Materials Science Forum Vols. 495-497

Abstract: The texture evolution during Equal-Channel Angular Pressing (ECAP) of an AlMg1Mn0.14 alloy was investigated. The material was subjected up to eight passes with a 90° die angle using route A. This resulted in an equivalent strain of 9.2. The obtained ECAP textures were compared to conventional simple shear textures. In order to investigate the thermal stability of severely deformed material the samples were annealed at several temperatures. The texture evolution during heat treatments was analysed.

Abstract: The accumulative roll-bonding (ARB) process, invented a few years ago, is a promising mode for introducing severe plastic deformation into industrial practice. The ARB process consists in rolling of the pack of two sheets up to 50 %. Then, the rolled material is sectioned into two halves, stacked and the procedure of roll-bonding is repeated. The orientation distribution of ARB processed Al 98 % up to e ~ 12 is analyzed in the paper. The evolution of crystallographic texture has been discussed in relation with changes of mechanical properties and structure.

Abstract: By severe plastic deformation of metals, an ultra fine grain size can be obtained. In the present study an AA 1050 Aluminium alloy has been severe deformed by Equal channel angular pressing (ECAP). A study on the microstructure and the texture of the samples after ECAP and subsequent heat treatment has been carried out. The specimens after ECAP showed a very fine grain size, a decrease of <100> // ND, and an increase of <111> // ND textures. The {111}<112>, {123}<634>, {110}<001>, {112}<111>, {110}<111>, and {013}<231> texture components were increased in the specimens after the ECAP and subsequent heat-treatment at 400° C for 1 hour. One of the most important properties in sheet metals is formability. The r-value or plastic strain ratio has been used as a parameter that expresses the formability of sheet metals. The change of the plastic strain ratios after the ECAP and subsequent heat-treatment conditions has been investigated and it was found that they were two times higher than those of the initial Al sheets. This could be attributed to the formation above texture components through the ECAP and subsequent heat-treatment.

Abstract: Texture development and grain refinement of interstitial-free (IF) steel as a function of ideal simple shear or torsion was undertaken for up to 8 pressings, Route BC. Dominant texture components evolved after a single pass and remained correspondent for all subsequent passes. End-cycle (4 and 8 pass) orientation distribution functions (ODFs) showed an increased spread of contour levels and the re-appearance of texture components similar to the 0-pass condition. Rotation of torsion components away from their ideal pole figure (PF) orientations increased at mid-cycle and decreased to almost equivalent levels after end-cycle passes. This is attributed to the principle slip directions of BCC structures aligning with the shear direction.

Abstract: The orientation evolution in Copper single crystal during ECAE (in Route C) has been investigated experimentally for 90° die angle by X-ray diffraction and TEM-OIM. It is shown that after the previous three passes of ECAE, orientation evolutes with similar mechanism to the simple shear deformation. The grain subdivision occurs with the appearance of many low angle grain boundaries. After four times extrusions the ED of the samples remains stable, their ND rotates around the ED by about 20°. After five times extrusions the main texture component remains stable.

Abstract: Silver of 3N purity was deformed at room temperature by equal channel angular pressing (ECAP) using three passes of route A. The global and local texture were investigated by neutron diffraction and high-energy synchrotron radiation, respectively. The texture is characterized by typical simple shear components of fcc metals which differently deviate from their ideal positions. Local texture measurements reveal that the intensity and inclination of the texture components with respect to the extrusion direction depend on the distance from the top of the extruded bar and change from pass to pass. Reasons for the texture gradient are discussed. The texture of silver is compared with that of copper having a higher stacking fault energy.

Abstract: Texture analysis and the new X-ray method of Generalized Pole Figures (GPF) were used by the study of texture and substructure inhomogeneity of Ti rods, submitted to Equal-Channel Angular Pressing (ECAP) at 400oC. Local texture features testify about gradual rotation of loading axes by ~15o when crossing the rod’s section. As a result of second pass (route C), the specific ECAP texture weakens and the textureless component intensifies. Observed substructure changes are connected with development of dynamic recovery and dynamic recrystallization.

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: 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: A submicron-grained (SMG) microstructure, with an average grain size of ~0.4 µm was produced by equal channel angular extrusion (ECAE). The SMG microstructure was composed of large dynamic recrystallized grains within a matrix of deformed elongated cells. Samples were annealed for various times at 473 K and then examined using transmission electron microscopy (TEM) and electron back scattered diffraction (EBSD). The results specify that a large recovery takes place during the first annealing times. Moreover, MET investigations show nucleation of grains which orientations are found in the recrystallized texture. The EBSD measurements established that, after 7min30s at 473 K, the microstructure is equiaxed and stable with an average grain size of about 2 µm.