Influences of Strain on the Microstructure and Mechanical Properties of High-Carbon Steel

The effects of strain on the microstructure and mechanical properties of 0.81C-0.22Si-0.31Mn (wt%) high-carbon steel were investigated by thermal simulation, scanning electron microscopy, high-resolution transmission electron microscopy (HRTEM), and an electron backscatter diffractometer (EBSD). It was found that when the steel was deformed at 670 degrees C (a temperature between A(1) and A(r1)), a deformation-induced pearlite transformation and cementite spheroidization occurred. The volume fraction of pearlite and the spheroidization ratio of cementite increased with a strain increase from 20% to 75%. The microstructure mainly consisted of pearlite when the deformation strain exceeded 40%. The aspect ratio was at its maximum (5.3) at 40% strain and decreased to 1.4 at 75% strain. In addition, the strength of the steel decreased and the elongation increased rapidly with the increase in strain from 20% to 60% due to the spheroidization of cementite. However, as the strain further increased to 75%, the strength increased slightly due to the refinement of the ferrite matrix. The comprehensive performance of the investigated steel can be improved by applying a strain between A(1) and A(r1).