ECAP으로 제조된 초미세립 2상 조직강의 동적 변형거동

Abstract

Dynamic deformation behavior of an ultra-fine-grained dual phase steel fabricated by equal channel angular pressing (ECAP) was investigated and compared with that of an ECAP`ed ultra-fine-grained conventional low-carbon steel. Tensile and dynamic torsional tests were conducted on these two steels, and the deformed microstructures were observed to investigate the deformation behavior under dynamic loading. The ECAP`ed conventional steel consisted of very fine, elongated ferrite-pearlite grains of ~0.5 μm in size, and the ECAP`ed dual phase steel specimen consisted of ferrite-martensite grains of ~1 μm in size. The dynamic torsional test results indicated that maximum shear stress of the dual phase steel was lower than that of the conventional steel, but that fracture shear strain was higher in the dual phase steel. Some adiabatic shear bands were observed at the gage center of the dynamically deformed torsional specimen of the conventional steel, although they were not found in the dual phase steel. These results suggested that the ECAP`ed ultra-fine-grained dual phase steel could be a good way to increase the fracture resistance under dynamic loading as the formation of adiabatic shear bands was reduced or prevented.