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The solidification behaviors, including the solidification cracking and solidification mode of the Fe-Mn-Cr-Ni-Si alloys at the weld bead during tungsten inert gas (TIG) melt-run welding, were examined by time-resolved in-situ observations using synchrotron radiation X-ray imaging and X-ray diffraction. The dynamics of initiation and propagation of solidification cracking at the weld bead could be observed at the dendrite scale. For the specimen solidified in the austenite mode at a welding speed of 10 mm/s, solidification cracking with a zigzag interface developed via the coalescence of many small pores at the centerline, where the columnar dendrite tips impinged. Quantitative image analysis indicated that the local tensile strain was highly localized at the centerline, and the critical local tensile strain for the initiation of solidification cracking was approximately 0.04. For the specimen solidifying in the ferrite-austenite mode at the welding speed of 10 mm/s, the centerline solidification cracking was suppressed by the formation of many equiaxed γ-Fe dendrites ahead of the growing columnar δ-Fe dendrites. Grain refinement at the centerline can be achieved at a welding speed of more than 7 mm/s without requiring inoculants.

Rights:

• Creative Commons BY-NC-ND Attribution-NonCommercial-NoDerivs 4.0 International
  

Keyword: In-situ observation, TIG melt-run welding, synchrotron radiation X-ray

Date published: 2024-06-20

Publisher: Elsevier

Journal:

• MATERIALS CHARACTERIZATION (ISSN: 10445803) vol. 214

Funding:

Manuscript type: Author's version (Accepted manuscript)

MDR DOI: https://doi.org/10.48505/nims.4567

First published URL: https://doi.org/10.1016/j.matchar.2024.114093

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Updated at: 2024-07-02 09:19:23 +0900

Published on MDR: 2026-06-22 08:26:37 +0900