This question already has an answer here:
- Why do tuning forks have two prongs? 6 answers
What is the phase difference of the oscillation of a tuning fork?
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
To my knowledge, they're 180 degrees out of phase - since they're both going outwards and inwards at the same time, at any given moment they're travelling in opposite directions, hence a one-eighty phase difference.