Carlos Sergio da Costa Viana

An EBSD Analysis of the Origins of Ridging in AISI 430 Steel Sheets

In the present work the characterisation of both the microstructure and the microtexture of two ferritic stainless steel sheets - AISI 430 (Fe17% Cr) and AISI 434 (17% Cr, 1% Mo) - known to display different ridging behaviours, was carried out by optical metallography, EBSD and OIM techniques. It was concluded that severe ridging is a consequence of: (a) presence of {111} and {001} colonies of grains alternating throughout the sheet plane; (b) through thickness texture inhomogeneity with layers of {001}<110> oriented large grains of low Rvalues sandwiched between layers of higher R-value textured material.

Micromechanisms Involved in Grain Boundary Engineering

Grain boundary engineering has been applied to different materials in order to increase properties particularly sensitive to intergranular phenomena. This work analyses the micromechanisms that allow the control of the amount of special boundaries which respect coincidence site lattice theory. α-brass, a lead alloy, Inconel 625 and Inconel 600 were submitted to different thermomechanical treatments and were analyzed via electron backscatter diffraction in order to characterize their grain boundaries. The occurrence of thin twins in some crystal directions during the deformation step seems to determine the results obtained as well as strain induced boundary migration.

Evolution of the Recrystallization Texture in an IF Steel

Cold rolling experiments were carried out on an IF steel. The samples were partially and totally recrystallized in a muffle type vertical furnace at 650°C for 30 and 45 seconds, 1, 2, 3 and 5 minutes in order to study the formation of the new recrystallization nuclei and their orientation relationships with the surrounding deformed matrix. Both microstructure and texture were examined by SEM. The texture was analyzed by Electron Back Scatter Diffraction (EBSD) and Orientation Image Microscopy (OIM), and represented via the ODF method. The ODF for each sample was the input in a computer calculation specifically created to show the evolution of the principal orientations during annealing. The calculation showed that the first orientation that was formed was (110) [ ] 0 1 1 , in agreement with the results obtained by others. This work aims at providing another tool to study recrystallization texture by using a computer program specifically created to show the evolution of the principal orientations during the annealing through the subtraction of the spherical harmonic series.

Microstructure of a steel perforated by a metallic jet

Abstract The purpose of this work is to present a metallographic study of a carbon steel bar perforated by the impulsive loading of a metallic jet. The results show that the passage of shock waves through the material has strong effects on its microstructure. The development of intense twinning, shear bands, grain growth, and recrystallization was observed.