Intelligence – Insight – Ingenuity


Aluminium Casting Alloy LM31

This alloy conforms to BS 1490:1988 LM31. Castings are standardised in the as cast (M) condition and in the precipitation treated (TE) condition.

Chemical Composition

  %   %   %
 Copper  0.1 max  Magnesium  0.5-0.75  Silicon  0.25 max
 Iron  0.5 max  Manganese  0.1 max  Nickel  0.1 max
 Zinc  4.8-5.7  Lead  0.05 max  Tin  0.05 max
 Titanium  0.25  Chromium  0.4-0.6  Aluminium  Remainder
 Others total  0.05 max  Others total  0.15 max    


Mechanical Properties

Castings in the as cast (M) condition must be naturally aged for 3 weeks to determine the mechanical properties.


M Sand Cast

TE Sand Cast

0.2% Proof Stress (N/mm2)



Tensile Strength (N/mm2)



Elongation (%)



Impact resistance Charpy (Nm)



Brinell Hardness



Modulus of Elasticity (x103 N/mm2)



Shear Strength (N/mm2)



Strength at elevated temperatures

In comparison with the other Aluminium casting alloys, the strength of LM31 at elevated temperatures is good.

Physical Properties



Coefficient of Thermal Expansion (per °C @ 20-100°C)


Thermal conductivity (cal/cm2/cm/°C @ 25°C)


Electrical conductivity (% copper standard @ 20°C)


Density (g/cm3)


Freezing range (°C) approx.




LM31 has good machinability characteristics.

Corrosion Resistance

This alloy has very good corrosion resistance.


This alloy is suitable for clear or colour (decorative) anodising.

Heat Treatment

Good Strength and toughness can be produced by natural or artificial ageing after casting. Castings in the as cast (M) condition must be naturally aged for 3 weeks before testing to determine the mechanical properties.

The TE heat treatment condition provides artificial ageing. Using this alloy avoids the risks of distortion and cracking on quenching after solution heat treatment.

Applications and General Notes

LM31 has very good shock resistance and is suitable for shock resisting components. It is used for general engineering castings, particularly large sand casting.

HOW can MRT Castings help you?

I want...

New at MRT

Colosio Logo2

MRT Castings is delighted to announce the purchase of a new PFO250 fully automated, die casting cell, from Italian manufacturer Colosio.  

Read More
Southern 19

Visit us at stand C195 at the Farnborough Internaltional Exhibition & Conference Centre on 5th, 6th & 7th February 2019.

Read More
MRT-FactoryWizz Video

Around 6 months ago, we took a hard look at how we use the data we have available to us at MRT Castings. We looked at everything from data being used by machines, data being created by machines all the way through to where data is being left on the cutting room floor and where data can potentially be corrupted or lost through human error.

Read More