Papers by Keyword: Plane Strain Compression

Abstract: In previous study, it was investigated texture formation behaviour of high-temperature plane strain compression test at 723K, under a strain rate of 5.0. It was found that the main texture component and it was sharpness vary depending on deformation conditions. To clarify the characteristic of texture formation behaviour, it is necessary to investigate at various deformation condition. Therefore, in this study, is investigating the influence or texture formation behaviour and strain, strain rate at 673K. Three kinds of specimens with different initial textures were machined out from a rolled plate having a <0001> texture. The plane strain compression tests were conducted at a temperature 673K, and a strain rate of 5.0, with strain between-0.4 to-1.0. After compression tests, the specimens were immediately quenched in oil. The texture evolution was conducted by the Schulz reflection method using Cu Kα radiation and EBSD. Before the deformation, {0001} of specimen A was accumulated in the center of pole figure. The {0001} of specimen B was accumulated at the RD direction. The {0001} of specimen C was accumulated TD direction. As a result, work softening is observed in all the cases at the true stress – true strain curve for three types of specimens. After deformation, the maximum pole density of increases with increasing strain. In this study, it was found that the stable orientation was (0001)<100> and (0001)<110> during deformation.

Abstract: The crystallographic aspects of recrystallization twinning have been characterized in {110}<001> and {110}<112>-oriented single crystals of Cu-2%wt.Al and Al-1%wt.Mn alloys. The samples were plane strain compressed to logarithmic strain of 0.52 and then lightly annealed. SEM/EBSD local orientation measurements on partly recrystallized samples demonstrate the appearance of a specific number of new orientation groups of recrystallized grains, which resulted from rotation of the deformed crystal orientations around axes lying near (but rarely at) selected the <111> directions. Then the primary nucleus can transform through the formation of a first generation recrystallization twin. The most frequent situation was that the twinning plane normal was situated near the rotation axis, around which the crystal lattice of the ‘primary nuclei’ rotates. Based on new algorithm to identify coherent and incoherent twin boundaries the influence of free surface on the intensity of annealing twinning was analyzed.

Abstract: Early stages of recrystallization were observed for the Al-Mn-Mg-Zr(Sc) aluminium alloy containing a fine second phase particles. The samples were plane strain compressed to 40%, 60% and 83% and then annealed. The processes of the recovery and the nucleation of new grains were analysed with the use of scanning electron microscopy equipped with a high resolution electron backscattered diffraction facility. The deformed alloy contained a structure of flat grains situated parallel to the compression plane. After annealing, the structure coarsened. However, the growth of the new grains was strongly hindered by the presence of particles, and the elongated shape of the deformed grains was conserved up to the later stages of recrystallization. In the case ofthe samples deformed up to 40%, the structure was transformed by the mechanism of continuous recrystallization, whereas, in the case of the samples deformed up to 60% or 83%, both mechanisms- of continuous and discontinuous recrystallization - were valid. A particular role in the rise of thenuclei and the structure spheroidization is attributed to the thermally activated migration of the low-angle grain boundaries and the movement of the dislocations stored inside the cells. This leads to an increase of the misorientation angles across the pre-existing low-angle boundaries.

Abstract: The behavior of texture formation during high-temperature deformation in AZ80 magnesium alloy is investigated. Three kinds of specimens were machined out from rolled plates. The plane strain compression tests were conducted at various deformation conditions – temperature, strain and strain rate. After compression deformation, texture measurement was carried out on the mid-plane section parallel to the compression direction by the Schulz reflection method and EBSD measurement. The maximum values of the flow stress are observed in all the cases at the true stress – true strain curve for three type of specimens. It is found that the main component of texture and the accumulation of pole density vary depending on deformation condition and initial texture. Six kinds of crystal orientation components have been observed after deformation in total. (0001)<10-10> is formed regardless of the initial texture.

Abstract: The objective of this paper is to identify the predominant crystallographic relations between deformed state and recrystallized grains during the early stages of recrystallization of fcc metals with medium and low stacking fault energy. The experimental investigations, based on SEM/EBSD measurements, have focused on the transformations which occur in plane strain compressed single crystals with stable orientations. After annealing the disorientation across the recrystallization front 'defines' the final rotation by angles in the ranges of 25-35^o and 45-55^o around axes mostly grouped near the <122>, <012>, <112> and <111> directions located around the normals of all four {111} slip planes.

