Search

Phase transformations, morphology, and crystallographic texture evolution in hot and cold-rolled Ti-25.51 wt.% Nb alloys are investigated. The experimental procedure involves synthesis of the alloy by arc melting followed by cold or hot rolling with intermediate prior and postheat treatments. Composition and phase analysis of all alloys are conducted using x-ray diffraction techniques and microstructural observations are conducted using an optical microscope. These examinations reveal that the as-melted alloy possesses large millimeter size grains with no stored strain energy and a two phase β − α′ microstructure. Direct cold rolling followed by a short homogenization leads to a β − α′′ mixture with ω precipitates. Two hour annealing before cold rolling leads to an α′ − α′′ mixture with a characteristic triangular martensitic microstructure evidencing the act of shear on formation of the phase. Hot rolling followed by a water quench results in a β − α′′ mixture, while annealing prior to hot rolling transforms the arc-melted material to a α′ − α′′ mixture. The crystallographic textures of similar microstructure mixtures in hot and cold-rolled samples are distinctively different. The analysis shows that the microstructure serves as an identifying characteristic of the processing paths and is highly dependent on the mode of processing. [ABSTRACT FROM AUTHOR]

The effects of process parameters on micro-texture evolution of Al alloy 7075 in machining under extreme conditions were investigated. For the first time, the process parameters in machining are related to the micro-texture evolution below the machined surface, through a computational modeling framework verified by robust experimentation. Finite element analyses (FEA) were performed to obtain the mechanical loads that the material experiences due to chip removal. The viscoplastic self-consistent (VPSC) approach was used to follow the evolution in texture due to the applied loads. The most outstanding texture component, which was seen in the case of increased feed rate, is closely followed by the texture evolution model. The observed discrepancy in experimental and computational results of texture evolution in a few studied cases is believed to be due to the activation of other microstructural evolution phenomena rather than dislocation slip, as a result of the ultra-high levels of exerted strain and strain rates to the machined surface. [ABSTRACT FROM AUTHOR]

The evolution of micro-texture below the machined surface is computationally modeled and experimentally verified. The orientation distribution functions of the grains below the surface were represented in spectral form. The microstructure descriptor coefficients were derived, and their change with respect to the change in the cutting feed rate was computationally calculated and monitored. Micro-texture experimental observations conducted by electron back-scatter diffraction technique verify the modeling outputs. Continuation of changing the process parameter was done by finite element method, and the evolution in texture was investigated by computational modeling. The process path function which correlates micro-texture evolution and cutting feed rate, was obtained by applying the principle of orientation conservation in the Euler space. As a result of the major finding of this work, i.e., derivation of process path functions, the evolution of texture as a function of the material feed rate is numerically determined without any need to texture modeling or finite element analyses. [ABSTRACT FROM AUTHOR]

Titanium alloy Ti-3Al-2.5V is cheaper to produce and has the potential of improved ductility and formability compared to the Ti-6Al-4V alloy. Various heat treatments were performed on cylindrical tensile test bars in order to optimize the mechanical properties of Ti-3Al-2.5V. The tensile properties of heat-treated Ti-3Al-2.5V were determined at four annealing temperatures with different quenching methods and five different solution treatments and five different aging treatments for varying hours. The samples were tensile tested. The results indicated that optimum properties of high strength and ductility were reached at 926 °C of solution treatment and 480 °C of aging. [ABSTRACT FROM AUTHOR]

Abstract: A processing path model proposed earlier by Bunge is used for the prediction and optimization of texture in polycrystalline hexagonal materials. The model relies on a principal of conservation in the orientation space and the existence of a texture evolution parameter. The numerical simulations from a well-established crystal plasticity model produced the initial data for the calculation of the processing path parameters. The model is then capable of predicting the texture evolution starting from other initial textures for any specific deformation path. The simulated results from the processing path model agree well with those from the crystal plasticity model. The family of processing path lines developed based on the present model can be used as a guide to optimize the processing paths that will lead to a microstructure with desired properties. [Copyright &y& Elsevier]

Abstract: Textured Zn–1.1%Al alloy sheet, free of through-thickness texture gradient, has been subjected to superplastic deformation. The texture of the samples are characterized by two 0002 components. During superplastic deformation, their intensity remains quite stable at the surface and decreases significantly in the mid-layer. Such texture changes are explained by the different sliding–rotation behavior of grains at the surface and in the bulk. [Copyright &y& Elsevier]

The effects of high magnetic field annealing on the preferred orientation distribution (texture) and magnetic anisotropy of arc-melted FePd alloy were studied by recalculated pole figure method and vibrating sample magnetometry. A rigorous texture characterization method was used to analyze the crystal orientation distribution of the annealed FePd. As compared with annealing without magnetic field, the high magnetic field annealing increases the volume fraction of crystal grains with c-axis aligned along the annealing magnetic field direction. A corresponding uniaxial magnetic anisotropy was also observed in the magnetically annealed FePd alloy. [Copyright &y& Elsevier]

Magnetic fields are said to influence texture and microstructure evolution of ferrous alloys. The objective of this work is to investigate the effect of a magnetic field applied during secondary annealing on texture evolution and grain size of a nonoriented silicon steel sample. Temper cold rolled silicon steel samples were annealed under the same conditions with and without the magnetic field. The final grain size was the same for both annealing conditions. The application of a magnetic field affected texture development by increasing the strength of the Goss orientation and decreasing the intensity of grains {111} oriented parallel to the normal direction of the sheet. [ABSTRACT FROM AUTHOR]

A general methodology is developed to model the texture evolution of polycrystalline materials during mechanical processing. The methodology is based on the conservation of texture volume as proposed by Bunge. One of the interesting features of the formulation is that the texture coefficients can be predicted for each processing path using a sixth rank tensor. The range of validity for this methodology is investigated using a set of input data predicted by a crystal plasiticity model based on Taylor. [Copyright &y& Elsevier]

Highly textured Zn–1.1%Al sheet was annealed in a direct-current magnetic field of 25.5 MA/m. Depending on the orientation to the field the texture components strengthened, retained their original intensity or disappeared. The results obtained are interpreted in terms of magnetically induced selective grain growth. [Copyright &y& Elsevier]

Abstract: X-ray Peak Profile Analysis was employed to determine the evolution dislocation density and dislocations type in hot rolled commercially pure titanium specimens. It was found that 〈a〉 dislocation type is dominating the deformation mechanism at all rolling reduction levels studied here. A good agreement was found between the texture evolution and changes in dislocation slip system activity during the deformation process. [Copyright &y& Elsevier]

Temper cold rolled silicon steel samples were annealed with and without an applied magnetic field. The final grain size was the same for both annealing conditions. Application of a magnetic field affected texture development by increasing the strength of the Goss component and decreasing the intensity of the gamma fiber. [Copyright &y& Elsevier]