Elastic constants and crystal orientation of individual grains of polycrystalline solids from scanning acoustic microscopy

Abstract

The angular dependence of the surface acoustic wave velocity has been measured on an individual grain of aluminum alloy 2519 using a continuous-wave scanning acoustic microscope equipped with a cylindrical lens. The elastic constants and crystal orientation of the grain have been determined simultaneously using a two step nonlinear least-squares fitting of the data. This is the first time that simultaneous measurements of these properties have been reported using scanning acoustic microscopy. The C11 elastic constant is determined to be (113±5) GPa, C12 is (61±3) GPa, and C44 is (29±2) GPa. These values are within 5% of those reported for pure aluminum. The average Young’s modulus for the grain is calculated from the elastic constants to be (74.5±3.0) GPa and is in agreement with the value 74.4 GPa reported for static load measurements of bulk Al 2519 material. The surface plane orientation of the grain is determined to be (210)±4° and is in agreement with an independent determination using x-ray Laue backreflection measurements.