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Using a novel laser ultrasonics technique in situ measurements of austenite grain growth were conducted during continuous heating (10 °C s−1) and subsequent isothermal holding at various temperatures in the range 950–1250 °C in a microalloyed linepipe steel. Based on the experimental results, a grain growth model was developed, which includes the pinning effect of precipitates present in the steel. Analyzing the grain growth behaviour and using the advanced thermo-kinetic software MatCalc, an approach was developed to estimate the initial distribution of precipitates in the as-received material and their dissolution kinetics. The evolution of the volume fractions and mean particle sizes of NbC and TiN leads to a time-dependent pinning pressure that is coupled with the proposed grain growth model to successfully describe the observed kinetics of austenite grain growth. The predictive capabilities of the model are illustrated by its application to independent grain growth data for rapid heat treatment cycles that are typical of the weld heat affected zone.

The ferrite-austenite transformations in A36 and in IF steels were monitored using laser-ultrasonics. Sudden variations of ultrasonic attenuation were observed at transformation temperatures. Dilatometry and standard metallographic observations support an interpretation of these attenuation variations in terms of nucleation and growth of the new phase. Laser-ultrasonics is a new technique to monitor microstructural changes that take place during phase transformations. This information is obtained in real-time and may greatly facilitate laboratory studies on phase transformations. Using ultrasonic scattering models, and with reliable values of the austenite elastic constants as a function of temperature, laser-ultrasonics could provide a quantitative evaluation of grain sizes during phase transformations.

The ultrasound velocity in the sinter-forged YBa2Cu3O7 − δ superconductor was measured and the results showed evident anomalies as well as anisotropies. Both longitudinal and shear wave velocity along the c axis (the forging axis) showed a distinct thermal hysteresis from 65 K to 260 K. The velocity change ΔV V from room temperature to 4 K was 1.5%. The sound velocity along the “basal plane” reached a maximum around 160 K. No distinct thermal hysteresis was observed. ΔV V from room temperature to 4 K was 1%. All of these velocities were measured while sweeping the magnetic field up to 9 T at fixed temperatures of 4 K and 86 K respectively. No velocity change was observed. The shear wave velocity behaved similarly at 9 T during the thermal cycling between room temperature and 4 K.