Equal Channel Angular Pressing Of 20MnSi Steel And Its Microstructure And Mechanical Properties

Equal channel angular pressing (ECAP) is a specific processing method in fabricating materials with high properties. ECAP is successfully applied in the production of bulk submicrometer grain materials(SGM).ECAP(route C) of 20MnSi steel was successfully carried out at room temperature in this study. A total equivalent true strain of ~4 was obtained after 4 passes of ECAP. Cold rolling with the same equivalent true strain of 1 and 2 passes of ECAP was carried out. The microstructure evolutions were analyzed by means of optical microscope and transmission electron microscope , and the effects of the passes and annealing temperature on the microstructure and mechanical properties were investigated.The equiaxed submicrometer grains with high-angle boundaries were formed and the average grain size was ~0.2um after the fourth pass. The ultrafine was most significant after the first pass, then the angle of orientation enlarged and grains with high-angle boundaries increased in the subsequent passes. The cementite in the pearlite was deformed into the wave morphology by ECAP, most of which were not broken after the fourth pass, so they had the great ability of plastic deformation. The strength was enhanced with the pass, but reduced after the fourth pass. The ultimate tensile strength(UTS) was ~855MPa with a reasonably high elongation ~16.8 % at the same time. In this paper, the submicrometer ferrite microstructure processed by ECAP was in-situ recrystallization(continuous recrystallization) while those by cold rolling was only in the recrystallization as we usually said during annealing. The cementite in the pearlite by ECAP had stronger ability of spheroidization than that by cold rolling with the same equivalent true strain under the same annealing conditions.