An evaluation of two experimental duplex CrMnN stainless steels after thermo-mechanical processing

This paper examines work carried out on two experimental, metastable, dual-phase stainless steels, alloyed with Mn and N, for the purpose of improving their strength while maintaining reasonably high ductility and toughness. Two different treatments were applied to the alloys, the first being cold rolling to provide a basis for comparative purposes. This resulted in the transformation of varying amounts of the metastable austenite to martensite and also produced work-hardening, while the second, a thermo-mechanical treatment in the form of warm rolling, was applied in order to provide work hardening whilst inhibiting the formation of deformation induced martensite. This treatment resulted in slightly lower 0.2% proof and tensile strengths than those obtained from an equivalent amount of cold deformation. The high ductilities of the undeformed materials were, however, nearly maintained, resulting in an excellent overall improvement in mechanical properties. Both treatments resulted in a decrease in the corrosion resistance of the alloys, although the decrease arising from the thermo-mechanical treatment was less than that brought about as a result of cold working. Warm working was thus considered to be a very useful technique for obtaining improved mechanical properties without detrimentally affecting the corrosion resistances of the materials investigated.