TEMPERATURE DEPENDENCE OF ACOUSTIC BIREFRINGENCE OF SHEAR ELASTIC WAVES IN POLYCRYSTALLINE ALUMINUM

Abstract

The article presents the results of a study of the temperature dependences of the shear elastic waves velocity of polycrystalline aluminum alloy AD0 in the temperature range from 20 °C to 45 °C. For the studied material the temperature dependence of the acoustic birefringence parameter characterizing the a shear ultrasonic wave splitting into two orthogonally polarized waves propagating at different velocities is determined. The calculation of the acoustic birefringence parameter was carried out according to the data of the propagation time precision measurement of shear elastic waves (the measurement error of the propagation time is 1-2 ns), polarized along and across the direction of rolling. Theoretical studies have shown that for materials with weak anisotropy, the temperature dependence of the acoustic birefringence parameter is mainly related to the influence of temperature on the elastic anisotropy of the crystals that make up the polycrystalline material and the characteristic of the crystallographic texture – the coefficient of the orientation distribution function W420. Corrections to the value of the birefringence parameter with temperature change are given. It was experimentally obtained that the acoustic birefringence parameter increases by 9% with increasing temperature, which must be taken into account by using it as a diagnostic parameter to evaluation changes in the characteristics of static and fatigue strength. An algorithm is proposed for estimating the prediction of the temperature dependence of the acoustic birefringence parameter of a single-phase material when the crystallographic texture changes as a result of plastic deformation, for example. A good coincidence of the predicted temperature dependence of the acoustic birefringence parameter with the experimental one was obtained – the deviation error of the calculated curve from the experimental one was 0.2–2% in the temperature range of 20 °С to 45 °С.