Materials Science Forum Vols. 495-497

Abstract: In the Fe-3%Si alloys, grade Hi-B with AlN and MnS as inhibitors, the Goss grains that abnormally grow have not a size greater than the average size of the primary matrix. In such a heterogeneous microstructure, the size factor is not a required condition for the secondary recrystallization. The abnormal growth onset of the small Goss grains appears to be related to a particular behaviour of their grain boundaries and therefore to the local texture so as the distribution of the inhibitors. The presence and the evolution of textured clusters ensure to the small Goss grains a favourable neighbourhood to grow. In this study, their growth ability is compared with that of the largest grains of the matrix. The modified Monte-Carlo approach, performed in the present study, considers the local environment of each grain, so that the growth rate is dependent of its real spatial position, the matrix heterogeneity is then taken into account.

Abstract: This study has been conducted to analyze the effect of texture and microstructure on the anisotropy of yield strength and Charpy fracture toughness of an X80 line pipe steel. The texture and microstructure were investigated by X-ray diffractometer and electron backscattered diffraction (EBSD). The yield strength and impact energy were measured along 0o (longitudinal), 30o and 90o (transverse) to the rolling direction. It was found that the microstructure of the developed steel consisted of fine acicular and polygonal ferrite with small pearlite and martensite or retained austenite (MA constituents). The major components of textures were {332}<113> and {113}<110> orientations. In order to investigate the effect of both morphological and crystallographic texture on yield strength anisotropy, the prediction of the plastic property was carried out by using a viscoplastic self-consistent (VPSC) polycrystal model. The predicted anisotropy of yield strength with VPSC model assuming ellipsoidal grain shape was in a good agreement with experimental observation. EBSD results showed that the density of {001} cleavage planes of Charpy specimen, 30 degree to rolling direction, was the highest compared with that of other specimens. Therefore, the highest susceptibility to the cleavage fracture, i.e. increased ductile-brittle transition temperature, can be seen in the 30 degree direction.

Abstract: This paper examines an effect of boron (B) on dynamic softening behavior, mechanical properties and microstructures for Nb-Ti added high strength interstitial free (IF) steel. For this purpose, IF steels containing 0ppm B, 5ppm B and 30ppm B were chosen. Continuous cooling compression test was performed to investigate dynamic softening behavior. Mechanical properties and microstructures of pilot hot-rolled IF steel sheet were analyzed by uni-axial tensile test and electron back-scattered diffraction (EBSD). It was found that no-dynamic recrystallization temperature (Tndrx) which can be determined from the relationship between flow stress and temperature is a constant of 955oC for all IF steels. However, an addition of B into IF steels increases work hardening rate at the temperature below Tndrx. It was also verified that B retards phase transformation of austenite into ferrite. EBSD analysis revealed that absence of B induces fine ferrite grain size and many high angle grain boundaries.

Abstract: The non-oriented electrical steels, produced with different processing procedures, base their magnetic property improvement mainly on the increase of the Goss component. This paper relates the anisotropy of magnetic properties to texture, describes the texture evolution in both the Fully-processed and the Semi-processed classes of electrical steels.

Abstract: Computer-based alloy and process development requires integration of models for simulating the evolution of microstructure, microchemistry and crystallographic texture into process models of the thermo-mechanical production of Al sheet. The present paper focuses on recent developments in linking softening modules that simulate the progress of recovery and recrystallisation with the following texture changes to deformation and microchemistry models. The potential of such coupled simulations is illustrated by way of the thermo-mechanical processing of Al-Mg-Mn alloys. In particular, the progress of recrystallisation during coil cooling (“self-annealing”) as well as the texture differences between production on a reversible rolling mill and a high-speed tandem line are explored.

Abstract: Using AA5182 and 5754 aluminum alloys, the role of friction in through-thickness evolution was demonstrated. Aside from the mechanical parameters such as roll gap geometry and coefficient of friction, the significance of the role of Fe solute in the matrix was revealed.

Abstract: In order to improve deep drawability of Al-Mg-Si alloy sheets for automotive body panel by texture control, the effects of Mn addition and warm rolling on recrystallization texture were investigated for rolled and T4 treated sheets and the r-value was related to overall texture through thickness. Recrystallization texture after T4 treatment varied significantly depending on alloy composition and rolling condition. Planar anisotropy of r-value could be predicted relatively exactly from recrystallization texture by the Taylor full constraints model for all specimens. Mn addition led to an increase of average r-value in both cold and warm rolled materials, while warm rolling resulted in a decrease of average r-value in spite of relatively high predicted r-values in the surface layer.

Abstract: Uniaxial compression tests were conducted on Al-3mass%Mg alloy under various temperatures and strain rates. High temperature yielding was observed at the temperatures higher than 623K. Texture examination elucidated that fiber textures are constructed in all the deformation conditions examined in this study. It was found that the kinds and intensities of texture components varied depending on deformation temperature, strain rate and the amount of strain.

Abstract: Sheets of the Al-Mg-Si alloy AA6016 have been prepared with different microstructures by rolling and annealing, followed by heat treatment to the T4 condition. These have been biaxially stretched using the Marciniak driving blank method, and their limit strains measured. Such biaxial stretching limits are very sensitive to inhomogeneity with length scales greater than about half the sheet thickness, and significant factors in that inhomogeneity are the materials grain size and the spatial segregation of texture. In this material, it appears that colonies of cube textured grains have an effect on the limit strains. However, there is significant change of texture during stretching and this texture evolution also needs to be considered. Finite element modelling has been used to evaluate the effects of grain size, clustering of the initial texture and texture evolution on the biaxial stretching limits.

Abstract: 6111 Aluminium Alloy in the hot band state was cold rolled to 80% was then annealed at 450oC, 500oC and 540oC for recrystallization. The hot band was also solution heat treated, cold rolled and annealed to the same temperature to look at the difference in the recrystallization texture and precipitation states. It was found that the samples which were cold rolled and annealed without solution heat treatment gave Goss and P components after annealing. For the samples with solution heat treatment, the 450oC sample has a retained Cu type rolling texture while for the 500oC and 540oC the textures are quite random. The retained rolling texture found in the 450oC sample is due to the fact that it was partially recrystallized as the precipitates prevent complete recrystallization. The difference in the precipitation states during and after annealing of the samples with and without solution heat treatment affects the final recrystallization texture.