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Vol.42, No.4, 320 ~ 329, 2004
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| Title |
| Dynamic Deformation Behavior of Ultra-Fine-Grained Low-Carbon Steels Fabricated by Equal Channel Angular Pressing |
| 이한상 Lee Han Sang , 황병철 Hwang Byeong Cheol , 이성학 Lee Seong Hag , 안병두 An Byeong Du , 신동혁 Sin Dong Hyeog , 이창길 Lee Chang Gil |
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| Abstract |
| Dynamic deformation and fracture behavior of ultra-fine-grained low-carbon steels fabricated by equal channel angular pressing (ECAP) was investigated in this study. Dynamic torsional tests were conducted on four steel specimens, two of which were annealed after ECAP, using a torsional Kolsky bar, and then the test data were compared via microstructures, tensile properties, and fracture mode. The ECAP`ed specimen consisted of very he, elongated grains of -0.5 μm in size, which were slightly coarsened and had an equiaxed shape after annealing. The dynamic torsional test results indicated that maximum shear stress decreased, while fracture shear strain increased, with increasing annealing time. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen, and their width was smaller in the ECAP`ed specimen than in the 1-hr annealed specimen, although they were not found in the 24-hr annealed specimen. Ultra-he, equiaxed grains of 0.05-0.3 μm in size were formed inside the adiabatic shear band, and their boundaries had characteristics of high-angle grain boundaries. These phenomena were explained by dynamic recovery and recrystallization due to the highly localized plastic deformation and temperature rise inside the adiabatic shear band. (Received February 11, 2004) |
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| Key Words |
| Dynamic torsional test, Ultra-fine-grained low-carbon steel, Equal channel angular pressing, ECAP, Adiabatic shear band, Annealing |
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