Ультрамелкозернистая структура, текстура и механические свойства низкоуглеродистой стали, полученной различными методами пластической деформации

Abstract

The paper reports on the investigation of the effect of various methods of plastic deformation on the structure, texture and mechanical properties of low carbon 12GBA steel. It is found that multiple isothermal forging results in formation of equiaxed ultrafine-grained (UFG) structure with a uniform distribution of the second phase, the size of which ranges from 50 to 500 nm. The warm rolling leads to formation of UFG fibrous structure type with presence of carbides sized less than 100 nm. X-ray analysis revealed that both deformation schemes result in formation of two-component (110) [112] and (111) [123] texture. Low carbon steel 12GBA with fibrous UFG structure is characterized by high strength, with satisfactory ductility and toughness values similar to ones in case of the coarse-grained (CG) structure. Equiaxed UFG structure steels possess 2 times higher values of fracture toughness and 1.5 times increased tensile strength by comparison with the CG structured steel. Internal strains relaxation annealing of UFG fibrous structure leads to second phase coagulation retaining the two component texture and insignificant change of mechanical properties. It was shown that UFG fibrous steels retains its high level due to 1.5-2 times increase of crack initiation work. Considerable growth of fracture toughness in equaxed UFG steel takes place due to 7 times increase of crack initiation and propagation work.