Your Allies in Alloys for over 50 Years

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2012

Dimensional accuracy and internal structure can assess the quality of a casting. Both will influence strength and performance and characterise its value in terms of service. Foundry practice has learnt that structure control during solidification plays a vital role in the achievement of high integrity castings.

 

In castings the two most important metallurgical features are:-

 

GRAIN REFINEMENT: for the macrostructure

A casting is a compact network of individual grains.  The size, shape and bonding of these grains will determine the mechanical properties and soundness of the casting, so there is a real need to control their formation.

 

SILICON MODIFICATION: for the microstructure

Aluminium alloys containing up to 14% Silicon will solidify naturally into coarse, brittle plates of Silicon in a medium of Aluminium. The mechanical strength and ductility of such a casting will be poor and its use limited.

 

Modification of AISi into a fine, fibrous microstructure brings a marked improvement in properties. Fast cooling will achieve the modified AISi structure, but the presence of Strontium produces a similar effect that exists for several hours under normal foundry conditions. Strontium additions are typically introduced in the form of an aluminium based Master Alloy during melt preparation.

 

Titanium to 10%

 

Strontium to 10%

 

Zirconium to 10%

  

Vanadium to 10%