Processing of a low-carbon steel by equal-channel angular pressing

A low-carbon steel containing 0.08% C was processed by Equal-Channel Angular Pressing (ECAP) with the sample rotated by 90° in the same direction between each pass in processing route B(C). Samples were pressed through a total of three passes at room temperature. The results reveal an evolution in the microstructure with increasing strain from an array of elongated subgrains separated by boundaries having low angles of misorientation to an array of reasonably equiaxed grains separated by high-angle boundaries. The average grain size after three passes was ∼0.2 μm. Processing by ECAP increases the 0.2% proof stress and the ultimate tensile strength (UTS) but there is a corresponding decrease in the elongation to failure. A comparison with earlier published results obtained using processing routes A (no rotation between passes) and C (rotation of 180° between passes) suggests that route B(C) is preferable because these samples exhibit an extensive region of strain hardening and a reasonably high elongation in tensile testing at room temperature. This difference is attributed to the greater microstructural homogeneity that is achieved when using processing route B(C).