High-temperature deformation properties of austenitic Fe-Mn alloys
- PDF / 318,873 Bytes
- 11 Pages / 612 x 792 pts (letter) Page_size
- 110 Downloads / 282 Views
solution, Mn has a moderate solid solution hardening effect in Fe. In steels, it also effectively combines with sulfur to form MnS, which has a much higher melting point than FeS and thereby prevents hot shortness. As such, Mn, added to contents typically ,2 wt pct, is ubiquitous in steel as it enables steelmakers to avoid most hot working problems. The use of high Mn contents in steels is more recent: it has been used to develop austenitic Mn steels that combine a moderate strength with an extremely high ductility and toughness, it is an essential element in weldable high-strength structural steels, and it has been used to fully or partially replace Ni in austenitic stainless steels in periods of Ni shortage. The Mn contents, less than 2 wt pct, are present in all structural C-Mn steels. A combination of Mn and about 0.1 pct C results in a high toughness and ductility with high work hardening and usually a good wear resistance. In Hadfield steels, high pct Mn contents, in the range of 7 to 20 pct Mn, are typically combined with 0.6 to 1.2 pct C. Hadfield steels are characterized by a high resistance to both impact and abrasion and a pronounced work hardening. There is currently a strong interest for the use of high Mn alloying contents in special ferrous alloys: it has been used to develop ferrous shape memory alloys and its potential to fully replace Ni in austenitic steels has received much attention. Steels with a Mn content similar to that of Hadfield steel but with a much lower C content (;0.03 pct) are of interest for applications that require low magnetic permeability, low-temperature cryogenic strength, and low-temperature toughness. The corresponding loss in yield strength due to the reduced C level is compensated by alloying with elements such as N, Cr, V, Mo, and Ti. The stacking fault energy (SFE), tensile strength, and yield strength of binary Fe-Mn alloys are influenced by ˜ AS, Graduate Student, and J. PENNING, Professor, are with N. CABAN the Laboratory for Iron and Steelmaking, Department of Metallurgy and Materials Science, Ghent University, B-9052 Ghent, Belgium. N. AKDUT is with the Arcelor Group, OCAS NV, B-9060 Zelzate, Belgium. B.C. De COOMAN, Professor, is with the Graduate Institute of Ferrous Technology, POSTECH, Pohang, Kyung Buk 790-784, Korea. Contact e-mail: [email protected] Manuscript submitted January 24, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS A
the Mn content.[1,2] These properties can be related to the specific microstructures that are observed within characteristic Mn ranges. Figure 1 gives a schematic overview of the Fe-Mn binary system. Depending on the Mn level, the following microstructures are formed. (1) For Mn contents up to 2 pct, a single-phase ferritic microstructure is formed. This structure is characterized by a low strength and a high ductility. The solid solution hardening effect of Mn on the yield strength of C-Mn alloys has been reported to be 26.1 MPa/pct Mn3. In C-steel, the additional effects of Mn on the grain size and the amount of pearlite must also
Data Loading...
