Acoustic damping characterization and microstructure evolution during high-temperature creep of an austenitic stainless steel

Abstract

We studied the microstructure evolution of an austenitic stainless steel, Type 316L, subjected to tensile creep at 973 K through the monitoring of shear-wave attenuation and velocity using electromagnetic acoustic resonance (EMAR). Contactless transduction based on the Lorentz force mechanism is the key to establishing a monitor for microstructural change in the bulk of metals with high sensitivity. In the short interval, 60 to 70 pct of the creep life, attenuation experiences a peak, independent of the applied stress. A drastic change in dislocation mobility and rearrangement interrupted this novel phenomenon, as is supported by observations using a scanning electron microscope (SEM) and a transmission electron microscope (TEM). The EMAR exhibited the potential for the assessment of damage advance and the prediction of the remaining creep life of metals.

Creep-Induced Microstructural Evolution and Acoustic Characterization in Tempered Martensitic Stainless Steel

“…[23][24][25][26][27][28] The results confirmed that an attenuation coefficient showed a peak at a specific time during the creep life and that the time does not depend on the stress and specimen shape.…”

“…As for 2.25 Cr-1Mo steel, Cr-Mo-V steel, Ni-based superalloy, and stainless steels, [23][24][25][26][27][28] the peak and minimum values of the attenuation and local minimum of the velocity were observed in the creep progression of quite different materials under the different test conditions. Shown in Table III is t/t r , where the attenuation shows the peak and the minimum in these materials.…”

“…[21,46] It has been reported that they cause only negligible change in the attenuation coefficient. [23][24][25][26][27][28] Therefore, only the dislocation damping can explain the observed acoustic response.…”

“…It was clear that the attenuation coefficient with EMAR clearly enabled the detection of the dislocation structure evolution in the fatigue progress of pure copper and low-carbon steel [49][50][51][52] and in the creep progress of a Cr-Mo-V, 2.25 pct Cr-1 pct Mo, Ni-based superalloy and austenite stainless steels. [23][24][25][26][27][28] One expects that the attenuation in a type-403 tempered martensitic steel changes because the dislocation structure changes during the creep. Figure 16 shows the results obtained by the digital image analysis of the TEM micrographs.…”

Temporal Compression by Stimulated Brillouin Scattering of Q-switched Pulse with Fused Quartz Glass

“…Previously, we studied the relationship between the microstructure and ultrasonic properties, especially ultrasonic attenuation, with electromagnetic acoustic resonance (EMAR) [16][17][18] during creep in various metals. [19][20][21][22][23][24][25] EMAR is a contactless resonance method using an electromagnetic acoustic transducer (EMAT) [16][17][18] and developed for the contactless measurement of phase velocity and attenuation. The results confirmed that attenuation coefficient shows a peak at a specific time during the creep life and that time does not depend on stress.…”