SYMPOSIA PAPER Published: 01 January 2000

On the Formation of α-Ferrite in Stainless Steel Alloys


Results of investigations on the microstructure of nickel-containing and of manganese-containing stainless steel alloys by means of the electrical resistivity are reported. These investigations were completed by X-ray diffractometry, by measurements of the magnetic response and of the stored energy. The investigations were performed on AMCR- and 316-type materials and on model stainless steel alloys varying slightly in the composition of the main components of the alloys and the concentrations of the additions.

The following phases were identified: α-ferrite, γ-austenite, α'-martensite, α'def.-martensite, ε-martensite, εdef.-martensite, α-Mn and σ-phase. Small amounts of α-ferrite, α-Mn and σ-phase in stainless steel alloys cause brittleness.

It was found that α-ferrite is always formed when nucleation sites, e.g. α'-martensite and dislocations, are provided, α-ferrite is readily formed by annealing at e.g. 356°C and is dissolved again after annealing for one month at the same temperature, when the nucleation sites are dissolved or recovered.

During irradiation with high energy particles α-ferrite is formed below about 600°C in AMCR- and 316-type stainless steel alloys. The amount of α-ferrite formed at 100°C is so large that many of the stainless steel specimens broke before a dose of 0.11 dpa was obtained.

These findings require a modification of the phase diagrams of stainless steel alloys.

Author Information

Schüle, W
Institut für Angewandte Physik der Johann Wolfgang Goethe-Universität Frankfurt, Leggiuno, Va, Italy
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Developed by Committee: E10
Pages: 894–918
DOI: 10.1520/STP12440S
ISBN-EB: 978-0-8031-5419-3
ISBN-13: 978-0-8031-2852-1