Iron-aluminum Alloys Research Articles

Mechanical properties and oxidation behaviour of two-phase iron aluminium alloys with Zr(Fe,Al) 2 Laves phase or Zr(Fe,Al) 12 τ 1 phase

Two-phase Fe-rich Fe–Al–Zr alloys have been prepared consisting of binary Fe–Al with a very low solubility for Zr and the ternary Laves phase Zr(Fe,Al) 2 or τ 1 phase Zr(Fe,Al) 12. Yield stress, flexural fracture strain, and oxidation behaviour of these alloys have been studied in the temperature range between room temperature and 1200 °C. Both the Laves phase and the τ 1 phase act as strengthening phases increasing significantly the yield stress as well as the brittle-to-ductile transition temperature. Alloys containing disordered A2+ ordered D0 3 Fe–Al show strongly increased yield stresses compared to alloys with only A2 or D0 3 Fe–Al. The binary and ternary alloys with about 40at.% Al and 0 or 0.8at.% Zr show the effect of vacancy hardening at low temperatures which can be eliminated by heat treatments at 400 °C. At higher Zr contents this effect is lost and instead an increase of low-temperature strength is observed after the heat treatment. The increase of the high-temperature yield strength of Fe-40at.% Al by adding Zr is much stronger than by other ternary additions such as Ti, Nb, or Mo. Tests on the oxidation resistance at temperatures up to 1200 °C indicate a detrimental effect of Zr already for additions of 0.1at.%.

Observation of exothermic reaction during laser-assisted iron oxide coating on aluminum alloy

Abstract Aluminum and Fe 3 O 4 reacts readily in what is known as thermite reaction to produce large amount of heat. Attempts were made to coat Fe-oxide on A319 cast aluminum alloy employing a high power laser to exploit this reaction. High-speed, high-resolution infrared thermography was employed to study the thermal conditions during the laser treatment. Parallel experiment using a less exothermic oxide (FeO) and the same substrate further emphasized development of higher temperature during highly exothermic reaction. The cooling rate calculated via both steady state and non-steady state relations were one order of magnitude different, which was supported by microstructural observations. Transmission electron microscopy revealed formation of aluminides as a result of reaction between iron oxide and aluminum alloys.

Microstructure and properties of iron aluminum alloy/CrMo steel composite prepared by clad rolling

The composite steel sheet of iron aluminum alloy and CrMo steel was produced by clad rolling, in which fabrication condition was determined by deformation resistance between the constituents derived from high temperature compression test at a high strain rate. Flow stress ratio of iron aluminum alloy to CrMo steel increases at low temperatures due to high flow stress of iron aluminum alloy, while, the ratio is within the criterion for simultaneous deformation of different materials proposed by Gomez and Echeberria [Mater. Sci. Eng. A 348 (2003) 180]. Three layered composite steel sheet consisting of alloy/steel/alloy was fabricated by clad rolling at 873 or 1273K, and exhibits superior bending deformability. The composite steel could be cold rolled to 120μm thickness (99.8% reduction), and wound to a coil without damage. It is concluded that composite steel thin sheet can be produced by controlling composition of iron aluminum alloy and clad rolling condition.

Iron Aluminium Alloys with Strengthening Carbides and Intermetallic Phases for High-Temperature Applications

An overview of materials developments of iron aluminium alloys with strengthening precipitate phases is given. The discussion is focussed on recent studies on Fe-Al-based alloys with strengthening precipitates, such as K-phase Fe 3 AlC x , MC-carbide and Laves phase. Alloys of the following alloy systems were investigated: Fe-Al-C, Fe-Al-Ta, Fe-Al-Ni, Fe-Al-Ti-Nb, and Fe-Al-M-C (M = Ti, V, Nb, Ta). The investigations were centred on microstructure, constitution, and mechanical properties of such Fe-Al-based alloys with Al contents ranging from 10 to 30 at. %. Mechanisms and problems are discussed and perspectives are outlined.

