is there a way to stop mac osx disk encryption in progress?

Yes, in 10.9+ you can roll it back while its busy encrypting

diskutil cs revert /Volumes/title_drive -passphrase

You will then be promted with the OS X password unlock/decrypt dialog. After that it starts decrypting. The title_drive you can look up with diskutil list or ls -al /Volumes

Check the status with

diskutil cs list

Look for "Conversion Progress" and check if "Conversion Direction:" is set to "backward"