Ultrasonic Measurement of the Elastic Properties of Polycrystalline Materials at High and Low Temperatures

Abstract

Young's modulus, the modulus of rigidity, and Poisson's ratio have been determined at temperatures ranging from −195°C to 850°C for several different solids using pulses of longitudinal and transverse ultrasonic vibrations. The x- and y-cut crystals used as transducers were kept at room temperature and the velocities of the two types of waves were measured only over the heated or cooled regions. This was done by taking observations on echoes from different points in those regions. The elastic constants are computed from these data. Several pure metals, 28 different steel alloys, an aluminum alloy, and a specimen of lime glass were tested. The moduli of those steels that are non-magnetic decrease linearly with increasing temperature, while the ones that are magnetic show an increasing rate of decrease of the moduli as the α→γ transformation temperature is reached. Precipitation and agglomeration occurring at elevated temperatures in 24 ST aluminum and in a Cr-Ni steel containing 0.92 percent Be and 0.99 percent Wo (Turbaloy) increase the moduli. Poisson's ratio increases with increasing temperature in all the materials tested with the exception of the specimen of lime glass in which it decreases.