Transitions between type A flake, type D flake, and coral graphite eutectic structures in cast irons

Journal Article · Sun Sep 01 04:00:00 EDT 1996 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/BF02652368· OSTI ID:382524

Park, J S ^[1]; Verhoeven, J D ^[1]

---

1. Iowa State Univ., Ames, IA (United States). Dept. of Materials Science and Engineering

Directional solidification experiments were used to measure the transition velocities between the type A and coral eutectic structures in high-purity cast irons and between the type A and type D eutectic structures in S and Te doped cast irons. Introduction of O into the gas atmosphere was found to have little effect on the A {R_arrow} D transition velocities in S doped alloys, but it produced a strong reduction in the A {R_arrow} coral transition velocities in high-purity irons. Transmission electron microscopy revealed interesting variations in the defect structures of the graphite in the flake irons vs the type of flake (A or D) and the type of doping element. Scanning Auger microscopy demonstrated that both S and Te segregate to the iron/graphite interface. In the S doped alloys, type A flakes are generally covered with a monolayer of S with patches of O in the form of iron oxide having a thickness on the order of 2 nm. A series of experiments, including examination of fracture surfaces at the quenched solid/liquid growth front, have shown that S segregates to the iron/graphite interfaces from the liquid at the growth front, but O forms at these interfaces during the cooldown. These results are discussed in relation to current models of eutectic growth in cast irons.

• Sponsoring Organization: USDOE
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 382524
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Journal Name: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science Journal Issue: 9 Vol. 27; ISSN 1073-5623; ISSN MMTAEB
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
AUGER ELECTRON SPECTROSCOPY
CAST IRON
DEFECTS
EUTECTICS
GRAPHITE
HYDROGEN ADDITIONS
INTERFACES
KINETICS
LIQUID METALS
MORPHOLOGY
OXYGEN ADDITIONS
SEGREGATION
SOLIDIFICATION
SULFUR ADDITIONS
TELLURIUM ADDITIONS
TRANSMISSION ELECTRON MICROSCOPY