On Tuesday, May 10, 2016 at 11:59:48 AM UTC-4, wrote:

They might also be nickle, like the stuff used for connecting cells
together in battery packs.
Eric

Probably not. Nickle is not hard enough to stand up to the heating. It will anneal to a very soft state, even with the stiffener/vibration damper attached.

It is used for the links you describe because it spot-welds very well, and is a much better conductor than steel, and it also takes stress better than copper.