Abstract
Solute nitrogen in steels is substantially a strong austenite former and lowers Ms temperature markedly. This means that austenitic stainless steels can be obtained in Fe-Cr-N ternary alloy without adding expensive alloying elements like nickel. In this investigation, 12 to approximately 23%Cr ferritic stainless steels were selected in order to examine the influence of nitrogen and chromium content on austenite stability and on mechanical properties of Fe-Cr-N ternary alloys produced by nitrogen absorption treatment in solid state. The results obtained are as follows: (1) Nitrogen content of specimens can be controlled within the chemical composition range which gives austenite single phase at 1473 K in the ternary alloys. The structures at room temperature are different depending on the chromium content; martensite or (martensite+austenite) below 20%Cr, metastable austenite between 20%Cr and 23%Cr, stable austenite above 23%Cr in case the steels are rapidly cooled from 1473 K, because austenite partially undergoes an eutectoid transformation (decomposition from austenite to (ferrite+Cr2N)) during air cooling. (2) Metastable austenitic steels fracture in brittle mode due to the formation of lenticular martensite during deformation. (3) Stable austenitic steels with 23%Cr are strengthened to 0.7 GPa in 0.2% proof stress by absorbing about 1% of nitrogen with excellent ductilities (40% in elongation). Such an excellent ductility is probably due to high work-hardening rate.
Original language | English |
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Pages (from-to) | 209-214 |
Number of pages | 6 |
Journal | Materials Science Forum |
Volume | 318 |
DOIs | |
Publication status | Published - 1999 |
Event | Proceedings of the 1998 5th International Conference on High Nitrogen Steels (HNS) - Stockholm, Swed Duration: May 27 1998 → May 28 1998 |
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering