Tensile behavior of functionally graded steels produced by electroslag remelting
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ALTHOUGH considerable attention has been drawn to produce functionally graded materials (FGMs),[1,2] it seems that the utility of FGMs with metallic base is yet to be investigated. Functionally graded steels (FGSs) were originally produced from austenitic stainless steel and carbon steel base materials using electroslag remelting.[3] Microstructural studies of the FGSs have shown that it is possible to obtain multilayered composites consisting of ferrite, austenite, bainite, and martensite. By selecting the appropriate arrangement and thickness of the initial ferritic and austenitic steels used to set up the electrodes, it is possible to control the variety and thickness of the merging phases after remelting. When the primary electrode contains two slices of ferritic and austenitic layers as (a0g0), the morphology of the resultant composite is (abg); hence, R
ða0 g 0 Þel ""! ðabgÞcom where a 5 ferretic layer, g 5 austenitic layer, b 5 bainitic layer, el 5 electrode, com 5 composite, and R 5 remelting. Similarly, when the primary electrodes contain three slices of ferretic and austenitic steels, the following phases appear in the final composite after remelting: R
ða0 g0 a0 Þel ""! ðabgbaÞcom R
ðg 0 a0 g0 Þel ""! ðgMgÞcom
J. AGHAZADEH MOHANDESI, Associate Professor, and R. PARASTAR NAMIN, Postgraduate Research Student, are with the Department of Mining and Metallurgical Engineering, Amir Kabir University of Technology, Tehran, Iran. Contact e-mail: [email protected] or [email protected] M.H. SHAHOSSEINIE, Assistant Professor, is with the Faculty of Engineering, Department of Metallurgy, University of Tehran, Tehran, Iran. Manuscript submitted August 29, 2005. METALLURGICAL AND MATERIALS TRANSACTIONS A
where M 5 martensitic layer. Finally, by using four slices of austenitic and ferretic steels, it follows that R
ða0 g0 a0 g 0 Þel ""! ðabgMgÞcom R
ðg0 a0 a0 g0 Þel ""! ðgbabgÞcom Diffusion of chromium, nickel, and carbon atoms taking place at the remelting stage in the liquid phase controls the chromium, nickel, and carbon atom distribution pattern in the produced composites. As alloying elements diffuse, alternating regions with different transformation characteristics are created. The diffusing atoms individually or together stabilize different phases such as bainite or martensite. The transformation characteristics of FGSs have already been presented.[3] In this work, the tensile behavior of these composites is studied.
II.
EXPERIMENTAL METHOD
An experimental electroslag remelting apparatus was set up to produce FGSs. A mixture of 20 pct CaO, 20 pct Al2O3, and 60 pct CaF2 was used as the slag. Consumable electrodes consist of slices of AISI 1020 and AISI 316 steels (called alfa, a0 and gamma, g0 steel in this work, respectively) with chemical compositions as given in Table I. The height of slices was 25 mm in four-piece, 50 mm in two-piece, and 25 mm and (37.5 3 2) mm in three-piece electrodes. The remelting procedure was carried out under a constant power supply of 16 kVA. Cylindrical specimens with up to four
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