AUDI'S new A4 will use a revolutionary mix of aluminium and steel, according to reports. The MLB-Evo architecture, as it is called, has been developed over five years, Autocar says. It uses a mix of aluminium, steel, and, ultimately, lightweight composite materials that are joined by rivets, screws and super-strength adhesives. It is reported that the compact executive A4 will use high-strength steels for…