2024 aluminum alloy (AMS 4120, ASTM B211) is a high-strength aircraft-grade aluminum-copper alloy prized for its excellent strength-to-weight ratio, superior machinability, and good fatigue performance. The bar stock configuration offers optimized properties for critical structural components:

Primary Alloying Elements:

Copper (Cu): 3.8-4.9% (primary strengthening element)

Magnesium (Mg): 1.2-1.8% (precipitation hardening)

Manganese (Mn): 0.3-0.9% (grain structure control)

Silicon (Si): ≤0.5% (improves castability)

Base Material:

Aluminum (Al): ≥90.7% (balance)

Controlled Impurities:

Iron (Fe): ≤0.5% max

Zinc (Zn): ≤0.25% max

Titanium (Ti): ≤0.15% max

Chromium (Cr): ≤0.10% max

Other elements: ≤0.05% each, ≤0.15% total

Premium Manufacturing Process:

Billet Preparation:

Primary high-purity aluminum (99.7% minimum)

Precise alloying element additions

Filtration through ceramic foam filters

Degassing treatment (hydrogen < 0.15 ml/100g)

Direct-chill semi-continuous casting

Homogenization:

480-500°C for 12-24 hours

Uniform temperature control: ±5°C

Microstructural equilibration

Cu-rich phase dissolution

Extrusion:

Preheating to 370-400°C

Lubrication optimization

Computerized extrusion force monitoring

Exit temperature control: 450-480°C

Cooling rate optimization for property development

Straightening within 4mm/m

Solution Heat Treatment:

490-500°C for 1 hour (diameter-dependent)

Temperature uniformity: ±3°C

Rapid transfer to quenching medium

Quenching:

Cold water (5-30°C)

Agitation for uniform cooling

Maximum transfer time: 15 seconds

Minimum cooling rate: 100°C/sec at surface

Cold Straightening:

Hydraulic press straightening

Maximum 1-2% cold work

Residual stress minimization

Artificial Aging:

T3: Natural aging at room temperature

T351: Stress relief + natural aging

T4: Solution heat treated + natural aging

T6: Artificial aging at 190°C for 12 hours

Full process traceability with lot-specific quality documentation.

 

 

 

Property	T351 (min)	T351 (typical)	T6 (min)	T6 (typical)	Test Method
Ultimate Tensile Strength	425 MPa	440-470 MPa	440 MPa	460-490 MPa	ASTM E8
Yield Strength (0.2%)	290 MPa	310-345 MPa	345 MPa	360-400 MPa	ASTM E8
Elongation (2 inch)	10%	12-17%	5%	6-10%	ASTM E8
Hardness (Brinell)	110 HB	115-125 HB	120 HB	125-135 HB	ASTM E10
Fatigue Strength (5×10⁸)	130 MPa	140-150 MPa	120 MPa	125-140 MPa	ASTM E466
Shear Strength	270 MPa	285-300 MPa	280 MPa	290-310 MPa	ASTM B769
Fracture Toughness (K₁c)	26 MPa√m	28-32 MPa√m	20 MPa√m	22-25 MPa√m	ASTM E399
Modulus of Elasticity	73.1 GPa	73.1 GPa	73.1 GPa	73.1 GPa	ASTM E111

Property Distribution:

Longitudinal to transverse property ratio: 1.00:0.85-0.90

Variation across diameter: <5% for bars up to 100mm

Core to surface hardness variation: <8 HB

Property retention after thermal exposure: Excellent below 100°C

 

Key Microstructural Features:

Grain Structure:

Elongated grains in extrusion direction

ASTM grain size 5-7 (50-70μm)

Aspect ratio: 2:1 to 5:1

Subgrain development in T351 temper

Precipitate Distribution:

Al₂Cu (θ/θ’) strengthening precipitates: 5-50nm

Al₂CuMg (S-phase) precipitates

Al₁₂Mn₃Si dispersoids: 50-200nm

Al₇Cu₂Fe intermetallics: Controlled size and distribution

Texture Development:

Strong <111> and <100> fiber textures

Deformation texture retained after heat treatment

Texture intensity: 3-8× random

Special Features:

Recrystallization controlled by Mn dispersoids

Natural aging involves GP zone formation

T6 temper: θ’ (Al₂Cu) precipitate dominance

Precipitate-free zones near grain boundaries: <50nm

 

 

 

Parameter	Standard Range	Precision Tolerance	Commercial Tolerance	Test Method
Diameter (Round)	10-300 mm	±0.15mm up to 30mm	±0.25mm up to 30mm	Micrometer
		±0.5% above 30mm	±1.0% above 30mm
Width (Rectangle)	10-250 mm	±0.20mm up to 50mm	±0.30mm up to 50mm	Caliper
		±0.4% above 50mm	±0.8% above 50mm
Length	2000-6000 mm	±3mm	±6mm	Tape measure
Straightness	N/A	0.5mm/m	1.0mm/m	Straightedge
Twist (Rectangular)	N/A	2° max per meter	4° max per meter	Protractor
Surface Roughness	N/A	3.2 μm Ra max	6.3 μm Ra max	Profilometer

Standard Available Forms:

Round Bar: Diameters 10-300mm

Hexagonal Bar: Across flats 10-100mm

Square Bar: Side dimensions 10-150mm

Rectangular Bar: Width up to 250mm, thickness from 10mm

Cut-to-length service available

 

 

 

