Acoustic and X-ray Diffraction Texture Parameters and the Elastic Constants of Low-Carbon Steel before and after Fatigue
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CTURE AND PROPERTIES OF THE DEFORMED STATE
Acoustic and X-ray Diffraction Texture Parameters and the Elastic Constants of Low-Carbon Steel before and after Fatigue Tests V. N. Serebryanyia, *, V. V. Mishakinb, and A. V. Goncharb a
Baikov Institute of Metallurgy and Materials Science, Russian Academy of Sciences, Moscow, 119334 Russia Institute of Engineering Science Problems, Branch of the Institute of Applied Physics, Russian Academy of Sciences, Nizhny Novgorod, 603024 Russia *e-mail: [email protected]
b
Received September 30, 2019; revised September 30, 2019; accepted October 23, 2019
Abstract—The texture and the elastic constants of polycrystalline 15YuTA steel are determined before and after fatigue tests. The elastic constants are obtained in terms of the Sayers model in the Hill approximation from the condition of equality of the acoustic and X-ray diffraction coefficients of an orientation distribution function (W400 , W420 ). As a result of high-cycle fatigue tests, the elastic constants of the steel are found to decrease due to a decrease in its density because of loosening. Keywords: texture, elastic constants, bulk longitudinal and shear ultrasonic waves, fatigue tests, 15YuTA steel DOI: 10.1134/S0036029520100225
INTRODUCTION During high-cycle fatigue tests, microdiscontinuities (micropores, microcracks, etc.) form in polycrystalline materials and their dislocation structure and crystallographic texture change. All these structural changes affect the elastic constants of the material and the following related acoustic characteristics: the velocity and the attenuation of ultrasonic waves (UWs) and acoustic anisotropy [1–4]. In the Sayers model [5, 6], a quantitative relation was found between orientation distribution function (ODF) coefficients and the elastic constants and the velocities of bulk UWs for materials with a cubic lattice symmetry and in the case of orthorhombic symmetry of a sample. Texture parameters and the elastic characteristics of a material change simultaneously during fatigue tests. Using only acoustic measurements, one cannot determine these changes separately. Quantitative information about texture in the form of ODF coefficients can also be obtained using the mathematical methods of ODF reconstruction from pole figures experimentally measured X-ray and neutron diffraction methods [7, 8]. Such combined quantitative studies of texture by acoustic, X-ray diffraction, or neutron diffraction methods [9–15] open up fresh possibilities for analyzing changes in both the texture and the elastic properties of materials in various deformation processes.
The purpose of this work is to study the changes in the texture and elastic properties of low-carbon steel sheet during high-cycle fatigue deformation using X-ray diffraction quantitative texture analysis and bulk UWs. EXPERIMENTAL Hot-rolled steel 15YuTA sheets of the following chemical composition were studied (wt %): 0.09– 0.15 C; 0.5–0.8 Si; 0.8–0.12 Mn; no more than 0.3 Cr, Ni, and Cu each; no more than 1.5 Al and Ti each; and
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