Papers by Author: Carlos Sergio da Costa Viana

Abstract: 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.

Abstract: 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.