High Ductility Cast Aluminum Alloys with Reduced Silicon

Aluminum alloys 357 and 356 are widely used “workhorse” alloys for aerospace and commercial application. These alloys combine excellent casting characteristics with moderate strength.  Silicon combines with the magnesium in these alloys to form Mg₂Si which strengthens the alloys. The Si levels exceed what is required for the strengthening mechanisms and excess Si is added to improve fluidity, hot tear resistance and feeding characteristics. Improvements in metal cleanliness and casting techniques over the years suggest the amount of Si can be reduced without significantly effecting casting characteristics. Mechanical properties of lower Si alloys show a significant increase in ductility without a reduction in either tensile or yield strength.