Robert N. Tyson has been appointed senior vice president of Guardian Federal Savings and Loan Association. He was previously vice president of the Guardian Service Corporation and Mortgage Loan Department. Mathew I. Werner and Joyce P. Wolf have been named vice presidents of the association.

Brian C. Middleton has been elected senior vice president for northern region operations of United Virginia Bank. He joined the Richmond operations support department of the bank in 1972, became assistant vice president in 1977 and was transferred to the northern region office in 1978.

Kenneth L. Crovo and G. Lawrence Warren have been named senior vice presidents of First & Merchants National Bank. Crovo is responsible for business development in the western zone of te bank's northern Virginia region, which has headquarters in Leesburg. Warren is in charge of commerical lending for northern Virginia. The bank also announced the appointment of Patricia A. Burton as assistant cashier.

Arthur P. Solomon has been named executive vice president and chief financial officer of the Federal National Mortgage Association. Solomon, who will assume his new post Feb. 1, is currently senior vice president of Seraco Enterprises, the real estate and financial services subsidiary of Sears Roebuck & Co. He will oversee all financing activities of Fannie Mae, which is the nation's largest investor in residential mortgages. Solomon replaces Robert Bennett, who will continue as a consultant to the group.

The board of directors of Union Trust Bancorp has elected Harry B. Blocher Jr. vice president of community banking; Harry B. Gemmell Jr. vice president of business loan and development; Thomas B. Howard Jr. vice president of Union Trust Co., and Joseph L. Lynch vice president of international banking.

Donald F. Fatzie has joined the Washington offices of Smith Barney, Harris Upham & Co. Fatzie goes to his new duties as vice president of the sales division from Dean Witter Reynolds, where he was vice president for the firm's southeast region.

Steve L. Lebling and R. Carl Ohle have been appointed assistant vice presidents of Suburban Trust Bank. William L. Shaw has become assistant treasurer of the bank, and John Harrison has been named assistant data processing officer.