Strengthening of iron aluminide alloys for high-temperature applications

ABSTRACTAn overview is given on materials developments of ferritic and Fe3Al-based iron aluminium alloys with strengthening precipitate phases for high-temperature applications currently underway at the Max-Planck-Institut für Eisenforschung GmbH (MPIE). The development of high-temperature alloys for structural applications is to be focussed on optimisation of strength, creep and corrosion resistance at high temperatures and sufficient ductility at lower temperatures. This is discussed with respect to recent studies on Fe-Al-based alloys with strengthening precipitates, such as κ-phase Fe3AlCx, MC-carbides, Laves phase, and the B2-ordered intermetallic phase NiAl. The following alloy systems have been investigated: Fe-Al-X (X=C, Ti, Ta, Mo, Zr), Fe-Al-Ti-Nb, Fe-Al-Ni-Cr, and Fe-Al-M-C (M=Ti, V, Nb, Ta).The investigations have been focussed on the microstructure, constitution, mechanical properties, and high-temperature corrosion behaviour of Fe-Al-based alloys with Al contents ranging from 10 to 30 at. %.

Nanostructured Al–Fe alloys produced by e-beam deposition: static and dynamic tensile properties

Three different aluminum–iron alloys were produced by electron-beam deposition with the iron content in the range 1.15–1.71 at.%. These alloys did not contain any identifiable iron-bearing particles, and exhibited full density with high-angle grain boundaries in the micrometer range, and a sub-grain size typically smaller than 100 nm. The tensile deformation characteristics of the alloys were examined at a dynamic strain rate of 1.1×10 3 s −1 and a quasi-static strain rate of 1×10 −3 s −1 at room temperature. The alloy containing 1.7% Fe exhibited an abnormally high tensile strength of about 950 MPa with a ductility of up to 6%. Detailed atomic resolution imaging of the structure of the alloys has been performed along with an examination of their fracture surface features. The fracture surfaces of the alloys showed ductile dimples which typically spanned five to 10 times the sub-grain diameter. It is postulated that the nano-scale sub-grains of the alloy impart high strength, while the structure associated with high-angle boundaries provides reasonable ductility. Possible mechanisms responsible for the high strength in the present Al–Fe alloys are explored. The present results are also examined in conjunction with a comprehensive survey of available results on the strain-rate sensitivity of tensile yield strength and ductility in microcrystalline, sub-microcrystalline and nanocrystalline metals and alloys, and on the solid-solution strengthening of aluminum alloys.

Deformation behaviour of iron-rich iron-aluminium alloys at high temperatures

The deformation behaviour of binary monocrystalline and polycrystalline Fe-Al alloys with Al contents up to 18 at.% and only low unavoidable impurity contents—in particular less than 100 wt.ppm C—has been studied above room temperature up to 800 °C. The effects of quenching and annealing treatments on the behaviour of as-cast materials were investigated in order to clarify the dependence of strength and ductility on Al content and possible short-range ordering. Besides solid-solution hardening by Al, serrated yielding and deformation twinning were observed at high temperatures. Yielding is affected by quenched-in excess vacancies.

Structure and properties of PM aluminium-iron alloys processed by mechanical alloying: M. Sugamata et al. (Nihon University, Narashino, Japan.) J. Japan Soc. Powder/Powder Metall., Vol 49, No 1, 2002, 19–24. In Japanese

Structure and properties of PM aluminium-iron alloys processed by mechanical alloying: M. Sugamata et al. (Nihon University, Narashino, Japan.) J. Japan Soc. Powder/Powder Metall., Vol 49, No 1, 2002, 19–24. In Japanese

Deformation behaviour of iron-rich iron-aluminum alloys at low temperatures

The deformation behaviour of binary monocrystalline and polycrystalline Fe-Al alloys with Al contents up to 18 at.% and only low unavoidable impurity contents—in particular less than 100 wt.ppm C—has been studied at room temperature and −100 °C. The effects of quenching and annealing treatments on the behaviour of as-cast materials were investigated in order to clarify the dependence of strength and ductility on Al content and short-range ordering. It was found that the stress-strain behaviour at low temperatures is controlled primarily by Al solid-solution hardening and quenched-in excess vacancies with only minor effects of short-range ordering.

Effect of Al on the Long-Term Oxidation Behavior of Fe-0.5C Alloys

Electroslag remelted cast iron-aluminum alloys having the compositions: 1) Fe-16Al-0.5C, 2) Fe-10Al-0.5C, and 3) Fe-8Al-0.5C were employed to investigate the effect of Al on the oxidation behavior of Fe-0.5C alloys in the temperature range 973 - 1273 K. Microstructural and phase analyses of these alloys revealed distribution of a carbide phase, Fe 3 AlC 0.692 in the Fe 3 Al matrix of alloy 1 and in Fe-Al matrix of alloys 2 and 3. The oxidation behavior of these alloys was found to be dependent upon relative composition and stability of the carbide and matrix phases. High-Al content alloys were free from decarburization, whereas low-Al content alloys suffered from decarburization.

