You may want to check the following somewhat related discussion: https://www.researchgate.net/post/Does_chemical_reaction_occur_between_steel_and_aluminum_molten_If_yes_how_much_is_it_How_can_the_amount_of_reaction_be_reduced
To my opinion you can use the intermediate layer of the colloid graphite between the mold and aluminium melt. I have the similar experience and it is rather effective.