Ti-6Al-4V (TC4)
Introduction to Ti-6Al-4V (TC4)
Ti-6Al-4V, or TC4 or Grade 5 Titanium, is an alpha-beta titanium alloy reinforced with 6% aluminum and 4% vanadium. It is the most widely used titanium alloy due to its superior combination of strength, corrosion resistance, and thermal stability. Known for its excellent strength-to-weight ratio, TC4 is commonly adopted in aerospace, defense, motorsports, and medical industries.
Its high-performance characteristics make TC4 the go-to material for critical components produced via CNC machining services. Thanks to its balanced mechanical and thermal properties, CNC-machined titanium parts made from TC4 deliver consistent, reliable performance in extreme operating conditions.
Chemical, Physical, and Mechanical Properties of Ti-6Al-4V (TC4)
Chemical Composition (Typical)
Element | Composition Range (wt.%) | Key Role |
|---|---|---|
Titanium (Ti) | Balance (~90) | Base matrix with corrosion resistance |
Aluminum (Al) | 5.5–6.75 | Alpha stabilizer, increases strength |
Vanadium (V) | 3.5–4.5 | Beta stabilizer, enhances toughness and hardenability |
Iron (Fe) | ≤0.40 | Residual, affects strength |
Oxygen (O) | ≤0.20 | Improves strength, affects ductility |
Carbon (C) | ≤0.08 | Grain refinement, improves wear resistance |
Nitrogen (N) | ≤0.05 | Residual element, increases hardness |
Hydrogen (H) | ≤0.015 | Needs control to avoid embrittlement |
Physical Properties
Property | Value (Typical) | Test Standard/Condition |
|---|---|---|
Density | 4.43 g/cm³ | ASTM B311 |
Melting Range | 1604–1660°C | ASTM E1268 |
Thermal Conductivity | 6.7 W/m·K at 100°C | ASTM E1225 |
Electrical Resistivity | 1.71 µΩ·m at 20°C | ASTM B193 |
Thermal Expansion | 8.6 µm/m·°C | ASTM E228 |
Specific Heat Capacity | 560 J/kg·K at 20°C | ASTM E1269 |
Elastic Modulus | 113.8 GPa | ASTM E111 |
Mechanical Properties (Annealed Condition)
Property | Value (Typical) | Test Standard |
|---|---|---|
Tensile Strength | 895–960 MPa | ASTM E8/E8M |
Yield Strength (0.2%) | 830–900 MPa | ASTM E8/E8M |
Elongation | ≥10% | ASTM E8/E8M |
Hardness | 330–360 HB | ASTM E10 |
Creep Resistance | High | ASTM E139 |
Fatigue Resistance | Excellent | ASTM E466 |
Key Characteristics of Ti-6Al-4V (TC4)
High Strength-to-Weight Ratio: TC4 delivers up to 960 MPa tensile strength at a density of just 4.43 g/cm³, making it ideal for aerospace structures, fasteners, and performance parts.
Superior Corrosion and Oxidation Resistance: A passive titanium oxide layer ensures resistance in chloride, marine, and mildly acidic environments, with sustained performance up to 400°C in air.
Thermal Stability and Creep Resistance: TC4 maintains mechanical integrity at elevated temperatures (up to 400°C continuous service), suitable for jet engine components and exhaust systems.
Weldability and Biocompatibility: The alloy supports TIG/MIG welding and is non-toxic, making it a top choice for both structural aerospace frames and long-term implantable medical devices.
CNC Machining Challenges and Solutions for Ti-6Al-4V (TC4)
Machining Challenges
Extremely Low Thermal Conductivity: With only 6.7 W/m·K conductivity, heat accumulates at the cutting edge, promoting rapid tool degradation and dimensional instability.
Severe Work Hardening: TC4 quickly forms a hardened layer under the toolpath if chip load is insufficient, requiring continuous engagement and consistent chip thickness.