Laser-Assisted Surface Modification of 4340 Steel with Iron-Aluminum Alloys

ABSTRACTHigh power Nd-YAG laser was used to fuse coatings containing a mixture of FeAl and Al, with 4340 steel. It was observed that good quality coatings could be obtained using this process. Detailed microstructural studies show that Fe aluminides and/or a solid solution of Al in Fe can form within the coating, depending on the processing conditions. Wear measurements show that the best wear properties are obtained in the presence of an aluminide in the coating and that the wear properties significantly degrade when the coating consists primarily of a solid solution of Al in Fe.

Composed Phases and Microhardness of Aluminium-Rich Aluminium-Iron Alloys Obtained by Rapid Quenching, Mechanical Alloying and High Pressure Torsion Deformation

ossbauer spectroscopy. The alloys were prepared by various techniques: remelting, accelerated cooling by centrifugal casting, rapid quenching from the melt at a rate of 10 6 K/s, and mechanical alloying of pure elements in high-energy planetary ball mill. It is shown that the crystalline structure refinement and the composed phases of the alloys essentially depend on the techniques used for the sample preparation. Phase transformations by severe plastic torsion deformation of the alloys prepared by various techniques were studied. The highest supersaturation of Fe in the aluminium-based solid solution can be reached using two subsequent techniques of alloy treatment: rapid quenching and high-pressure torsion.

Chemical interaction of Fe and Al(2)O3 as a source of heterogeneity at the Earth's core-mantle boundary.

Seismological studies have revealed that a complex texture or heterogeneity exists in the Earth's inner core and at the boundary between core and mantle. These studies highlight the importance of understanding the properties of iron when modelling the composition and dynamics of the core and the interaction of the core with the lowermost mantle. One of the main problems in inferring the composition of the lowermost mantle is our lack of knowledge of the high-pressure and high-temperature chemical reactions that occur between iron and the complex Mg-Fe-Si-Al-oxides which are thought to form the bulk of the Earth's lower mantle. A number of studies have demonstrated that iron can react with MgSiO3-perovskite at high pressures and high temperatures, and it was proposed that the chemical nature of this process involves the reduction of silicon by the more electropositive iron. Here we present a study of the interaction between iron and corundum (Al(2)O3) in electrically- and laser-heated diamond anvil cells at 2,000-2,200 K and pressures up to 70 GPa, simulating conditions in the Earth's deep interior. We found that at pressures above 60 GPa and temperatures of 2,200 K, iron and corundum react to form iron oxide and an iron-aluminium alloy. Our results demonstrate that iron is able to reduce aluminium out of oxides at core-mantle boundary conditions, which could provide an additional source of light elements in the Earth's core and produce significant heterogeneity at the core-mantle boundary.

Effect of hot rolling and heat treatment on structure and properties of high carbon Fe–Al alloys

Iron–aluminium alloys with the following compositions, Fe–8.26 wt.% Al–0.46 wt.% C, Fe–7.2 wt.% Al–1.1 wt.% C, Fe–11.20 wt.% Al–0.5 wt.% C and Fe–10.83 wt.% Al–1.1 wt.% C were melted under a flux cover by air induction melting (AIM). The AIM ingots were subsequently processed through electroslag remelting (ESR). Both AIM and ESR ingots were hot forged and hot rolled at 1375 K to 92% reduction. ESR ingots exhibited better hot workability as compared with AIM ingots. This may be due to the axially oriented columnar grain structure relatively free from internal defects such as microporosity and non metallic inclusions observed in ESR ingots. About 14 ml thick ESR processed alloys in the hot-rolled condition also exhibited superior room temperature tensile elongation as compared with hot-rolled AIM alloys. This may be attributed to the comparatively homogeneous, clean ingot with a refined microstructure and a fine uniform distribution of Fe 3AlC 0.5 phase as observed after ESR. Further rolling of the ESR alloy to a 4-mm thickness has resulted in significant improvements in strength. The tensile elongation of hot rolled ESR alloys was reduced after heat treatment except in the case of Fe–7.2 wt.% Al–1.1 wt.% C alloy which exhibited a 17% improvement.

