A $2.8 Billion Deal by Alcoa For Alumax
Aluminum Co of America, nation's largest aluminum producer, says it is buying Alumax Inc, No 3 aluminum maker, for $2.8 billion in cash and stock; acquisition would expand capability of Alcoa in aluminum extrusion business as well as providing it with Alumax's low-cost aluminum smelters; merger, if approved, will increase Alcoa's annual revenue to $17 billion from $13 billion, add 100,000 employees and increase estimated annual output of aluminum to nearly four million tons; it will leave Reynolds Metals Co as No 2 domestic producer; merger is not expected to have regulatory problems, because companies are merging different lines of business; graph (M)