Walter W. Williams has been appointed chairman of the board and president of General Electric Information Services Co. in Rockville. He succeeds Gregory J. Liemandt who is leaving General Electric to become chairman and chief executive of the Wyly Corp. in Dallas. Williams joined General Electric in 1956 and was named in 1979 to his present position of vice president and general manager of the housewares and audio business division.

James E. Munson has been elected vice president of the Tiber Construction Co. in Washington. Lawrence A. Duke has been named corporate secretary.

Stanley Ebner has been appointed senior vice president of government relations of the Northrop Corp. He was formerly vice president and manager of the company's Washington office.

Roman J. Barnes has been named vice president for finance of Hekimian Laboratories Inc. in Gaithersburg.

John E. Heaney has been elected vice president for corporate communications of Fairchild Industries Inc. in Germantown. He was formerly in public relations positions with Conoco Inc., General Dynamics Corp. and Rockwell International. Dana J. Lockhart has been named president of Fairchild Credit Corp. a wholly owned subsidiary of Fairchild Industries. Lockhart was formerly a vice president of LFC Credit Corp., a subsidiary of Lockheed Finance Corp.

F. Peter Boer has been elected a corporate vice president of W.R. Grace & Co. of New York and president of the company's research division in Columbia.

Stephen M. Smith has been named general manager for planning and development of Crown Central Petroleum Corp.'s petroleum products division