Conditions for Hot Rolling of Iron Aluminide

Abstract

Iron aluminides are known to be a prospective material which is very often used also abroad (e.g. in the U.SA., Japan, Germany, France, Spain). [1] Iron aluminides are applied as structural materials due to their low material cost (as compared to corrosion-and heat-resistant steels which contain high amount of additives ± Cr, Ni, etc.), low specific mass, excellent resistance against oxidizing and sulfidizing environment at temperatures above 600 C. [1] The drawbacks of iron aluminide based alloys is the low ductility at room temperature. The elimination of this disadvantage and the improvement of some properties may be achieved by the method of processing and by the modification of the composition by appropriate alloying, e.g. with chromium, cerium, niobium, titanium boride, zirconium, etc. The properties of intermetallics may be also improved by cold and/or hot rolling and by heat treatment.Sheet manufacturing and study of their properties is important for some applications, namely corrosion-resistant thin sheets (even at high temperatures) may be applied e.g. as protective cladding on components exposed to corrosion environment. Therefore softening processes were studied during hot rolling of Fe28Al4Cr (at.%) alloy.Mathematical models, which describe the rolling process of the intermetallic iron aluminide, are derived from the test results. The main point is to describe the mean equivalent stress in dependence on strain, temperature and strain rate. The simplest models were created for cold forming, provided that power stress-strain relationship is sufficient in this case. [2] Many authors have tried by involving the influence of temperature (exponential relationship), strain rate (power relationship) and of influence of dynamic softening to extend finally the range of applied strains [3±8] .The present paper is based on the above knowledge and describes the rolling experiments to determine the optimum rolling conditions, which should result in pilot tests allowing the controlled manufacturing of sheets. The basic task is the determination of the mean equivalent stress combined with the observation of the substructure verifying the physical processes necessary for enough softening during the hot rolling.Most experiments were based on laboratory rolling of flat samples with the graded thickness ( Fig. 1), which were used for determination of mean equivalent stress or microscopic examination of structures originated during forming. An advantage of the sample with thickness graded in size is four times higher quantity of data achieved by its rolling at exactly defined temperature as compared with rolling of one flat sample with the constant thickness.Each sample was heated in the electric resistance furnace to the forming temperature. Then it is immediately rolled in the laboratory mill (diameter of plain work rolls 159 mm) with the adjusted temperature, roll gap and nominal revolutions of rolls. Rolling force and instantaneous revolutions of rolls are registered (Fig. 2). All measured variables are recalculated...

Load-Independent Hardness and Indentation Size Effect in Iron Aluminides

“…The molten alloy was then cast into a shell mold, followed by rolling at 1200 • C to achieve half thickness. This procedure has been comprehensively detailed in previous studies conducted by Kratochvil et al [13,30,31]. The resulting flat work attained a final thickness of 15.2 mm.…”

“…Structural applications are especially advantageous when high-temperature-resistant components are required due to the high melting and disordering temperatures, high stiffness, and low diffusivity of ICs [10,11]. Moreover, IC may have also been applicable for ballistic protection due to relatively low density (aluminide ICs), high strain hardening rate, enhanced oxidation and temperature resistance, and some formulations containing minimal or no critical raw materials [12,13]. The determination of the mechanical properties of structural ICs is well covered with standards and procedures.…”

Iron Aluminides

“…The possibility of producing plates, sheets, and tapes by hot and cold rolling of iron aluminides has been frequently demonstrated (14,(253)(254)(255). Alloys with an Al content of up to approximately 30-at% Al may be processed according to the parameters used for rolling of Cr steels (129,256). At higher Al contents, the rolling resistance becomes too high so that spacers have to be used or the alloys have to be canned (257,258).…”

Deformation resistance and structure-forming processes of iron aluminides in hot rolling

“…After cooling down of the rolled stock, the width and thickness of individual specimens were also measured. All the recorded variables mentioned above were presented in the table and recalculated to obtain the values of the equivalent (logarithmic) height reduction e h , strain rate & e (in s −1 ) and MES σ m (in MPa) [3].…”