What's Harder (stiffer) Cast Magnesium or Cast Aluminum 1

Dear Forum Readers,

What is a harder (stiffer) metal that resists flexing. Cast Magnesium or Cast Aluminum? Thank you for your time

Craig DeMaio
cde744@aol.com

 

[lgearhart]

Hello Craig!

Cast magnesiom alloys typically have a Young's mudulus of about 6.4 to 6.5 million psi, while cast aluminum alloys are generally about 10.3 to 10.7 million psi. Therefore the aluminum will be substantially stiffer, for the same size & shape part.

Hope this helps!

Lee

 

[hamid76]

Dear Mr. Craig
Iam with mr. Lee in his opinion, and he gave the right mudulus to compare.


Regards

Eng. Hamid S. Al-Baghdady
Metallurgist
IRAQ- Baghdad

 

[hamid76]

Dear Mr. Craig
These informations and data base will be helpfull


1. Aluminum Alloy; Aluminum Casting Alloy; Metal; Nonferrous Metal

Aluminium 201.0-T6; UNS A02010; AA201.0-T6

Component Wt. %

Ag 0.4 - 1
Al 94
Cu 4 - 5.2
Fe Max 0.15
Mg 0.15 - 0.55
Mn 0.2 - 0.5
Si Max 0.1
Ti 0.15 - 0.35


Physical Properties Metric English Comments


Density 2.8 g/cc 0.101 lb/in³

Mechanical Properties


Hardness, Brinell 135 135 500 kg load, 10 mm ball
Hardness, Knoop 170 170 Estimated from Brinell Hardness.
Hardness, Rockwell A 51 51 Estimated from Brinell Hardness.
Hardness, Rockwell B 82 82 Estimated from Brinell Hardness.
Hardness, Vickers 155 155 Estimated from Brinell Hardness.
Tensile Strength, Ultimate 485 MPa 70300 psi
Tensile Strength, Yield 435 MPa 63100 psi 0.2% offset
Elongation @ break 7 % 7 % in 50 mm
Modulus of Elasticity 71 GPa 10300 ksi In Tension
Poisson's Ratio 0.33 0.33
Charpy Impact 5 - 15 J 3.69 - 11.1 ft-lb V-notch
Machinability 90 % 90 % 0-100 Scale (100=best)
Shear Modulus 23 GPa 3340 ksi
Shear Strength 290 MPa 42100 psi Typical for 201.0 - heat treatment unknown
Compressive Modulus 72.4 GPa 10500 ksi Estimated from tensile modulus

Electrical Properties


Electrical Resistivity 0.0000058 ohm-cm 0.0000058 ohm-cm

Thermal Properties


Heat of Fusion 389 J/g 167 BTU/lb
CTE, linear 20°C 19.3 µm/m-°C 10.7 µin/in-°F 20-100°C
CTE, linear 250°C 24.7 µm/m-°C 13.7 µin/in-°F 20-300°C
Heat Capacity 0.963 J/g-°C 0.23 BTU/lb-°F Typical for cast aluminum
Thermal Conductivity 121 W/m-K 840 BTU-in/hr-ft²-°F
Melting Point 535 °C 995 °F Solidus
Solidus 535 °C 995 °F
Liquidus 649 °C 1200 °F

2. Magnesium Alloy; Metal; Nonferrous Metal

Magnesium Alloys; UNS M10100; SAE J465; Mg

Component Wt. %


Al 9.3 - 10.7
Cu Max 0.1
Mg 90
Mn Min 0.1
Ni Max 0.01
Other (total) Max 0.3
Si Max 0.3
Zn Max 0.3




Material Notes:
Sand Casting Temperature 735-845°C

Click here to view available vendors for this material.

Physical Properties Metric English Comments


Density 1.83 g/cc 0.0661 lb/in³

Mechanical Properties


Hardness, Brinell 53 53 500 kg load, 10 mm ball
Hardness, Vickers 68 68 Estimated from Brinell
Tensile Strength, Ultimate 150 MPa 21800 psi
Tensile Strength, Yield 83 MPa 12000 psi at 0.2% Offset
Elongation @ break 2 % 2 % in 50 mm
Modulus of Elasticity 45 GPa 6530 ksi In Tension
Compressive Yield Strength 83 MPa 12000 psi yield at 0.2% offset
Poisson's Ratio 0.35 0.35 Estimated from similar Mg alloys.
Charpy Impact 0.8 J 0.59 ft-lb V-notch
Fatigue Strength 70 MPa 10200 psi R.R. Moore test; 5E+8 cycles
Machinability 100 % 100 % Relative Rating, 100=Best
Shear Modulus 17 GPa 2470 ksi
Shear Strength 125 MPa 18100 psi

Electrical Properties


Electrical Resistivity 0.000015 ohm-cm 0.000015 ohm-cm

Thermal Properties


Heat of Fusion 372 J/g 160 BTU/lb
CTE, linear 20°C 25 µm/m-°C 13.9 µin/in-°F from 0-100°C (32-212°F)
CTE, linear 250°C 28 µm/m-°C 15.6 µin/in-°F Estimated from similar Mg alloys.
Heat Capacity 1.05 J/g-°C 0.251 BTU/lb-°F
Thermal Conductivity 73 W/m-K 507 BTU-in/hr-ft²-°F
Melting Point 430 °C 806 °F Incipient
Solidus 463 °C 865 °F
Liquidus 595 °C 1100 °F


you most welcome

Regards

Eng. Hamid S. Al-Baghdady
Metallurgist
IRAQ- Baghdad

 

[brad]

One important addition, however:
The original poster was referring to bending, and didn't state whether or not the shapes had to be the same. Everybody above is correct: for the same size, aluminum will better resist flexing (by this I presume you mean bending).
However, for the same MASS, one can achieve a larger relative cross-section for magnesium (as it is lighter), which will result in higher I relative to the aluminum.
For the same cross-section: aluminum.
For the same mass: magnesium.
Brad

 

[metman]

Yes, excellent point bradh but Craig possibly does not know that 'I' stands for moment of inertia which is related to the geometry (cross section).

Also Craig don't confuse hardness with stiffness. Although there is a broad relationship between elemental metal bases, hardness does not typically affect stiffness.