Analysis of the Scheme of Nonequal Channel Angular Pressing as Applied to the Formation of Sheet Magnesium in a Cold State

The deformation schematics of rolling, equal channel angular pressing, and nonequal channel angular pressing are evaluated. It is noted that the transformation of a circular-section billet into a rectangular-section one with a small thickness is hampered during rolling. This problem also cannot be solved by the application of equal channel angular pressing. In connection with this fact, it is proposed to apply the schematic of nonequal channel angular pressing to workup the cast structure of magnesium. An experimental procedure based on the cold extrusion of cylinders 42 mm in diameter and 40 mm in height is described. The strip at the outlet was 40 mm wide and 1 mm in thickness. The relative reduction of the billet material determined through the area ratio is 96% at an elongation ratio of 17. Specific pressures at the puncheon in the beginning of extrusion is 1200–1300 MPa, while the extrusion force is 1670–1800 kN. A sheet billet is cut into trial lengths, which were rolled at room temperature into foils 50 and 10 μm in thickness without intermediate annealing. Rolling is performed using a Duo mill with a relative reduction of 12–20% at an average speed of 0.1 m/s. To fabricate the foil 50 μm in thickness, 20 passages are performed with a summary relative reduction of 95%. The results of computer simulation by the finite element method show that a constant degree of deformation is attained at a rather sufficient distance from the front end, which is evaluated at the 50-fold strip thickness. The configuration of the deformation region is determined by the calculation of the strain rate field. Power inputs are evaluated. This complex of computational and experimental works allows one to establish that it is possible to fabricate a thin sheet billet with a plasticity level sufficient for subsequent sheet rolling from cylindrical cast magnesium billet for one operation at room temperature. A sheet billet formed in the proposed process has a high workup level by plastic deformation, which is caused by the forming schematic in the presence of a high level of elongation and shear strains. Despite the high-pressure level that should be applied to form the schematic of the uniform compression, allowing for the absence of necessity of billet heating, power inputs turn out no higher than in conventional treatment processes.