Effect of infusion on physical damage and armour penetration

Hey all. I know this can be easily tested in the training dummy, if you have all the weapons with enchantments needed, but will an Infusion in the weapon (i.e. Fire, Ice, Plague, etc) convert all my damage from Physical to Elemental? Will Armour penetration and Physical damage stats become irrelevant? Or will the infusion only reduce the damage a little and add a status ailment, but still has a base physical damage? Thanks!