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4145 (BAlSi-3) Aluminum

4145 aluminum is a 4000-series aluminum alloy. The main alloying addition is silicon. Cited properties are appropriate for the as-fabricated (no temper or treatment) condition. 4145 is the Aluminum Association (AA) designation for this material. In European standards, it will be given as EN AW-4145. BAlSi-3 is the AWS designation. Additionally, the UNS number is A94145.

It originally received its standard designation in 1957.

It has the lowest electrical conductivity and the lowest thermal conductivity among 4000-series alloys.

The graph bars on the material properties cards below compare 4145 aluminum to: 4000-series alloys (top), all aluminum alloys (middle), and the entire database (bottom). A full bar means this is the highest value in the relevant set. A half-full bar means it's 50% of the highest, and so on.

Mechanical Properties

Elastic (Young's, Tensile) Modulus

73 GPa 11 x 106 psi

Elongation at Break

2.2 %

Fatigue Strength

48 MPa 6.9 x 103 psi

Poisson's Ratio

0.33

Shear Modulus

28 GPa 4.0 x 106 psi

Shear Strength

69 MPa 9.9 x 103 psi

Tensile Strength: Ultimate (UTS)

120 MPa 17 x 103 psi

Tensile Strength: Yield (Proof)

68 MPa 9.8 x 103 psi

Thermal Properties

Brazing Temperature

570 to 600 °C 1060 to 1120 °F

Latent Heat of Fusion

540 J/g

Maximum Temperature: Mechanical

160 °C 330 °F

Melting Completion (Liquidus)

590 °C 1090 °F

Melting Onset (Solidus)

520 °C 970 °F

Specific Heat Capacity

880 J/kg-K 0.21 BTU/lb-°F

Thermal Conductivity

100 W/m-K 61 BTU/h-ft-°F

Thermal Expansion

21 µm/m-K

Electrical Properties

Electrical Conductivity: Equal Volume

26 % IACS

Electrical Conductivity: Equal Weight (Specific)

84 % IACS

Otherwise Unclassified Properties

Base Metal Price

10 % relative

Density

2.8 g/cm3 180 lb/ft3

Embodied Carbon

7.6 kg CO2/kg material

Embodied Energy

140 MJ/kg 61 x 103 BTU/lb

Embodied Water

1040 L/kg 120 gal/lb

Common Calculations

Resilience: Ultimate (Unit Rupture Work)

2.3 MJ/m3

Resilience: Unit (Modulus of Resilience)

31 kJ/m3

Stiffness to Weight: Axial

14 points

Stiffness to Weight: Bending

50 points

Strength to Weight: Axial

12 points

Strength to Weight: Bending

19 points

Thermal Diffusivity

42 mm2/s

Thermal Shock Resistance

5.5 points

Alloy Composition

Among wrought aluminum alloys, the composition of 4145 aluminum is notable for containing comparatively high amounts of silicon (Si) and copper (Cu). Silicon is used to increase strength at the expense of ductility. It also lowers the melting temperature and raises the fluidity of the alloy. Copper is used to improve strength. This comes at the cost of a decrease in corrosion resistance and weldability.

Aluminum (Al) 83 to 87.4
Silicon (Si) 9.3 to 10.7
Copper (Cu) 3.3 to 4.7
Iron (Fe) 0 to 0.8
Zinc (Zn) 0 to 0.2
Manganese (Mn) 0 to 0.15
Chromium (Cr) 0 to 0.15
Magnesium (Mg) 0 to 0.15
Residuals 0 to 0.15

All values are % weight. Ranges represent what is permitted under applicable standards.

Followup Questions

Similar Alloys

Further Reading

AWS A5.8: Specification for Filler Metals for Brazing and Braze Welding

ASM Specialty Handbook: Aluminum and Aluminum Alloys, J. R. Davis (editor), 1993