Rolled aluminum is fed into a machine on the auto treatment line at the Alcoa Inc. Davenport Works aluminum facility in Riverdale, Iowa. Check out the companies making headlines in midday trading. Alcoa — Shares of the aluminum stock slipped 5% after the company said executive vice president William Oplinger would succeed Roy Harvey as chief executive and president. Oplinger also joined Alcoa's board of directors, the company added. Nio — The Chinese electric vehicle company's U.S.-traded shares dipped about 1%. The stock pared earlier losses, incurred after the firm denied media reports that the Nio is considering raising as...