1. Material Composition & Manufacturing Process

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:

1. 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
  2. Homogenization:
• 480-500°C for 12-24 hours
• Uniform temperature control: ±5°C
• Microstructural equilibration
• Cu-rich phase dissolution
  3. 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
  4. Solution Heat Treatment:
• 490-500°C for 1 hour (diameter-dependent)
• Temperature uniformity: ±3°C
• Rapid transfer to quenching medium
  5. Quenching:
• Cold water (5-30°C)
• Agitation for uniform cooling
• Maximum transfer time: 15 seconds
• Minimum cooling rate: 100°C/sec at surface
  6. Cold Straightening:
• Hydraulic press straightening
• Maximum 1-2% cold work
• Residual stress minimization
  7. 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.

2. Mechanical Properties of 2024 Aluminum Bar

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

3. Microstructural Characteristics

Key Microstructural Features:

1. 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
  2. Precipitate Distribution:
• Al₂Cu (θ/θ’) strengthening precipitates: 5-50nm
• Al₂CuMg (S-phase) precipitates
• Al₁₂Mn₃Si dispersoids: 50-200nm
• Al₇Cu₂Fe intermetallics: Controlled size and distribution
  3. Texture Development:
• Strong <111> and <100> fiber textures
• Deformation texture retained after heat treatment
• Texture intensity: 3-8× random
  4. 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

4. Dimensional Specifications & Tolerances

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

5. Temper Designations & Heat Treatment Options

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

6. Machining & Fabrication Characteristics

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)

7. Corrosion Resistance & Protection Systems

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

8. Physical Properties for Engineering Design

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)

9. Quality Assurance & Testing

Standard Testing Procedures:

1. Chemical Composition:

• Optical emission spectroscopy
• Verification of all major elements and impurities
  2. Mechanical Testing:
• Tensile testing (longitudinal and transverse)
• Hardness testing (Brinell or Rockwell)
• Electrical conductivity for temper verification
  3. Dimensional Inspection:
• Diameter/dimensions at multiple locations
• Straightness verification
• Surface finish measurement
  4. Visual Inspection:
• Surface defects assessment
• Finish quality verification
  5. 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

10. Applications & Design Considerations

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