Material Family

Nickel-Copper-Aluminum-Titanium Alloy (Precipitation-Hardenable)

A high-strength version of the Monel family, gaining properties via heat treatment.

Common Supply Conditions

1. Solution Annealed (Soft Condition): For all machining, forging, and welding. 2. Solution Treated & Aged (STA): Supplied in the final high-strength condition.

Most bar for fabrication is supplied Solution Annealed; final aging is done post-machining. STA bar is for parts requiring no further heat treatment.

Common Forms (Bar)

Hot Rolled, Forged, or Cold Drawn Rounds, Hexagons. Also as Forging Billet for critical components.

Typically supplied as round bar for machining into high-strength components.

Chemical Composition (Typical wt.%)

Ni: ≥ 63.0 (Balance)
Cu: 27.0 - 33.0
Al: 2.30 - 3.15
Ti: 0.35 - 0.85
Fe: 2.0 max
Mn: 1.5 max
C: ≤ 0.25

The additions of Aluminum (Al) and Titanium (Ti) enable age-hardening by forming the γ' (Ni₃(Al,Ti)) strengthening precipitates.

Mechanical Properties (Typical)

Solution Annealed (As-Supplied):
• Tensile: 620 - 790 MPa
• Yield: 210 - 480 MPa
• Elongation: 35 - 45%
After Full Aging (Aged - ASTM B865):
• Tensile: 965 - 1200 MPa
• Yield: 690 - 965 MPa
• Elongation: 20 - 30%

The dramatic strength increase after aging is the core value. Achieves strength similar to alloy steel while being corrosion-resistant.

Physical Properties

Density: 8.44 g/cm³
Melting Range: 1315 - 1350 °C
Useful Service Range: Cryogenic to about 480°C (900°F), beyond which overaging occurs.

Maintains its enhanced strength in typical marine and downhole environments.

Key Performance Attributes

• High Strength-to-Weight Ratio, Excellent Fatigue Strength, and Low Magnetic Permeability.

• Excellent resistance to seawater and marine atmospheres (similar to Monel 400). Resists chloride stress corrosion cracking.
• Good resistance to hydrofluoric acid, alkalis, and many organic acids.

• Poor resistance to oxidizing acids (e.g., nitric acid).

Combines marine-grade corrosion resistance with the strength of steel.

Key Standards (Bar)

ASTM B865 / ASME SB-865 (Precipitation Hardening Nickel-Copper-Aluminum Alloy Rod, Bar, and Wire - for Solution Heat Treated material), AMS 4676 (Aerospace)

ASTM B865 is the primary specification for solution-annealed bar.

Heat Treatment (Aging)

Standard aging: 595°C (1100°F) for 16-20 hours, air cool. Sometimes a two-step age is used. For Solution Annealed bar, this is performed after all machining is complete.

This aging treatment is essential to develop the high strength and hardness.

Machinability

Machinability (Annealed): ~35%. Machinable with techniques for nickel alloys; tough and work-hardening.
Machinability (Aged): Extremely difficult; should be avoided. All heavy machining must be done in the soft, solution-annealed condition.

The "machine soft, then age harden" sequence is critical for manufacturing complex parts.

Typical Bar Applications

• Marine Engineering: Propeller shafts, pump rods, fasteners (bolts, studs), valve stems for seawater systems, boat shafting.
• Oil & Gas: Non-magnetic drill collars, wellhead components, springs, and instruments for sour service.
• Aerospace & Defense: High-strength fasteners, precision springs, seals.
• Chemical Processing: High-strength shafts, impellers, and wear sleeves for corrosive services.

The go-to bar material for critical, high-strength rotating components and fasteners in seawater and sour service environments.