In situ synchrotron investigation of degenerate graphite nodule evolution in ductile cast iron

DOI: 10.1016/j.actamat.2021.117367

Authors: T. Wigger (University College London; Research Complex at Harwell) , T. Andriollo (Technical University of Denmark) , C. Xu (Technical University of Denmark) , S. J. Clark (University College London; Argonne National Laboratories) , Z. Gong (University College London; Research Complex at Harwell) , R. C. Atwood (Diamond Light Source) , J. H. Hattel (Technical University of Denmark) , N. S. Tiedje (Technical University of Denmark) , P. D. Lee (University College London; Research Complex at Harwell) , M. A. Azeem (Research Complex at Harwell; University of Leicester)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Acta Materialia , VOL 84

State: Published (Approved)
Published: October 2021
Diamond Proposal Number(s): 22627

Abstract: Ductile cast irons (DCIs) are of increasing importance in the renewable energy and transportation sectors. The distribution and morphology of the graphite nodules, in particular the formation of degenerate features during solidification, dictate the mechanical performance of DCIs. In situ high-speed synchrotron X-ray tomography was used to capture the evolution of graphite nodules during solidification of DCI, including degenerate features and the effect of the carbon concentration field. The degeneration of nodules is observed to increase with re-melting cycles, which is attributed to Mg-loss. The dendritic primary austenite and carbon concentration gradients in the surrounding liquid phase were found to control nodule morphology by locally restricting and promoting growth. A coupled diffusion-mechanical model was developed, confirming the experimentally informed hypothesis that protrusions form through liquation cracking of the austenite shell and subsequent localised growth. These results provide valuable insights into the solidification kinetics of cast irons, supporting the design of advanced alloys.

Journal Keywords: Ductile Cast Iron; degenerate graphite morphology; X-ray computed tomography; Growth kinetics

Diamond Keywords: Alloys

Subject Areas: Materials, Engineering


Instruments: I12-JEEP: Joint Engineering, Environmental and Processing

Added On: 13/10/2021 09:41

Discipline Tags:

Materials Engineering & Processes Materials Science Engineering & Technology Metallurgy

Technical Tags:

Imaging Tomography