BOZE CNC Ti | Near-Alpha Alloy

Ti-6211 – Ti-6Al-2Nb-1Ta-0.8Mo Marine Grade Titanium Ti-6211

Ti-6Al-2Nb-1Ta-0.8Mo (Ti-6211, UNS R56210), also known as Ti-621/0.8 — a near-alpha titanium alloy originally developed by the U.S. Navy for deep-submergence pressure hulls. Its unique Nb+Ta stabilizer system delivers exceptional stress corrosion cracking (SCC) resistance in seawater, superior fracture toughness, and excellent weldability for thick-section marine structures.

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Entity Definition

What is Ti-6211 Titanium (Ti-6Al-2Nb-1Ta-0.8Mo)?

Ti-6Al-2Nb-1Ta-0.8Mo, commonly referred to as Ti-6211 or Ti-621/0.8, is a near-alpha titanium alloy originally developed by the U.S. Navy in the 1950s–1960s for deep-submergence pressure hull applications. Its distinctive composition combines 6% aluminum (alpha stabilizer) with niobium (2%), tantalum (1%), and molybdenum (0.8%) — the Nb+Ta combination providing exceptional resistance to stress corrosion cracking (SCC) in marine environments. This alloy is renowned for its outstanding fracture toughness, excellent weldability for heavy sections, and robust performance under high hydrostatic pressure at ocean depths.

Classification

Near-Alpha Titanium Alloy (α-rich)
UNS Number

UNS R56210

Common Names

Ti-6Al-2Nb-1Ta-0.8Mo Ti-6211 Ti-621/0.8 UNS R56210

Key Characteristics

  • Exceptional stress corrosion cracking (SCC) resistance in seawater and saline environments
  • Superior fracture toughness with high safety margins for pressure-critical applications
  • Excellent weldability — low crack sensitivity in heat-affected zones for thick-section welding
  • Good elevated-temperature strength and creep resistance
  • Excellent formability and machinability compared to beta-rich titanium alloys
  • Designed specifically for high-pressure deep-sea service conditions
Applicable Standards

Applicable Standards

Ti-6211 titanium conforms to the following international material standards:

MIL-T-9047 — Titanium and Titanium Alloy Plate, Sheet, and Strip
AMS 4904 — Titanium Alloy Plate, Sheet, and Strip, Ti-6Al-2Nb-1Ta-0.8Mo
ASTM B265 — Sheet, Strip, and Plate (cross-reference)
ASTM B348 — Bars and Billets (cross-reference)
ASTM B381 — Forgings (cross-reference)
NACE MR0175 / ISO 15156 — Oilfield Equipment (marine service)
ABS (American Bureau of Shipping) — Marine Vessel and Submersible Rules
Naval Sea Systems Command (NAVSEA) — Submarine Pressure Hull Specifications
Material Properties

Mechanical & Physical Properties

Typical room-temperature properties for Ti-6211 (annealed condition, unless noted):

Tensile Strength (min, annealed) 895 MPa (130 ksi)
Yield Strength 0.2% Offset (min, annealed) 828 MPa (120 ksi)
Elongation (min, annealed) 10%
Reduction of Area 25%
Density 4.48 g/cm³ (0.162 lb/in³)
Elastic Modulus 110 GPa (16.0 × 10⁶ psi)
Melting Point 1,660°C (3,020°F)
Thermal Conductivity 7.0 W/(m·K)
Fracture Toughness KIC (annealed) 85–110 MPa√m
Stress Corrosion Cracking Threshold KISCC (seawater) ≥ 60 MPa√m
Fatigue Strength (10⁷ cycles, R=0.1) 450–520 MPa
Hardness ≤ 36 HRC
Max Service Temperature 400°C (750°F)
Processing Methods

Available Processing Methods

Ti-6211 can be processed using the following manufacturing techniques:

CNC machining — Good with sharp carbide tools, rigid setups, and adequate coolant flow
5-axis CNC machining — Suitable for complex pressure vessel components and submersible structures
Wire EDM — Ideal for precision cutouts and thick-section profiling
TIG welding — Excellent with matching filler metal; low HAZ crack sensitivity enables heavy-section welding
Laser beam welding — Good weld quality with proper joint design and inert gas shielding
Electron beam welding — Excellent for deep-penetration, narrow-HAZ welds in vacuum
Submerged arc welding — Applicable for very heavy plate sections in pressure hull fabrication
Vacuum annealing — At 700–800°C (1,300–1,475°F) to relieve residual stresses
Hot forming — At 800–900°C (1,475–1,650°F) for complex shapes
Forging — Alpha-beta forging at 950–1,050°C (1,740–1,920°F)
Hot isostatic pressing (HIP) — At 920°C / 100 MPa to eliminate internal porosity
Downstream Products