Temper Code	Process Description	Optimal Applications	Key Characteristics
T351	Solution heat treated, stress relieved by stretching (1-3%), naturally aged	Aerospace structural components, machined parts	Excellent machinability, good strength-toughness balance
T4/T451	Solution heat treated, naturally aged	Parts requiring maximum formability	Best formability, moderate strength
T6/T651	Solution heat treated, artificially aged	Maximum strength applications	Highest strength, reduced ductility
T861	Solution heat treated, cold worked, artificially aged	Highly stressed components	High strength with good SCC resistance
T3	Solution heat treated, cold worked, naturally aged	General purpose applications	Good balance of properties

 

Temper Selection Guidance:

T351: Optimal for parts machined from bar stock

T6: When maximum strength is required

T4: When post-forming operations are needed

T861: For components exposed to high stress in corrosive environments

 

 

 

Operation	Tool Material	Recommended Parameters	Comments
Turning	Carbide, PCD	Vc=300-600 m/min, f=0.1-0.3 mm/rev	Excellent chip breaking
Drilling	HSS-Co, Carbide	Vc=70-120 m/min, f=0.2-0.4 mm/rev	Good hole quality
Milling	Carbide, PCD	Vc=300-700 m/min, fz=0.1-0.3 mm	Climb milling preferred
Tapping	HSS-E, TiN coated	Vc=15-25 m/min	Excellent thread quality
Reaming	Carbide, PCD	Vc=40-80 m/min, f=0.2-0.5 mm/rev	H7 tolerance achievable
Deep Drilling	Carbide, HSS-Co	Vc=60-90 m/min, pecking cycle	Excellent chip evacuation

 

Fabrication Guidance:

Machinability Rating: 70% (1100 aluminum = 100%)

Surface Finish: Excellent (Ra 0.8-3.2μm achievable)

Chip Formation: Short to medium chips

Coolant: Water-soluble emulsion preferred (8-10% concentration)

Tool Wear: Moderate with proper parameters

Burr Formation: Minimal with sharp tooling

Cold Working: Good formability in T4 condition

Hot Working: 350-450°C recommended temperature range

Weldability: Limited (pre-welding cleaning critical)

 

 

 

Environment Type	Resistance Rating	Protection Method	Expected Performance
Industrial Atmosphere	Moderate	Anodizing + paint	5-10 years with maintenance
Marine Environment	Poor	Anodizing + chromate + paint	3-5 years with maintenance
High Humidity	Fair	Anodizing Type II	2-3 years without additional protection
Stress Corrosion	Poor in T351, Better in T861	Shot peening + protection	Application specific
Exfoliation	Fair to Good	Proper heat treatment	T7x tempers preferred for critical apps

 

Surface Protection Options:

Anodizing:

Type II (Sulfuric): 10-25μm thickness

Type III (Hard): 25-75μm thickness

Chromic: 2-7μm (aerospace applications)

Conversion Coatings:

Chromate per MIL-DTL-5541 Class 1A

Non-chromium alternatives available

Painting Systems:

Epoxy primer + polyurethane topcoat

Aerospace-qualified systems available

Mechanical Protection:

Shot peening for enhanced fatigue and SCC resistance

Burnishing for improved surface finish

 

 

 

Property	Value	Design Consideration
Density	2.78 g/cm³	Weight calculation for components
Melting Range	502-638°C	Heat treatment limitations
Thermal Conductivity	120-150 W/m·K	Thermal management design
Electrical Conductivity	30-40% IACS	Electrical applications design
Specific Heat	875 J/kg·K	Thermal mass calculations
Thermal Expansion (CTE)	23.2 ×10⁻⁶/K	Thermal stress analysis
Young’s Modulus	73.1 GPa	Deflection and stiffness calculations
Poisson’s Ratio	0.33	Structural analysis parameter
Machinability Rating	70% (1100=100%)	Manufacturing planning

 

Design Considerations:

Operating Temperature Range: -80°C to +120°C

Property Retention: Excellent below 100°C

Electrical Conductivity: 30% IACS (T3), 40% IACS (T6)

Stress Relaxation: Minimal below 100°C

Magnetic Properties: Non-magnetic

Damping Capacity: Low (typical of aluminum alloys)

 

Standard Testing Procedures:

Chemical Composition:

Optical emission spectroscopy

Verification of all major elements and impurities

Mechanical Testing:

Tensile testing (longitudinal and transverse)

Hardness testing (Brinell or Rockwell)

Electrical conductivity for temper verification

Dimensional Inspection:

Diameter/dimensions at multiple locations

Straightness verification

Surface finish measurement

Visual Inspection:

Surface defects assessment

Finish quality verification

Specialized Testing (When Required):

Ultrasonic inspection per AMS-STD-2154

Penetrant inspection

Grain flow evaluation

Microstructural examination

Standard Certifications:

Mill Test Report (EN 10204 3.1)

Chemical analysis certification

Mechanical properties certification

Heat treatment certification

Dimensional inspection report

 

 

 

Primary Applications:

Aircraft landing gear components

Aerospace fittings and connectors

High-strength structural elements

Critical automotive components

Defense industry applications

Precision machine parts

Mold tooling components

High-performance bolts and fasteners

Hydraulic system components

Connecting rods and drive shafts

Design Advantages:

Excellent strength-to-weight ratio

Superior machinability for complex parts

Good fatigue performance

High fracture toughness in T351 condition

Dimensional stability after machining

Suitable for critical load-bearing applications

Good wear resistance with appropriate surface treatments

Proven history in aerospace applications

Predictable and consistent properties

Widely available in various sizes and forms