Usage patterns
転機を迎えるto reach/face a turning point
He reached a turning point in his life at age 40.
〈事〉が転機となるfor an event to become a turning point
That encounter became a turning point in her life.
転機をつかむto seize a turning point (as an opportunity)
He seized the turning point brought on by losing his job.
転機が訪れるfor a turning point to arrive
Quitting his job brought a turning point to his career.