High Tool Wear: The alloy's abrasive intermetallic phases and oxide formation cause tool edge chipping and crater wear, especially under dry or low-coolant conditions.
Elastic Modulus-Driven Springback: With an elastic modulus of 113.8 GPa, deflection and elastic recovery challenge tight-tolerance operations, particularly for thin-walled geometries.
Optimized Machining Strategies
Tool Selection
Parameter | Recommendation | Rationale |
|---|---|---|
Tool Material | Coated carbide or ceramic inserts | Withstand high temperatures and abrasive wear |
Coating | AlTiN or TiSiN (PVD, 3–5 µm) | Improves thermal resistance and minimizes BUE |
Geometry | Sharp edge, positive rake | Reduces cutting force and heat input |
Cutting Speed | 30–70 m/min (roughing), 50–100 m/min (finishing) | Reduces work hardening and maintains tool life |
Feed Rate | 0.05–0.25 mm/rev | Maintains chip thickness to avoid glazing |
Coolant | Emulsified coolant at 100–150 bar | Ensures effective chip flushing and thermal control |
Ti-6Al-4V (TC4) Cutting Parameters (ISO 3685 Compliance)
Operation | Speed (m/min) | Feed (mm/rev) | Depth of Cut (mm) | Coolant Pressure (bar) |
|---|---|---|---|---|
Roughing | 20–30 | 0.15–0.25 | 2.0–3.0 | 70–100 (Through-tool) |
Finishing | 50–80 | 0.05–0.10 | 0.2–0.5 | 100–150 |
Surface Treatment for Ti-6Al-4V (TC4) Parts
Hot Isostatic Pressing (HIP) improves fatigue life by eliminating internal porosity, critical for pressure vessels and aerospace casings.
Heat Treatment allows aging and annealing at 700–850°C to optimize tensile strength and stress relief in high-load parts.
Superalloy Welding provides defect-free joints for TC4 aerospace assemblies, with filler wire (Ti-6Al-4V) matching base composition.
Thermal Barrier Coating (TBC) with YSZ ceramic layers enhances oxidation protection in engine or exhaust parts operating above 600°C.
CNC Machining ensures precision geometries with dimensional tolerance <±0.01 mm for TC4 aerospace and medical-grade parts.
Electrical Discharge Machining (EDM) is ideal for TC4 micro-holes and slots where mechanical tools may induce thermal cracks.
Deep Hole Drilling enables high L/D ratio channels for fuel injectors with internal Ra values ≤1.6 µm.
Material Testing, including fatigue, hardness, SEM microstructure, and ultrasonic flaw detection, verifies structural integrity for TC4 critical parts.
Material Testing and Analysis
Ti-6Al-4V testing includes hardness verification, fatigue life analysis, tensile properties at ambient and elevated temperatures, and non-destructive inspection per ASTM and ISO aerospace standards.
Industry Applications of Ti-6Al-4V (TC4)
Aerospace: Used in engine components, landing gear, structural frames, and airframe connectors due to its unmatched performance-to-weight ratio.
Defense: Fabricated into armor plates, missile casings, and UAV structures requiring lightweight durability under impact.
Medical: Utilized in orthopedic implants, spinal hardware, and dental prosthetics for its biocompatibility and osseointegration.
Motorsports: Components like valve springs, suspension systems, and exhausts demand TC4’s thermal fatigue resistance and lightweight durability.
Energy: Gas turbine blades, heat exchanger tubes, and chemical plant components benefit from TC4’s corrosion and creep resistance.
FAQs
What cutting strategies minimize tool wear when machining Ti-6Al-4V (TC4)?
How does TC4 perform under high thermal and mechanical stress in CNC applications?
What are the recommended surface treatments for fatigue-critical TC4 parts?
What tolerances can be reliably achieved when CNC machining TC4 titanium?
How does TC4 compare to commercially pure titanium grades in high-load environments?
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