Microstructure Characterization of Textured Materials Considering Extinction Phenomenon
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Microstructure Characterization of Textured Materials Considering Extinction Phenomenon T. Kryshtab1, A. Cadena Arenas1, G. Gómez Gasga1, A. De Ita de la Torre2, A. Kryvko3 1
Instituto Politécnico Nacional-ESFM, Av. IPN, Ed. 9, U.P.A.L.M., 07738, México, D. F. México. 2 Area of Material Science, UAM-Unidad Azcapotzalco, Av. San Pablo #180, 02200, México, D. F., México. 3 Instituto Politécnico Nacional-ESIME Zacatenco, Av. IPN, Ed. 5, U.P.A.L.M., 07360, México, D.F. México. E-mail: [email protected], [email protected]
ABSTRACT Texture is defined by the measured polar figure (PF) obtained from the integrated intensity of diffracted X-rays. The integrated intensity can be affected both by the pole density (PD) and by the phenomenon of extinction that reduces the PD and cannot be avoided. PF does not contain information about grain microstructure, but parameters of the primary and secondary extinction are related to the crystal microstructural features. Recently an original X-ray diffraction method was proposed for correction of PD and separation and determination of the primary and secondary extinction parameters for characterization of textured aluminum samples. This problem was solved using some assumptions. The parameter of the primary extinction can be used for calculation of domain size. The secondary extinction parameter is related to the average domain disorientation angle that depends on dislocation density in domain boundaries. Extinction parameters were used for microstructure evaluation of cold rolled nickel with and without annealing at 600°C. The validity of the proposed assumption for nickel samples was evaluated in terms of the extinction length. The corrected pole density and the parameters of primary and secondary extinction were calculated using the first order reflection for two different wavelengths (Cu and Co) and the second order reflection for one of the used wavelengths. In annealed samples the primary and secondary extinction were presented simultaneously. According to the obtained parameters of extinction the microstructure of textured nickel was evaluated. Keywords: X-ray diffraction; Texture; Extinction; Microstructure. INTRODUCTION Solid state materials, in particular metals, in most cases have a polycrystalline structure composed of a multitude of individual grains. However in a majority of materials these grains are rarely randomly distributed. The grain orientation arises during crystallization from a melt and in a further mechanical and/or thermal treatment processes due to anisotropy of a solid [1]. The importance of texture lies in the fact that it leads to macroscopic anisotropic properties of materials. Conventionally accepted formats to provide quantitative texture data are pole figures (PFs) or orientation distribution functions (ODFs) [2]. Determination of microstructure in annealed perfect grains by the conventional X-ray diffraction (XRD) methods, based on
Mater. Res. Soc. Symp. Proc. Vol. 1275 © Materials Research Society
diffraction peak broadening and the kinemati
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