Fracture toughness of 20MnMoNi55 steel at different temperatures as affected by room-temperature pre-deformation

Abstract Fracture mechanics tests, in addition to complementary mechanical tests, were carried out on 20MnMoNi55 steel, in the 0% pre-strain base-material as-rolled state and in the pre-strained ± 10% states. The results indicate that, in general, the pre-deformation, whether positive or negative, causes an increase in the yield and ultimate tensile strength and a decrease in the elongation to fracture. This indicates that the pre-deformation lowers the ductility of the material used, hence indicating the possibility of corresponding decrease in fracture toughness, as found by the trend of behaviour of the parameters J and CTOD, and also the corresponding increase in the transition temperature Ti.