Abstract: A novel experimental investigation of both high and medium stacking fault energy bi-crystals of aluminum and copper, respectively, show that orientation, grain interaction and material are all key factors in the stability of some ideal rolling texture components. Ideal {110} or {112} orientations obtained from high purity aluminum or copper single crystals were embedded within a {110} crystal orientation of the same material and reduced 60 percent by channel die compression at room temperature. Spatial misorientations developed inside the deformation bands were analyzed using SEM-based EBSD. The presence of long-range orientation gradients in some of the crystals revealed the interacting nature of polycrystalline deformation. From the results it is proposed that f.c.c. polycrystalline grains can be classified according to their stability and susceptibility to deformation: (i) stable and interacting; (ii) unstable and interacting; (iii) stable and non-interacting; (iv) unstable and non-interacting.

Abstract: Formation process of textures in AZ80 is investigated on polycrystal specimens with different initial textures by plane strain compression deformation at 673 K and 723 K with strain rates between 5.0×10^-4s^-1 and 5.0×10^-2s^-1. Three kinds of specimens were taken out from the extruded bars with (direction of the extrusion) fiber texture by changing the geometrical relationship with the extrusion direction. In the case of the specimen having parallel to the compression direction before deformation, the initial fiber texture gradually transformed into several orientations with increasing strain at 723K with a strain rate of 5.0×10^-2s^-1. oriented grains, which was not seen in the pole figures before deformation appeared after the deformation up to -1.0 in true strain. The other two kinds of specimens have compression directions perpendicular to direction. The textures after deformation of these two kinds of specimens also consisted of several components. Some of them are common among the three kinds of specimens and the others are retained components of the initial texture.

Abstract: Thermomechanical Controlled Processing (TMCP) including accelerated cooling after the final hot rolling pass is a well-established technology, widely applied in HSLA steel plate production. However, there are still certain limitations, especially for thicker plate. The rolling schedule includes a long holding period (HP) after the roughing stage to allow the temperature to fall sufficiently for optimised TMCP during finishing. Intermediate Forced Cooling (IFC) applied during the HP can increase productivity by decreasing the required hold time, can restrict austenite grain growth, and can also improve the subsequent strain penetration in thick plate with further metallurgical benefits. Multi-pass plane strain compression (PSC) tests have been performed on the thermomechanical compression (TMC) machine at Sheffield University including different severities of IFC. Clearly it is impossible to simulate all aspects of the temperature and strain gradients present in thick plates in laboratory specimens, and most of the tests were conducted at temperatures and strains calculated by Finite Element modelling as relevant to specific positions through the plate thickness. However, some aspects of the gradients were addressed with tests using cold platens. The results have indeed shown that IFC can shorten the HP and reduce austenite grain growth and its variation across thick plate.

Abstract: Magnesium (Mg) is a hexagonal close-packed light metal whose deformation re-sponse is characterized predominantly by easy slip on the f0002g basal plane at temperaturesbelow 200°C. Rolled sheet products develop a strong basal texture and become \plasticallychallenged" in subsequent forming operations. In the literature, additions of rare earth ele-ments (REE) to Mg have inconsistently reported non-basal texture formation. In this work,Mg-0.2wt%Gd and 0.2-wt%La were investigated to determine whether the presence of theseelements contributed to non-basal texture formation after elevated temperature plane straincompression. Test specimens were prepared from book-mould castings after homogenization at400°C, and reduced 50% in a channel die at 250, 325, or 375°C and 10^-2/s. The stress-strainbehaviours were all characterized by apparent twin-related softening, followed by monotonichardening to the end of the imposed deformation. The yield stress for Mg-0.2%La (15-22 MPa)was higher and less temperature dependent than for Mg-0.2%Gd (10-18 MPa). Texture mea-surements indicate the spread of ideal basal texture about TD with increased temperature, butalso also greater non-basal textures in the Mg-0.2%Gd alloy, particularly at 325°C. Electronchanneling contrast imaging revealed a more re ned and homogeneous substructure in the Gd-containing alloy compared with larger microbands in the La-containing alloy, and suggests thatcontinuous recovery and other available slip systems may contribute to these di erences.

Abstract: The mechanical properties and microstructures were investigated for AZ80 Mg alloy during plane strain compression and extrusion processing. The results show the tensile strength increases with the increasing deformation degree in the two-phase zone due to sufficient dynamic recrystallization and work-hardening effect. In single-phase zone, the tensile strength increases firstly and then does not varies basically when the deformation degree is greater than a certain critical value. This is very beneficial to optimize processing parameters to obtain microstructure with improved mechanical behavior.