Influence of steel heat treatment on ultrasonic absorption measured by laser ultrasonics

Abstract

Laser ultrasonics is combined with the reverberation technique to measure ultrasound absorption during thermal cycles applied to medium-carbon steel samples. During heating to the austenitic phase, a small Snoek peak is observed around 360 • C at 10 MHz along with a signature of the ferromagnetic to paramagnetic transition near 768 • C. Upon cooling, the behavior of the internal friction is much different from that of heating: reduced high-temperature absorption, delayed phase transition, smaller magnetoelastic contribution and stronger Snoek peak are observed. The austenitizing temperature is found to have primary importance on the internal friction behavior during cooling. These measurements show that ultrasound absorption measurements using laser ultrasonics could serve as a basis for a technique to characterize the microstructure evolution of steel in various temperature ranges.

Microstructural characterisation of thermally degraded 2·25Cr–1Mo steel using ultrasonic measurement and its correlation with mechanical properties

“…The study of the influence of steel heat treatment on ultrasonic absorption measured by laser ultrasonic has also been proposed. 10 The analysis of ultrasonic attenuation and microstructural evolution in a low carbon steel (ASTM-A105), containing 0?21 wt-%C has been reported. 11 Ultrasonic velocity measurements have been successfully used to characterise microstructural changes during hardening and tempering in steels, age hardening in aluminium alloys, and to estimate the grain size in austenitic stainless steels.…”