Papers by Author: Jean-Jacques Fundenberger

Abstract: This paper reviews some recent results concerning surface integrity of materials processed with two important developing techniques: high speed machining (HSM) – here applied to the difficult case of Ti alloys – and low energy high current pulsed electron beam (LEHCPEB) surface treatment of steels. The effect of the processing parameters on the development of microstructure, texture and residual stresses is detailed for modifications occurring both at the surfaces and sub-surfaces.

Abstract: The local crystallography within shear bands (SB) has been examined in a single crystal of {112}<111> orientation of pure copper deformed at 77K by channel-die compression to strains of about 1. Setting up a system for making high-resolution orientation maps using transmission electron microscopy (TEM) has opened new advantageous circumstances for the analysis of orientation changes within SB. This method with spatial resolution higher than 10nm allows the examination of microstructure images composed of nanoscale subcells forming SB. It has been found that for well-developed shear bands, a crystal lattice rotation about <112> direction tends to dominate and this process is usually accompanied by activation of new slip systems. The present work shows that despite the plane strain deformation mode, the mechanism of lattice rotation within emerging SBs may lead to Goss and Brass texture components.

Abstract: FCC metals with different stacking fault energy (SFE), namely Al, Ag and Cu have been investigated for the evolution of crystallographic texture during ECAE deformation using Route A. Different materials with different SFE result in their characteristic textures. The results have been analysed on the basis of microstructural features and related established concepts on texture evolution in FCC metals.

Abstract: Texture and microstructure were investigated after 1 pass equal channel angular extrusion (ECAE) of a single crystal cube oriented Ni billet. Neutron and X-ray diffraction were used to determine global and local textures, respectively. EBSD and TEM investigations were also carried out in order to study fine scale microstructural features. Substantial variations in texture and microstructure, resulting from different efficiencies in the shearing process, were locally recorded through the billet height. The deformation was heterogeneous on both micro and macro scales.

Abstract: We find that a severely rolled FeCo alloy has anomalous enhancement of the rotated-cube {100}<011> texture component and a decrease of the {111} components after annealing, which is contrast to the recrystallization behaviors reported in traditional BCC metals and alloys. The local texture measurements show that two kinds of grains with obviously different orientations, i.e. {100} and {111}, are heterogeneously distributed in the deformed specimen and the migration of high-angle grain boundaries is observed after annealing in the disordering temperature region.

Abstract: FCC metals with different stacking fault energy (SFE), namely Al, Cu and Ag have been investigated for the evolution of crystallographic texture during ECAE deformation using Route A. Different materials with different SFE result in their characteristic textures. The results have been analysed on the basis of microstructural features and related established concepts on texture evolution in FCC metals during other deformation modes.

Abstract: FCC metals with different stacking fault energy (SFE), namely Al, Cu and Ag have been investigated for the evolution of crystallographic texture during ECAE deformation using Route A. Different materials with different SFE result in their characteristic textures. The results have been analysed on the basis of microstructural features and related established concepts on texture evolution in FCC metals during other deformation modes.

Abstract: Texture and microstructure were investigated after 1 pass equal channel angular extrusion (ECAE) of a single crystal cube oriented Ni billet. Neutron and X-ray diffraction were used to determine global and local textures, respectively. To investigate the fine scale microstructural features EBSD was used. Substantial variations in texture and microstructure resulting from different efficiencies in the shearing process were locally recorded through the billet height.

Abstract: An original approach based on semi-automatic treatment of Kikuchi patterns collected by Transmission Electron Microscopy is used to analyse the a2 an g variant distributions in a quaternary TiAl-based alloy (Ti-48at.%Al-2%Cr-2%Nb), with two lamellar microstructures of different fineness. Statistic data analysis shows that neither g variant orientations nor interface misorientations are randomly distributed within a given grain. The largest deviation from randomness is observed for the coarser microstructure. We also pointed out the presence of g|g subboundaries between same but slightly misoriented variants, as well as the existence of some semicoherent g|g twins accommodated by dislocation lattices. The analysis of the misorientation distributions of g|g and g|a2|g interfaces suggests that a variant selection occurs during growth and coarsening stages of the a ® a2 + g transformation process.