Typical Products & Components

Ti-6211 is commonly fabricated into the following downstream products:

Deep-submergence pressure hulls — manned and unmanned submersible shells
Marine pressure vessels — hyperbaric chambers, deep-sea storage tanks, hydraulic cylinders
Naval ship structures — waterjet propulsion components, sonar domes, rudder assemblies
Submarine ballast and trim system components
Oceanographic instrument housings and sensor pods
Undersea pipeline connectors and riser systems
Offshore oil & gas subsea tree equipment
Thick-plate welded assemblies for critical marine structural applications
High-performance marine fastener systems — bolts, studs, and connectors
Additive manufacturing (3D printing) — spherical powder for complex deep-sea components
Industries

Primary Industries

Ti-6211 serves as a material of choice across these industries:

Deep-sea exploration — Manned and ROV/AUV submersible hulls and pressure vessels
Ocean engineering — Offshore platforms, riser systems, subsea manifolds
Additive manufacturing — 3D printed deep-sea and aerospace components
Alternative Materials

Alternative Materials

Depending on application requirements, Ti-6211 may be substituted by:

Ti-6Al-2Sn-4Zr-2Mo (Grade 6242) — Higher-temperature creep resistance but not optimized for marine SCC performance
HY-80 / HY-100 Steel — Lower cost for pressure hulls but significantly heavier and susceptible to corrosion
Stainless Steel 316L — Lower cost for marine service but lower strength and fatigue life
Why BOZE CNC Ti

Why Choose Us for This Grade

BOZE CNC Ti is a precision manufacturer of Ti-6211 (Ti-6Al-2Nb-1Ta-0.8Mo) near-alpha titanium components for defense, deep-sea exploration, and marine engineering applications. Our AS9100D-certified facility sources 100% certified Ti-6211 plate, bars, and forgings, and transforms them into complex pressure vessel components, structural assemblies, and subsea hardware using state-of-the-art 5-axis CNC machining centers, precision turning, advanced TIG/laser welding, and wire EDM. Every component is produced under AS9100D and ISO 9001:2015 quality systems with full material traceability from mill to finished part. Our engineering team provides 24-hour DFM review and competitive quoting, backed by decades of metallurgical expertise in near-alpha titanium processing for critical marine service.

Frequently Asked Questions

Common questions from engineers about this titanium grade and our precision machining capabilities.

What is Ti-6211 (Ti-6Al-2Nb-1Ta-0.8Mo) titanium alloy?

Ti-6211, also known as Ti-621/0.8, is a near-alpha titanium alloy developed by the U.S. Navy for deep-submergence pressure hulls. Its unique niobium + tantalum stabilizer system provides exceptional resistance to stress corrosion cracking in seawater, combined with outstanding fracture toughness and excellent weldability for thick-section marine structures.

What makes Ti-6211 different from Grade 5 (Ti-6Al-4V) for marine applications?

While Grade 5 offers excellent general corrosion resistance, Ti-6211 is specifically formulated for the demanding conditions of deep-sea service. The Nb+Ta additions dramatically improve resistance to stress corrosion cracking (SCC) under sustained load in seawater — a critical failure risk for pressure vessels. Ti-6211 also exhibits superior fracture toughness (85–110 MPa√m) and significantly better weldability for thick-section welding.

What welding processes are suitable for Ti-6211? Can you weld thick plates?

Ti-6211 is one of the most weldable high-strength titanium alloys. TIG, laser beam, and electron beam welding are all applicable. Its low crack sensitivity in the heat-affected zone makes it particularly suitable for heavy-section (50 mm+) plate welding required for pressure hull fabrication. Matching filler metal with strict inert gas shielding is essential for all welding operations.

What machining capabilities do you have for Ti-6211 components?

We offer precision 5-axis CNC machining, CNC turning, and wire EDM for Ti-6211 components. Our DMG Mori and Mazak machining centers with high-pressure coolant systems can handle complex pressure vessel components and structural parts. CMM dimensional verification per AS9102 is available for all critical features.

Need Ti-6211 Marine Grade Titanium Components?

Our engineering team delivers precision-machined components in Ti-6211 (Ti-6Al-2Nb-1Ta-0.8Mo) Near-Alpha Titanium. Submit your RFQ for a competitive quote within 24–48 hours.

About Boze Titanium Manufacturing Center

One Metal. One Focus. Infinite Precision.

Founded in 2011 in Baoji's Titanium Valley, BOZE Metal is dedicated exclusively to titanium — from raw material to precision engineering. AS9100D, ISO 13485 & ISO 9001 certified with 500+ clients across Aerospace, Medical & Motorsport industries, we deliver end-to-end precision titanium CNC machining with full material traceability from source to component.

Boze CNC Ti is the dedicated titanium manufacturing center of Baoji Boze Metal Products Co., Ltd.

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