Mechanism of the formation of peripheral coarse grain structure in hot extrusion of Al-4.5Zn-1Mg

Abstract

Microstructural evolution leading to peripheral coarse grain (PCG) structure in hot extruded Al-4.5Zn-1Mg rods is investigated. The extent of dynamic recrystallization (DRX) in the as-extruded product falls not in line with the basis over which the existing mechanisms for interpretation of PCG formation are built. A new mechanism is therefore proposed based on partial DRX during extrusion and nucleation and abnormal growth of statically recrsystallised grains.

Keywords:

• Aluminium
• extrusion
• microstructure
• peripheral coarse grain structure