Microstructural and mechanical behavior of a duplex stainless steel under hot working conditions
- PDF / 1,715,056 Bytes
- 12 Pages / 612 x 792 pts (letter) Page_size
- 3 Downloads / 257 Views
INTRODUCTION
THE duplex stainless steels are materials that present a better combination of mechanical properties and stress corrosion resistance than ferritic and/or austenitic stainless steels.[1] However, in the processing of these materials, hot working is a critical step that leads in many cases to the presence of cracks and/or an unacceptable surface finish. The deformation behaviors of the ferrite and the austenite inside the duplex structure are modified by the presence of the other phase. This, in addition to the different mechanical properties of both phases, the austenite being significantly stronger than the ferrite in the hot working temperature range, will affect the load transfer between both constituents and therefore the hot strength and ductility of the duplex stainless steels.[2] In the hot working operations, such as rolling, the schedules of deformation consist of a series of deformation passes and holding times. During this hot working sequence, microstructural changes related to the phase proportions, orientation, and morphology can take place, at the same time that the dynamic and static recovery and recrystallization act in the two ductile phases, ferrite and austenite.[2–5] The effects of dynamic and static recovery and recrystallization have been extensively studied by numerous authors in ferrite and austenite single-phase materials.[6–10] However, behavioral differences are expected when the two phases are in a duplex stainless steel. For example, recrystallisation kinetics is significantly modified when both phases are present in a duplex stainless steel[11] and in particular the dynamic recrystallisation of the austenite has ˜ OL-JUEZ, Doctoral Students, are with the A. IZA-MENDIA and A. PIN Department of Materials, Centro de Estudios e Investigaciones Te´cnicas de Gipuzkoa (CEIT), 20009 San Sebastia´n, Spain. A. IZA-MENDIA is also with ESII, University of Navarra. J.J. URCOLA, formerly Head, Department of Materials, CEIT, and Professor, Escuela Superior de Ingenieros Industriales (ESII), University of Navarra, 20009 Donostia-San Sebastian, Basque Country, Spain, is deceased. I. GUTIE´RREZ, Senior Researcher, is with the Department of Materials, CEIT, and with ESII, University of Navarra. Manuscript submitted December 23, 1997. METALLURGICAL AND MATERIALS TRANSACTIONS A
been found to be significantly hindered in such a condition.[3,4] The morphology of the constituent phases changes during hot rolling from a dendritic structure in the as-cast material to an elongated grain or ‘‘pancake’’ type of structure with alternate ferrite and austenite regions in the wrought steel. The aspect ratio of both phases depends on the imposed hot reduction during rolling. The material behavior will depend on the phase morphology with respect to the imposed strain. There are several works[13–17] that attempt to describe the plastic deformation behavior of two ductile phase alloys, by taking into account the influence of the phase morphology on the overall flow stress of a two-phase alloy. Vernuse and M
Data Loading...
