Bimetalic domes

That's why they vary the ratio of the two metals when they design the things. They don't make something, then half ass it till it almost works.

One can play with spring loads and lengths such that this effect can be controlled to some degree. It has the advantage over the OP's approach of grinding material off the disc in that it is reversible.

--Messed around with these ages ago. The delta-T for the flip is inversely proportional to the radius of curvature; i.e. greater radius translates to smaller temp changes to make it flip. I was working on what I call a 'kinetic solar cell' which works very well in theory...