Brad Pitt is said to have become “volatile when riled” on the set of his ‘Legends of the Fall’ film. The 60-year-old ‘Fight Club’ actor starred in the Western in 1994 and its director Ed Zwick, 71, has now opened up about what it was like to direct the star – revealing one of their bust-ups ended with a chair being flung. He says in his ‘Hits, Flops, and Other Illusions: My Fortysomething Years in Hollywood’ memoir: “It fell to (producer) Marshall (Herskovitz) to talk Brad off the ledge. “It was the first augury of the deeper springs of emotion roiling inside Brad. He seems easy going at first…