  • Baoji Titanium Industry Co.
  • Western Superconducting Technologies
  • Titanium Industries

Global titanium sponge production capacity was estimated around 330,000 tons in 2020, with much of this used for Ti-6Al-4V manufacturing.

Ti-6Al-4V Pricing

As of 2023, Ti-6Al-4V pricing is approximately:

نموذج المنتجPrice Range per kg
Sheet/Plate$15 – $50
Bar/Rod$15 – $35
Wire$25 – $60
Tube$20 – $45
Castings$25 – $100
Forgings$25 – $100

Prices vary based on size, thickness, grade, quantity ordered, processing, lead times and supply-demand dynamics. Mills generally offer volume-based discounts.

Ti-6Al-4V Machining

Ti-6Al-4V has low thermal conductivity so heat dissipates slowly during machining. Recommended techniques include:

  • Use rigid setups to minimize vibration
  • Employ high cutting speeds with slow feeds/depths
  • Use high positive rake tools with sharp cutting edges
  • Apply heavy flood cooling using emulsions
  • Control chip formation to avoid work hardening

Carbide, cermet, CBN and diamond tools are commonly used. Coolants containing sulfur should be avoided.

Ti-6Al-4V Welding

Ti-6Al-4V can be welded using GTAW, PAW, LBW and other methods. Precautions include:

  • Maintain inert gas shielding to prevent oxidation
  • Limit heat input to avoid cracks and loss of strength
  • Post weld heat treatment may be required
  • Match composition of filler metal to base metal

Common filler metals include ER5356 and ER2319.

Ti-6Al-4V Heat Treatment

Ti-6Al-4V can be heat treated to modify its microstructure and mechanical properties:

العمليةTypical Heat Treatment
Annealing705°C for 2 hours, air cool
Stress relieving480 – 650°C for 2 – 4 hours, air cool
Solution treatment930 – 955°C for 1 hour, water quench
Aging480 – 595°C for 2 – 8 hours, air cool

Annealing improves ductility and machinability. Aging increases strength. Proper heat treatment is critical for optimizing properties.

Ti-6Al-4V Forging

Forging makes solid Ti-6Al-4V components with excellent fatigue strength. Key forging aspects:

  • Heat slowly to forging temperature 700 – 850°C
  • Multiple forgings with intermediate anneals may be required
  • Hot trim forgings before annealing
  • Anneal after forging to relieve stresses
  • Machine allowance should be 1 – 2 mm

Closed die forging under hammers or presses produces the best properties. Titanium requires heavy forces for forging.

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Ti-6Al-4V Casting

Investment casting of Ti-6Al-4V allows making complex shapes with good surface finishes:

  • Use multiple gates and risering for sound castings
  • Maintain inert atmosphere during melting and casting
  • Hot isostatic pressing (HIP) helps eliminate internal defects
  • Chemically mill surface to remove alpha case
  • Anneal castings to improve ductility

Cast Ti-6Al-4V has lower fatigue strength than wrought products.

Ti-6Al-4V Joining

Common Ti-6Al-4V joining methods include:

  • Fusion welding (GTAW, PAW, LBW, electron beam)
  • Brazing using Ti-Cu-Ni filler metals
  • Mechanical fastening, bolts, rivets
  • Adhesive bonding using epoxy or polyimide

Joint strength depends on process used. Matching alloy composition and minimizing contamination are key.

Ti-6Al-4V Handling

Recommended handling practices for Ti-6Al-4V:

  • Use clean gloves to prevent contamination from skin oils and salts
  • Avoid contact with hazardous metals like cadmium, mercury, gallium
  • Prevent exposure to acids, chlorides and other corrosive chemicals
  • Store in cool, dry, inert environments away from moisture
  • Protect from scratches, nicks, dents during transport and storage

Titanium dust is highly flammable and sensitive to static discharge. Follow proper grounding, ventilation and cleaning procedures.

Ti-6Al-4V Safety

Key safety measures for handling titanium alloys:

  • Wear appropriate PPE – eye protection, dust mask, gloves
  • Use sufficient local exhaust ventilation when machining
  • Avoid breathing fumes from welding or thermal cutting
  • Prevent accumulation of chips and dust
  • Ensure adequate fire extinguishing equipment is available
  • Follow safe practices for compressed gas cylinders and cryogens

Titanium itself has low toxicity but processing can generate hazardous particulates.

