to simply put,

pertukaran is a statement
penukaran is a process

so in your case, depends on what purpose you use. is it a statement (pertukaran tajuk) or a process (penukaran tajuk).

i think penukaran is more appropriate since you're changing the tajuk penyelidikan.

pertukaran can only be used like this:

"pertukaran tajuk penyelidikan oleh .... or pertukaran tajuk penyelidikan disebabkan ...."

you're welcome