I have recently graduated and I was wondering whether, after submitting my thesis, there are any issues (legal or otherwise) if I publish parts of my thesis as a paper in a journal.
My thesis was not published as book, as was the case in this related question.
Ask your thesis advisor! In most cases, the answer will be, "No. Go for it!"
Schools love for their graduates to have publications.
In some institutions, including the one at which I teach, the institution claims ownership in the intellectual property of student work, but even then, a derivative work that results in a publication is likely to be welcome.
In some (many/all?) PhD programs you have to publish before being able to defend your thesis. Some PhD theses can even be composed of the published papers with some sort introduction/discussion (a colleague in the laboratory where I did my PhD did so). Of course, your PhD supervisor needs to approve it, but otherwise I think you can (and maybe you should) safely publish your results before writing your thesis. As an additional note, it is also OK to publish after you have written your thesis, i.e. there should not be issues with self-plagiarism.
Nobody here can say whether there are issues with your thesis. Perhaps there is something different than usual about it.
The most common situation for students in the U.S. is that you can do what you like with the content of the thesis. You can submit the entire thing as a book, or you can divide it up and use it as several papers. This is not plagiarism, because the thesis is not viewed as "published", even though it may be available from your school's library or from services like ProQuest.
The flip side of this situation is that, when we evaluate someone's vita, we don't count the thesis as a "real" publication. So if you are pursuing an academic career, you probably should publish the results of your thesis elsewhere, to develop your vita.
In Europe, some students have many copies of their thesis professionally printed, and distribute the hard copies. I don't know whether they view this as a formal publication.
One other thing to keep in mind is patent rights; a journal article would count as disclosure and invalidate a patent, whereas a thesis may or may not. Some universities have an IP office, and you should check with them if possible; they might have an ownership claim if they employed you.
