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 90degrees 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 sub-rains 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 similar to0.2 mum. 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 180degrees 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. (C) 2002 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.