Effect of Volume Fraction and Shape of Sulfide Inclusions on Through-Thickness Ductility and Impact Energy of High-Strenght 4340 Plate Steels. Section I. Part I. Axisymmetric and Plane-strain Tensile Ductility. Part II. Impact Energy and Transition Temperature.

Abstract : For many years it has been a goal of the materials scientist to quantitatively link the microstructures of steels to their gross mechanical properties. Because of the very complex structures of steels this goal has been very difficult to achieve. Yet it is believed that average, or otherwise characteristic, features of microstructure are related to overall mechanical properties in a well-defined and quantitative manner. Suitable models of structure together with the capabilities of computer programs which accurately model elastoplastic behavior offer new hope for predicting gross mechanical properties from a knowledge of microstructure. The approach taken in this paper is to represent the structure of a particular steel by a characteristic microcell. The deformation behavior of the microcell is then investigated with large-strain elastoplastic finite-element analysis and related to overall mechanical properties. Quantitative results for the elongation and microcells containing voids of different volume fractions and shapes have been determined. These include graphic descriptions of the growth of voids and the spread and eventual localization of plastic zones of deformation. Although some problems related to numerical stability of the solutions and detection of localized plastic flow remain, the preliminary results are encouraging. Specific recommendations for future work are made. (Author)