Is Avatar of flame affect Elemental Expression?

I try to make an dex/int invoker which use fire expression so is the Avatar of flame can turn any elemental expression in to fire damage?

You will still triger Arcing Bolt and Icy Wave mainly, but they'll deal fire damage due to damage conversion from Avatar of Fire. Note that you should find another 25% damage conversion to fire, otherwise you'll lose this unconverted damage.