Development of a tube-ECAE process to improve the mechanical properties of a metal tube

ECAE is a process of introducing large plastic shear strain in metal. It can produce materials with ultrafine grains in a relatively homogeneous zone, leading to remarkable mechanical and microstructural changes without geometrical changes in the specimen. In this study, ECAE was applied in a unique process to strengthen the mechanical properties of a tube. This proposed method is termed the tube-ECAE process. In the tube-ECAE process, the thickness of the wall of a circular tube is kept constant while the outer and inner diameters of the tube are reduced. A large amount of strain is applied to the wall of tube, leading to grain refinement in the material. In order to investigate characteristics of microstructural evolution such as the grain size and deformation texture during the process, an EBSD OIM analysis was carried out. The analysis confirms that the tube-ECAE process can very effectively produce a circular tube with ultrafine-grains.