Acoustic-Emission Methods for Assessing the Process of Damage Accumulation in Estimating Remaining Service Lives of Heavily Loaded Structures

The paper is dedicated to estimating parameters of the process of damage accumulation on the base of restored frequencies of acoustic emission (AE) events and invariant AE destruction criteria. Experimental investigation of relations between AE parameters and features of early stages of fracture of layered composite materials and iron–aluminum alloys are presented. The paper describes a method for identification of destruction stages and prediction of remaining service lives based on AE measurements.

Physical and mechanical properties of iron-aluminium-(Mn, Si) lightweight steels

Iron-aluminium alloys containing up to 9 wt- for the development of high performance lightweight steels for automotive applications and for building constructions. Some of these alloys have a b.c.c. structure and have interesting physical and mechanical properties. Macro-alloying with manganese favours the formation of the austenite phase. Micro-alloying and thermomechanical processing including texture development will improve the plastic anisotropy properties and the strain hardening exponent.

Measurement and Calculation of Nitrogen Removal Rate from Molten Iron to Gas Phase through CaO-Al2O3 Melts

There is a limit for lowering nitrogen in steel because of pickup from atmosphere during and after degassing. Therefore, nitride capacity of various fluxes has been measured in order to examine the possibility of nitrogen removal by using slag. It is necessary to take into account the nitrogen reaction rate between gas and slag phases and know the nitrogen behavior through successive phases of metal, slag, and gas for the efficient removal of nitrogen in practical steelmaking process. In this study, nitrogen removed rate from molten iron-aluminum alloy to gas phase through CaO-Al2O3 melts has been examined and a mixed rate determining model has been applied through successive phases of metal, slag, and gas taking gas/slag reaction rate into consideration. For the effective removal of nitrogen from metal to gas phase through CaO-Al2O3 melts, it is important to keep oxygen pressure in the gas phase higher and oxygen potential at slag/metal interface lower.

Three-dimensional atomic-scale imaging of impurity segregation to line defects

Clouds of impurity atoms near line defects are believed to affect the plastic deformation of alloys. Three-dimensional atom probe techniques were used to image these so-called Cottrell atmospheres directly. Ordered iron-aluminum alloys (40 atomic percent aluminum) doped with boron (400 atomic parts per million) were investigated on an atomic scale along the <001> direction. A boron enrichment was observed in the vicinity of an <001> edge dislocation. The enriched region appeared as a three-dimensional pipe 5 nanometers in diameter, tangent to the dislocation line. The dislocation was found to be boron-enriched by a factor of 50 (2 atomic percent) relative to the bulk. The local boron enrichment is accompanied by a strong aluminum depletion of 20 atomic percent.

In-situ production and microstructures of iron aluminide/TiC composites

In this study we have tried to produce the titanium carbide reinforced iron aluminide composites by in-situ reaction between titanium and carbon in liquid iron–aluminum alloy doped with titanium and carbon. A homogeneous distribution of titanium carbide particles in the iron aluminide matrix up to about 16 vol% of titanium carbide was intended without agglomeration. The composition of TiC formed during in-situ reaction was investigated by ICP analysis and the Combustion-Infrared Absorption method after chemical dissolution of the iron aluminide matrix. It is found that the composition of titanium carbide formed during melt processing is an average of Ti–48.4 mol% C. In addition, titanium carbide has very low solubility of Fe and Al. The microstructure of composites consists of three different regions; primary large TiC particles of 5–40 μm, matrix with small dendritic TiC particles of about 1 μm and particle-free regions around primary large TiC particles. The formation of this complex microstructure can be explained by assuming the Fe 3Al–TiC pseudo-binary system containing the eutectic reaction. Particle-free regions are halos of iron aluminide phase and the formation of halos is explained by coupled zone concept. Subsequent heat treatment at 1373 K for 48 h induces spheroidization and/or coarsening of small TiC particles, while microstructure after heat treatment at 973 K for 48 h exhibits the additional formation of small TiC precipitates. Though excess 1 mol% Ti addition over the Ti content for TiC formation is soluble to Fe–28 mol% Al, excess 1 mol% C addition forms the secondary Fe 3AlC phase during melt processing.

Development of a soft magnetic iron-aluminium alloy for automotive applications: T.Nielson et al. (Williams International, USA.)

Development of a soft magnetic iron-aluminium alloy for automotive applications: T.Nielson et al. (Williams International, USA.)