Microstructural and ultrasonic characterization of 2101 lean duplex stainless steel welded joint

- Effect of multiple welding pass on microstructure and mechanical properties of LDSS welds is studied.
- Ultrasonic measurement is used to characterize the effect microstructure on the attenuation coefficient of ultrasonic longitudinal waves.
- High microhardness values are found in welding regions with intergranular austenite.
- Ultrasonic c-scan images exhibit a good correlation with microhardness maps and both images resemble the macrograph of the weld.

In this paper, welded joint of a 2101 lean duplex stainless steel (DSS) was studied using ultrasonic attenuation measurements. Two plates were welded using gas metal arc welding (GMAW) process. Attenuation measurements were performed by the immersion ultrasonic pulse-echo technique using a high precision x, y, z scanner in order to generate c-scan images of the welded sample. Experimental measurements show that the longitudinal ultrasonic wave amplitude is significantly affected by the recrystallization of the microstructure caused by multi-pass welding.An increase in the attenuation coefficient of the ultrasonic wave was measured and related to coarser ferrite grains with bigger mean free ferrite distance while recrystallized zones with finer grains of intergranular austenite produce a substantial reduction in the attenuation coefficient. Similarly, it was found from Vickers microhardness maps, that finer microstructure show higher microhardness values while coarser grains present the lower values. The experimental evidence indicates that attenuation measurements can be used as nondestructive evaluation method to assess the microstructure of this type of welds.

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