On the inhomogeneity of the crystallographic rolling texture of polycrystalline Fe 3 Al
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On the inhomogeneity of the crystallographic rolling texture of polycrystalline Fe3 Al D. Raabea) and J. Keichel Institut f¨ur Metallkunde und Metallphysik, Kopernikusstr. 14, RWTH Aachen, 52056 Aachen, Germany (Received 23 January 1995; accepted 29 February 1996)
An intermetallic Fe3 Al alloy was cast, hot rolled, annealed (870 K), and finally quenched. After this treatment, the alloy had an imperfectly ordered B2 structure. The polycrystalline sample was then warm rolled at 800–830 K. The crystallographic texture of the rolled specimen was quantitatively studied within the range, e 20–80%. Even at large strains (e 80%), recrystallization was not observed in the microstructure. It was found that the rolling texture of Fe3 Al is very inhomogeneous through the sample thickness. In the center layer, a large volume fraction of grains with a h111j lattice plane parallel to the sheet surface, h111j kuvwl, and a weak h001j k110l component were observed. In contrast, close to the sheet surface layer, a weak texture containing the h11 11 8j k4 4 11l and the h012j k110l orientations was formed. The results are interpreted in terms of the activation of h110j k111l and h112j k111l slip systems. The throughthickness texture gradient was attributed to the inhomogeneous strain distribution during rolling, leading to plane strain in the center layer and to shear strains close to the surface.
I. INTRODUCTION
Intermetallic iron aluminides with compositions near that of Fe3 Al with imperfect B2 or DO3 structure were thoroughly studied in the past due to their excellent oxidation and sulfidation resistance and good mechanical properties at low and elevated temperature.1–13 According to the equilibrium phase diagram of Fe and Al, Fe3 Al reveals an imperfectly ordered B2 (FeAl) structure at T . 823 K and an ordered DO3 (Fe3 Al) structure at T , 823 K (Fig. 1).14 However, at ambient and even at elevated temperatures below 823 K, the B2 structure can be preserved through a special thermomechanical treatment.11–13 The DO3 phase transformation is typically very slow.7,11–13 In the presence of ternary additions like Cr, Mo, Zr, Nb, C, and B, the phase transformation from B2 to DO3 may even be entirely suppressed.11–13 The production of Fe3 Al requires relatively small material costs, and the alloy reveals a better strength-to-weight ratio than stainless steels.7 Because of the control of microstructure and composition, the mechanical properties and the corrosion resistance were considerably improved, especially the room temperature ductility and the strength at elevated temperatures.7 For studying plastic deformation of polycrystalline Fe3 Al based alloys, mainly three techniques were employed in the past. First, the influence of the antiphaseboundary energy was assessed on the selection of slip systems.7,15 Second, slip trace investigations on polished sample surfaces were analyzed, and third, transmission
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