A scarcity of aluminum has forced North Carolina to suspend an effort to replace old license plates.The Division of Motor Vehicles announced this week that the move will help ensure there is enough material to produce first-time plates. The agency had been replacing all license tags that are at least six years old in line with a mandate signed into law two years ago. But the agency says Corrections Enterprises, which makes the plates at the Correctional Institution for Women in Raleigh, doesn’t have enough aluminum to keep up with increased demand.The agency said it issues 400 to 500 new license plates on a typical day, but it is sending out 10 times as many with replacement plates.