Nitrogen wouldn't work in this situation. In fact nitrogen and aluminum will burn, forming AlN. Normally this doesn't happen because of Aluminum readily forms

Nitrogen wouldn't work in this situation. In fact nitrogen and aluminum will burn, forming AlN. Normally this doesn't happen because of Aluminum readily forms a "rust" layer in the presence of oxygen, and there isn't enough heat. Molten aluminum in a pure nitrogen environment wouldn't have that layer, and there likely would be enough heat.