Why doesn't aluminium fuse directly to copper? What determines the kinds of metals that can be fused or amalgamated among each other? askscience

Hey there kind scholars!

My girlfriend and I have a strange habit of watching old episodes of that Discovery channel show, "How it's made", to relax and sleep. Last night we watched one episode on "Thermal machines" (such as air conditioning units and refrigerators). On a certain moment during the fabrication of the air conditioner, the narrator said that a certain piece of the aluminium "net" component had to be welded to copper using a zinc-aluminium alloy.

The question(s) then is (are):

Why can't the copper and aluminium be welded directly?

What characteristic on a metal determines it to be able to be welded or amalgamated to another?

Edit 1: a comma.

Submitted January 30, 2018 at 07:23AM by lewdlou http://ift.tt/2DKc4hn askscience