Influence of friction in equal channel angular pressing - A study with simulation

Severe Plastic Deformation (SPD) processes like Equal Channel Angular Pressing (ECAP) are currently being widely investigated because of their potential to produce ultra fine-grained microstructures in metals and alloys. Ultra-fine materials exhibit superior mechanical properties such as high strength and ductility. The die for ECAP consists of two channels of equal cross sectional area intersecting at a specified angle that usually varies between 90 and 120 degree. The work-piece undergoes intense plastic deformation within a region in the intersection corner of the two channels. A sound knowledge of the plastic deformation and the load is necessary for understanding the relationships between plastic deformation, grain size and mechanical properties. The friction between the die and the work-piece has great influence on the extrusion pressure and flow in the process. This influence can be studied by Finite Element Modeling. In the present work Finite Element Modeling of ECAP process is carried out using the ABAQUS/Standard software. Channel intersection angle of 105 degree was considered for the study. A cylindrical work-piece of diameter 20 mm and length 105 mm was considered for analysis. Coefficient of friction between the die and billet was varied form 0 to 0.1 in steps of 0.02. The pressure required for deformation v/s the stroke length were obtained and compared with experimental data. The results presented are very useful for understanding the effect of coefficient of friction on extrusion pressure, material flow and strain distribution in the work-piece.