Microstructure Characterization of Textured Nickel Using Parameters of Extinction
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Microstructure Characterization of Textured Nickel Using Parameters of Extinction A. Cadena Arenas1, T. Kryshtab1, J. Palacios Gómez1, 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 X ray diffraction (XRD) is the common technique for texture analysis by means of pole figure (PF) measurement. PF reflects the grains orientation distribution but contains no information about grain microstructure. The reflected intensity can be affected by the extinction phenomenon that reduces the pole density (PD). The parameters of extinction are related to the crystal microstructure. The parameter of the primary extinction is connected with domain size and parameter of the secondary extinction is related to the angle of domains disorientation that depends on dislocation density in domain boundary. An original XRD method is proposed for correction of PD, considering extinction phenomenon, and separation of the extinction parameters in the case of textured aluminum. The problem is solved under some assumptions. In the present work cold rolled nickel with and without annealing at 600 °C is investigated. The validity of the proposed assumptions for Ni is evaluated in terms of the extinction length. The corrected PD in the maximum of PF and the parameters of the primary and secondary extinction are calculated using the first order reflection for Cu K - and Co K - radiations and the second order reflection for one of the used wavelengths. Both in cold rolled sample without annealing and in the annealed sample the primary and secondary extinctions are present simultaneously. According to the obtained parameters of extinction the microstructure of textured nickel is evaluated and their modification at the annealing process is demonstrated. Keywords: X-ray diffraction; texture; extinction; microstructure; dislocations INTRODUCTION In polycrystalline materials grain orientations are rarely randomly distributed. The preferred orientations or, more concisely, texture can arise due to anisotropy of a solid [1]. The common quantitative X-ray texture analysis is based on pole figure (PF) measurement by means of X-ray diffraction (XRD) techniques [2]. PF is characterized by pole density (PD) obtained from the reflected intensity of X-rays and does not contain information about microstructure such as size and lattice perfection of crystallites. At PF measurement can take place extinction phenomenon (FP) that reduces PDs, cannot be avoided and must be taken into account [3, 4]. The conventional XRD methods for evaluation of microstructure in polycrystalline materials are based on diffraction peak broadening and the kinematical scattering theory [5]. But they cannot be used in the case
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