This came up on a multiclassed PC today who has extra attack and the Sorcerer Flame Blade spell. He wanted to cast Flame Blade and then use it with extra attack.
When we told him he couldn't because the Flame Blade attack is a special action, not an attack action and it is a spell attack, not a weapon attack. He was pretty pissed about this and then he argued that he was holding the Flame Blade and therefore could use it as an improvised weapon to get extra attack.
I figure this could work, using strength and no proficiency bonus. I think he would get 3d6+strength on a hit as it does "resemble a weapon" that does 3d6.
When we told him he couldn't because the Flame Blade attack is a special action, not an attack action and it is a spell attack, not a weapon attack. He was pretty pissed about this and then he argued that he was holding the Flame Blade and therefore could use it as an improvised weapon to get extra attack.
I figure this could work, using strength and no proficiency bonus. I think he would get 3d6+strength on a hit as it does "resemble a weapon" that does 3d6.