Influence of warm caliber rolling on tensile response and high cycle fatigue behavior of hypereutectoid steel

The effects of severe plastic deformation on the microstructural evolution, tensile and high cycle fatigue properties of warm caliber-rolled hypereutectoid steels were investigated. As the reduction in area, associated with amount of plastic deformation of 0, 38, 57 and 81%, increased in caliber-rolled steels, strain accumulation was observed near interfaces between cementite and ferrite in pearlite structures. Initial pearlite structures were changed to spheroidized cementite and submicron-sized polygonal ferrite by dynamic recrystallization according to the warm caliber rolling process. The initial hypereutectoid steel had a yield strength of 375 MPa, tensile strength of 850 MPa, and elongation of 16.8%. As the rolling strain increased, yield and tensile strength increased dramatically to 1381 and 1604 MPa, respectively. The fracture elongation of the 57% reduction in area (RA) sample decreased to 5.4%. However, it is noteworthy that the total elongation of the 81% RA sample increased slightly to 7.1%. The fatigue limit was also enhanced from 450 MPa for initial hypereutectoid steel to 850 MPa for 81% RA without decreasing the fatigue strength ratio (σfatigue limit/σUTS, 0.53). The 81% RA sample had superior fatigue crack propagation resistance and a high tensile strength–elongation combination compared to that of the initial pearlitic hypereutectoid steel.