Aluminum CNC machining prototype parts made of aluminum billet 6061-T6 Vs. 6061-T651

Brieft summary of the chemical and mechanical differences between aluminum 6061-T6 and 6061-T651, along with their usage applications.

Chemical Composition

Both aluminum 6061-T6 and 6061-T651 have similar chemical compositions, primarily consisting of:

• Silicon (Si): 0.4 – 0.8%
• Iron (Fe): 0.0 – 0.7%
• Copper (Cu): 0.15 – 0.4%
• Manganese (Mn): 0.15 – 0.8%
• Magnesium (Mg): 0.8 – 1.2%
• Chromium (Cr): 0.04 – 0.35%
• Zinc (Zn): 0.0 – 0.25%
• Titanium (Ti): 0.0 – 0.15%
• Aluminum (Al): Balance

Mechanical Properties

• 6061-T6:
  • Yield Strength: ~276 MPa (40,000 psi)
  • Tensile Strength: ~310 MPa (45,000 psi)
  • Elongation: 10-12%
• 6061-T651:
  • Yield Strength: ~276 MPa (40,000 psi) (similar to T6)
  • Tensile Strength: ~310 MPa (similar to T6)
  • Elongation: 12-16% (higher than T6)

Key Differences

1. Stress Relief:
   • T651 undergoes additional stress-relieving processes, making it less prone to warping or cracking during machining compared to T6.
2. Machinability:
   • T651 is generally easier to machine due to reduced residual stresses, resulting in better surface finishes.
3. Ductility:
   • T651 has higher elongation, making it more ductile and suitable for applications involving bending or forming.

Usage Applications

• 6061-T6:
  • Commonly used in structural applications, aerospace components, automotive parts, and high-stress applications where maximum strength is required.
• 6061-T651:
  • Preferred for applications requiring improved machinability and stress relief, such as complex geometries, precision parts, and components that undergo further machining.

Conclusion: when selecting between 6061-T6 and 6061-T651, consider the mechanical properties and the specific application needs. T6 is best for strength-critical applications, while T651 is ideal for parts needing better machinability and ductility.