Gary A. Amelio was named executive director of the $109 billion Federal Retirement Thrift Investment Board, Washington. He replaced Roger W. Mehle, who returned to private practice as a lawyer. James B. Petrick, acting executive director, will resume his duties as director of benefits and investments. Mr. Amelio was senior vice president and managing director of the retirement and investment services department of PNC Bank, Pittsburgh. No information was available on his replacement. Executive recruiter Heidrick & Struggles assisted in the search.