Mayr, aged 47, was previously president of Novelis Europe, the European arm of giant U.S. aluminium group Novelis and joined Wieland in January this year, Wieland said.
Kroener has been a member of the Wieland executive board since 1988.
Non-listed Wieland sells around 440,000 tonnes of copper products a year with annual sales of around 2.7 billion euros and has major operations in areas including Europe, North America and Asia.
(Reporting by Michael Hogan, editing by Louise Heavens)