Ti-6Al-4V Inspection

Ti-6Al-4V parts are typically inspected using:

  • Visual and macro examination for defects
  • Liquid penetrant testing to detect surface flaws
  • Ultrasonic inspection for internal integrity
  • Radiographic testing using X-ray or gamma ray
  • Eddy current methods to identify cracks and voids
  • Proof testing and pressure testing finished components

Grain structure, alpha case depth, surface finish and dimensions are also commonly checked.

Ti-6Al-4V Quality Assurance

Ti-6Al-4V suppliers should have quality systems certified to:

  • ISO 9001 Quality Management
  • AS9100 Aerospace standard
  • ISO 13485 Medical devices standard
  • NADCAP Special processes like heat treatment and NDT

Airframe and medical applications have additional regulatory requirements.

Advantages of Ti-6Al-4V

  • Excellent strength-to-weight ratio
  • Withstands extreme temperatures
  • Resists corrosion in many environments
  • Bio-compatible for implants
  • Can be heat treated to tailor properties
  • Readily formed and machined
  • Available from many qualified suppliers

Limitations of Ti-6Al-4V

  • More expensive than steels and aluminum alloys
  • Lower stiffness than steel
  • Not heat treatable to full hardness
  • Subject to galling and seizing during machining
  • Section sizes are limited by forging and casting capabilities
  • Melting requires controlled inert atmosphere
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Introduction to Ti-6Al-4V Titanium Alloy 5

Ti-6Al-4V vs. Other Titanium Alloys

How does Ti-6Al-4V compare to other popular titanium alloys?

سبيكةالقوةمقاومة التآكلالتكلفةUse Cases
Ti-6Al-4VعاليةممتازمعتدلAerospace, marine, biomedical
CP TitaniumمتوسطممتازمنخفضةChemical, seawater systems
Ti-10V-2Fe-3Alعالية جداًجيدعاليةAerospace fasteners, rigging
Ti-3Al-2.5VمتوسطممتازمعتدلJet engines, airframes
Ti-13V-11Cr-3Alعاليةممتازعالية جداًAerospace components

Ti-6Al-4V provides the best all-round properties at a reasonable cost. Other alloys offer higher strength or corrosion performance for specialized applications.

التعليمات

Q: What is Ti-6Al-4V used for?

A: Ti-6Al-4V is widely used in aerospace, marine, chemical processing, biomedical, and consumer applications where high strength, low weight, and corrosion resistance are needed.

Q: Is Ti-6Al-4V stronger than steel?

A: Yes, Ti-6Al-4V has a higher strength-to-weight ratio than most steels, but lower stiffness. It is about 60% heavier than aluminum.

Q: Is Ti-6Al-4V compatible for medical implants?

A: Yes, Ti-6Al-4V has excellent biocompatibility and commonly used for joint replacements, dental implants, pacemakers, and fracture fixation devices.

Q: Does Ti-6Al-4V require heat treatment?

A: Ti-6Al-4V can be heat treated to modify its properties. Solution treatment and aging can significantly increase its strength.

Q: What is the difference between Grade 5 and Grade 23 Ti-6Al-4V?

A: Grade 5 is the standard alloy with 895 MPa minimum tensile strength. Grade 23 has higher strength requirements of 965 MPa minimum.

Q: What is the corrosion resistance of Ti-6Al-4V?

A: Ti-6Al-4V has excellent corrosion resistance to most acids, chlorides, and saltwater environments. Its passivity is maintained across a wide pH range.

Q: Can you weld Ti-6Al-4V?

A: Yes, welding methods like GTAW, LBW, and PAW can be used to weld Ti-6Al-4V. Proper procedures should be followed to ensure joint integrity.

Q: What is the cost of Ti-6Al-4V compared to other metals?

A: On a per pound basis, Ti-6Al-4V is more expensive than steels and aluminum alloys, but cheaper than exotic alloys like Inconel or Hastelloy.

Q: What are some alternatives to Ti-6Al-4V?

A: For aerospace use, Ti-10V-2Fe-3Al provides higher strength. For corrosion resistance, CP Titanium or Ti-3Al-2.5V are excellent. Ti-1023 and Ti-5553 are newer high-strength alloys.

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