No abstract

No abstract

No abstract

No abstract

No abstract

No abstract

The effect of compressive plastic prestrain on the resistance of carbon steels to microcleavage is investigated using grade 30 steel as an example. Precompression is found to result in the occurrence of anisotropy of the "brittle" strength R mc of the steel, the essence of which is in its decrease for specimens cut out in the longitudinal direction and increase in the microcleavage resistance for specimens cut out in the transverse one. It is shown that the main cause of this effect are oriented residual stresses. The value of the oriented residual stresses for specimens cut out in the longitudinal and transverse direction is estimated. A strong embrittlement of the steel is observed in the longitudinal direction after compression. The shift in the ductile-brittle transition temperature reaches the maximum value of 168°C.Introduction. In the majority of cases, structural alloys are known to be subjected to significant plastic strains resulting in the occurrence of the anisotropy of mechanical properties. At present, the anisotropy of elastic and plastic properties (yield stress, flow stress) of metals and alloys has been studied quite well. The role of the crystallographic texture in the formation of the anisotropy of the above-mentioned properties of a metal is shown in [1]. At the same time, the main factors responsible for the effect of orientation of the applied load on the ability of a textured material to resist brittle fracture remain unclarified. Unfortunately, the unambiguity in selecting the mechanical characteristics for quantitative estimation of this property is absent. In this case, there are often used the reduction of the cross-section area, impact toughness, and crack growth resistance. However, these characteristics can change considerably with the change in the fracture mechanism from ductile to brittle fracture, therefore to determine the contribution to their variation (in fact, the anisotropy) is problematic. Recently, to assess the strength of metals and alloys in a brittle state (the brittle strength), there has been used the ratio of the values of the local stress of brittle fracture at the notch apex σ F obtained in different directions [2,3]. However, the determination of σ F for a highly deformed metal presents significant methodological problems.In [4], the effect of an abrupt decrease of the microcleavage stress in uniaxial tension for a polycrystalline iron prestrained by compression was detected. More systematic studies on the effect of the compressive prestraining on the brittle fracture resistance under conditions of uniaxial tension were performed in [5] where the resistance to cleavage S cl was used as a measure of the ability of a material to resist brittle fracture. It was also shown that for steel 15Kh2MFA, S cl decreases with the increase in the compressive prestraining. As this takes place, the effect of change in the brittle fracture micromechanism from a transcrystalline fracture for the undeformed steel to an intercrystalline one for the steel after compression is obser...

No abstract