Martin Marietta Corp. will continue its transformation into a high-tech conglomerate and get out of the aluminum business by selling most of its aluminum operations to Comalco Ltd., Australia's biggest aluminum producer, and one carbon plant to Atlantic Richfield Co.

The Bethesda-based company announced the plan yesterday and said that it expects to receive $200 million in cash and about $200 million in notes for these and related aluminum operations that the company has been trying to sell recently. The future sale of aluminum inventory and raw materials will generate more than $100 million additionally, the company said.

Martin Marietta is setting up a $365 million reserve for losses on the sale of the aluminum operations, and the one-time charge to earnings probably will be between $9 and $10 a share in the third quarter.

Wall Street analysts reacted favorably to the announcement, which they said just about completes the company's shift to concentration on high-margin aerospace and related high-technology operations. The company's stock jumped 3 5/8 in reaction to yesterday's announcement, closing at 42 3/4.

"This decision enables us to focus our time, talents and financial resources on high-technology areas where we have leadership positions: space, defense, communications and information and data management," said Thomas G. Pownall, Martin Marietta chairman and chief executive officer.

"These are the areas of our future growth," he said. "The cash generated by this action will permit us, in addition, to improve our strong financial position by further reducing long-term debt."

The company said it expects to redeem $15 million of Martin Marietta Aluminum 9 3/8 percent sinking fund debentures due in 1996, using proceeds from the planned sale announced yesterday.

In 1983, the aluminum subsidiary provided $671 million of Martin Marietta's $3.9 billion total sales, showing a loss of about $46 million. The American aluminum industry has been hit hard by low demand and depressed prices.

"This is an extremely positive development for the company since it is now more focused on aerospace and high technology," said Morgan Stanley analyst Robert Kugel. "This has been the company's general direction for the last three or four years, and the consolidation now appears to be largely complete. From the stock market's point of view, the benefit of the company being more focused outweighs the huge write-off they have to take."

Under the terms of a memorandum of understanding with Comalco, Martin Marietta will sell the property, plant, equipment and inventories of its Lewisport, Ky., rolling mill; a recycling plant at Lewisport; a primary aluminum smelter at Goldendale, Wash.; an alumina unloading facility at Portland, Ore.; and other assets.

The agreement signed with Atlantic Richfield provides for sale of a carbon plant at Wilmington, Calif., which Martin Marietta operated as a joint venture with Champlin Petroleum Co.

The company continues to be involved in discussions to sell two remaining aluminum facilities, a smelter at The Dalles, Ore., which has been operating at 50 percent of capacity since June 1, and an alumina refinery on St. Croix in the U.S. Virgin Islands.

Martin Marietta said Comalco, with operations in Australia, New Zealand and Japan, wants access to U.S. markets, the largest for primary and fabricated aluminum products.

Martin Marietta said in August that it reached an agreement with Nippon Kokan KK of Japan to set up a joint fabrication operation. Martin Marietta will receive $45 million in cash from NKK's investment in the joint venture, and the local company will contribute its existing Torrance, Calif., plant to the new partnership.

Analysts disagreed yesterday over whether $400 million is a fair price for the aluminum operations, due to different expectations about the future of the industry and a lack of more detailed information about the transaction.