Microstructure and texture evolution of AA 6063 during an Ex-ECAE process

Abstract

Equal channel angular extrusion (ECAE) has been studied at the lab scale for many years. However, few successful industrial applications of the ECAE process have been reported. In the present work, a process referred to as Ex-ECAE that was composed of two processes of the direct extrusion and the ECAE via route C, was developed. The Ex-ECAE process was developed to refine the microstructure of the extrudate, particular the coarse grain layer (CGL) on the surface of the extrudate. The Ex-ECAE die with a die angle of 120° contained three segments and was used in the conventional direct extrusion press. The high friction and the continuous routes of the ECAE resulted in asymmetric dead metal zones (DMZs) to be formed at the corners of the die channel. It revealed that the visible grains in the CGL were refined and became invisible due to the intense shear deformation as the CGL flowed along the boundaries of the asymmetric DMZs. The textures of the Ex-ECAE at the various segments were studied by EBSD. This study demonstrated that the ECAE process could be scaled up using the extrusion press. Success or lack of success depended on the capacity of the extrusion press and the die design.