Tube Reversing and Extrusion (TRE) as a Novel Method for Producing UFG Thin Tubes

In the present research, a new severe plastic deformation method has been introduced for producing thin walled tubes with ultrafine grained substructure. The tube reversing and extrusion (TRE) technique was applied to a CP-aluminum and thin walled tubes with ultra-fine grained microstructure were successfully processed. The obtained results from tensile tests at room temperature showed the significant increase in mechanical properties of TRE processed thin walled tubes including yield and ultimate strengths and micro-hardness due to grain refinement. The microstructure evolution and deformation behaviour of commercially pure aluminium under TRE processing was simulated by the constitutive model as a micromechanical approach implemented in the finite element framework. The continuous dynamic recrystallization (the evolution of dislocation density and grain size) of aluminum tubes during TRE was considered as the main grain refinement mechanism in micromechanical constitutive model. Also, the flow stress of material in macroscopic scale was related to microstructure quantities. This was in contrast to the previous approaches in FEM simulations of SPD methods where the microstructure parameters such as grain size were not considered at all. The FEM simulated grain refinement behavior was consistent with the experimentally obtained results.