A Three-Stage Mechanistic Model for Solidification Cracking During Welding of Steel

A three-stage mechanistic model for solidification cracking during TIG welding of steel is proposed from in situ synchrotron X-ray imaging of solidification cracking and subsequent analysis of fracture surfaces. Stage 1—Nucleation of inter-granular hot cracks: cracks nucleate inter-granularly in sub...

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Bibliographic Details
Published in:Metallurgical and materials transactions. A, Physical metallurgy and materials science Physical metallurgy and materials science, 2018-05, Vol.49 (5), p.1674-1682
Main Authors: Aucott, L., Huang, D., Dong, H. B., Wen, S. W., Marsden, J., Rack, A., Cocks, A. C. F.
Format: Article
Language:English
Subjects:
Casting
Characterization and Evaluation of Materials
Chemistry and Materials Science
Coalescing
Concentration (composition)
Cracking (fracturing)
Cracks
Fracture mechanics
Fracture surfaces
Gas tungsten arc welding
Grain boundaries
Hot cracks
Materials Science
Metallic Materials
Metallurgy
Nanotechnology
Physics
Semisolids
Solidification
Structural Materials
Surfaces and Interfaces
Tearing
Thin Films
Volumetric strain
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Summary:A three-stage mechanistic model for solidification cracking during TIG welding of steel is proposed from in situ synchrotron X-ray imaging of solidification cracking and subsequent analysis of fracture surfaces. Stage 1—Nucleation of inter-granular hot cracks: cracks nucleate inter-granularly in sub-surface where maximum volumetric strain is localized and volume fraction of liquid is less than 0.1; the crack nuclei occur at solute-enriched liquid pockets which remain trapped in increasingly impermeable semi-solid skeleton. Stage 2—Coalescence of cracks via inter-granular fracture: as the applied strain increases, cracks coalesce through inter-granular fracture; the coalescence path is preferential to the direction of the heat source and propagates through the grain boundaries to solidifying dendrites. Stage 3—Propagation through inter-dendritic hot tearing: inter-dendritic hot tearing occurs along the boundaries between solidifying columnar dendrites with higher liquid fraction. It is recommended that future solidification cracking criterion shall be based on the application of multiphase mechanics and fracture mechanics to the failure of semi-solid materials.
ISSN:1073-5623
1543-1940
DOI:10.1007/s11661-018-4529-z