Mechanical Behavior Characterization of a Stainless Steel Dissimilar Metal Weld Interface : In-situ Micro-Tensile Testing on Carburized Martensite and Austenite

• Published in: Experimental mechanics 2020, Vol.60 (8), p.1037-1053
• Main Authors: Ben Salem, G., Héripré, E., Bompard, P., Chapuliot, S., Blouin, A., Jacquemoud, C.
• Format: Article
• Language: English
• Subjects: Austenite; Austenitic stainless steels; Biomedical Engineering and Bioengineering; Carburizing; Characterization and Evaluation of Materials; Control; Diameters; Digital imaging; Dissimilar materials; Dissimilar metals; Dynamical Systems; Engineering; Engineering Sciences; Ferritic stainless steels; Ion beams; Laser beam welding; Lasers; Low alloy steels; Martensite; Materials and structures in mechanics; Mechanical properties; Mechanics; Nanoindentation; Optical Devices; Optics; Photonics; Plastic properties; Platinum; Research Paper; Solid Mechanics; Stainless steel; Tensile tests; True strain; Vibration; Welded joints
• ISSN: 0014-4851; 1741-2765
• DOI: 10.1007/s11340-020-00633-1

Background Stainless Steel Dissimilar Metal Welds (SS DMW) between low-alloy steel 18MND5 and austenitic 316L stainless steel are critical junctions in the currently operating reactors because of their heterogeneous microstructure and mechanical properties. The presence of a narrow hard layer of carburized martensite and austenite in the ferritic-austenitic interface creates an important hardness gradient which affects the crack behavior of the SS DMW. Objective In order to evaluate the plastic properties of this hard layer, a micro tensile testing method was developed. Methods Tensile specimens of 15 x 80 x 6 μ m were extracted from the martensitic and carburized austenitic layers by focused ion beam (FIB) micro-processing and tested using an in-situ tensile testing device. A platinum FIB deposition was used to measure local strain in the specimen during the test through digital image correlation (DIC). Isotropic elasto-plastic constitutive laws for the martensite and carburized austenite were obtained from the true strain-stress curves calculated from the micro-tensile tests. Results It was found that the corresponding plastic properties were in a good agreement with nanoindentation measurements and with values obtained from macroscopic tensile tests on crossweld specimens machined perpendicularly to the ferritic-austenitic interface and characterized using laser beam local diameter measurements. Conclusions In-situ tensile testing is a promising technique for plastic behavior characterization of small scale materials and local hard layers in dissimilar metal welds.