Does titanium or brass have a higher shrink rate when cold? I am trying to take a light apart, it is a titanium shell and a brass insert. Don’t want to heat the titanium and risk a color change to only part of the light.
Metals expand and contract relative to their temperature. How much so corresponds to the materials “thermal coefficient of expansion.” Brass has a thermal coefficient of expansion of slightly more than double that of titanium. Hard to say if the brass would come out if you heated the light up.
I’m sure someone else is better qualified to answer but I think titanium needs to get pretty damn hot to change colour. A flameless heat gun should be a good method.
Snuck in before me Hoop
So, if I understand this correctly… the brass should shrink more when cold than the titanium. So, a hard freeze might help it free up.
Freeze spray on the brass may work. The thermal conductivity of titanium is extremely poor compared to brass also. (so work fast) 
That was my thought… exactly!