Evolution of Microstructure and Texture during Warm Rolling Of a Duplex Steel

The effect of warm rolling on the evolution of microstructure and texture in a duplex stainless steel (DSS) was investigated. For this purpose, a DSS steel was warm rolled up to 90 pct reduction in thickness at 498 K, 698 K, and 898 K (225 °C, 425 °C, and 625 °C). The microstructure with an alternate arrangement of deformed ferrite and austenite bands was observed after warm rolling; however, the microstructure after 90 pct warm rolling at 498 K and 898 K (225 °C and 625 °C) was more lamellar and uniform as compared to the rather fragmented and inhomogeneous structure observed after 90 pct warm rolling at 698 K (425 °C). The texture of ferrite in warm-rolled DSS was characterized by the presence of the RD (〈011〉//RD) and ND (〈111〉//ND) fibers. However, the texture of ferrite in DSS warm rolled at 698 K (425 °C) was distinctly different having much higher fraction of the RD-fiber components than that of the ND-fiber components. The texture and microstructural differences in ferrite in DSS warm rolled at different temperatures could be explained by the interaction of carbon atoms with dislocations. In contrast, the austenite in DSS warm rolled at different temperatures consistently showed pure metal- or copper-type deformation texture which was attributed to the increase in stacking fault energy at the warm-rolling temperatures. It was concluded that the evolution of microstructure and texture of the two constituent phases in DSS was greatly affected by the temperature of warm rolling, but not significantly by the presence of the other phas

Plastic behavior of prestrained metals: microstructural aspects.

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Strain distribution in copper tensile specimens prestrained in rolling

Abstract Sequences of orthogonal rolling-tension experiments were performed on polycrystalline copper sheets. The effect of strain path change on subsequent yield and flow behavior has been investigated. Optical microscopy and transmission electron microscopy (TEM) were used to clarify the physical mechanisms occurring during the second deformation. The observed increase in yield stress in reloading was related to the change of slip systems corresponding to the glide of dislocations with a Burgers vector, which had not been active during prestrain. The transient observed in the workhardening behavior after the path change corresponds to the appearance of disorganization in the dislocation microstructure. It was shown that no special feature of slip behavior inside the grains can be related to the nonhomogeneous surface deformation observed at the beginning of reloading. Also, the plastic instability of prestrained samples corresponding to the maximum load in tension does not seem to be directly controlled by the developed local substructure. The nonuniform deformation observed in reloading was studied using a simplified macroscopic two-zone model. It takes into account the presence of geometrical defects in the samples and considers the importance of the mechanical behavior. The macroscopic results, concerning the delay of starting deformation in some regions, are explained by the model, which allows formulation of an analytical condition necessary for deformation to spread through the length of the sample before necking takes place