Investigation of microstructure characteristics of commercially pure aluminum during equal channel angular extrusion

Microstructural evolution during severe plastic deformation (SPD) has been the subject of intensive investigation in recent years due to the unique physical and mechanical properties of severely deformed materials. Ultrafine-grained (UFG) materials produced using SPD processes have excellent mechanical properties over conventional coarse-grained materials. ECAE can produce materials with ultrafine grains in a relatively homogeneous zone leading to remarkable mechanical and microstructure changes without geometrical changes in the specimen. In this study, the evolution of the microstructure of commercially pure aluminum during equal channel angular extrusion was investigated. The microstructural change of materials subjected to ECAE is dependent on the die angle Φ and the ECAE route. A comparison was made between the evolution of the microstructure for specimens deformed by a 90° (Φ) die and that deformed by a 120° die. The influence of route A and route C on the development of the microstructure in ECAE was investigated. The ECAE process was shown to be very effective to produce UFG materials. Commercially pure aluminum (AA1050) with an initial average grain size of 160 μm was reduced to the micrometer level (4 μm by the 90° die and 12 μm by the 120° die) after two passes. Specimens processed with route A had an elongated and banded structure and those with route C had larger number of equiaxed grains.