AJ alloys (AJ52 and AJ62) are die castable alloys of magnesium that have good creep resistance at high temperature. They contain magnesium, aluminum, and strontium.
In the names the 'J' refers to Strontium.
Alloy Mg Al% Sr% Mn% AJ62 Balance 6 2 0.34 AJ52 Balance 5 2 0.4AJ52 has higher creep resistance, and AJ62 has better castability. Both are used in the BMW magnesium–aluminum composite engine block.
References
AJ alloys Wikipedia(Text) CC BY-SA