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Microstructures, mechanical properties and oxidation behaviour of single-phase Fe 3 Al (D0 3 ) and two-phase α-Fe,Al (A2) + Fe 3 Al (D0 3 ) Fe Al V alloys have been studied. Alloying with vanadium substantially increases the strength of the single-phase alloys through solid solution hardening. In addition, vanadium markedly increases the D0 3 /B2 transition temperature. The change from B2 to D0 3 at a given temperature yields an additional increase in strength. The two-phase alloys have a fine-scaled coherent microstructure with D0 3 precipitates ranging between 10 and 30 nm in the as-cast state. However, marked coarsening of D0 3 is observed after annealing at 700 °C for 1000 h. Up to this temperature the alloys show an appreciable flow stress and creep strength, comparable to those of other iron aluminide based alloys with coherent microstructures. Oxidation tests at 700–900 °C revealed formation of thick and porous Fe 2 O 3 + Al 2 O 3 scales above 700 °C. Therefore, above 700 °C the oxidation behaviour of these alloys is inferior compared to that of other iron aluminide alloys with about the same Al content. This poor oxidation behaviour does not improve when 4–8 at.% Cr are added. [ABSTRACT FROM AUTHOR]

Abstract: The corrosion resistance of Fe–Al and Fe–Al–X alloys under neutral salt spray conditions has been evaluated. For the binary alloys the corrosion resistance constantly improved up to an Al content of about 30 at.%. While higher Al contents did not better the corrosion resistance it may be further improved by addition of passivity-inducing elements. The phases that formed on the various alloys have been identified. Particularly small weight losses after neutral salt spray testing were observed for those alloys where thin and dense layers of Fe3O4 (magnetite) had formed on the surfaces during the tests. [Copyright &y& Elsevier]

Abstract: The oxidation behaviour of two Fe3Al-based Fe–Al–Cr–Zr–C alloys has been evaluated between 900 and 1200°C. The alloys contained either (Fe,Al)2Zr Laves phase or ZrC carbide. The alloys were oxidised for up to 1000h in synthetic air using thermogravimetric analysis (TGA). Scales that formed on the surfaces of the sample as well as cross sections were analysed by light optical microscopy (LOM), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectrometry (EDS). At 900°C parabolic growth and low weight gains for both tested alloys were observed. The scales are predominantly formed by Al2O3 with minor amounts of ZrO2. Some Fe2O3 was observed after oxidation at 900°C. At 1000°C oxidation ingresses into the samples along grain boundaries due to preferential oxidation of the Zr-rich precipitates, becoming more severe at higher temperatures. Ingress of oxidation into the sample is more pronounced for the alloy containing ZrC where at 1200°C it is not any longer limited to the carbide but extends markedly into the Fe3Al matrix. [Copyright &y& Elsevier]

Abstract: The formation and stability of Al-rich Ti–Al phases is reviewed and the kinetics of the phase transformations and evolution of lamellar TiAl+r-TiAl2 microstructures is discussed. For this a couple of Ti–60at.% Al alloys were processed by different techniques to generate different initial microstructures. The kinetics were studied by annealing the differently processed alloys for 1, 10, 100 and 1000h at temperatures between 800 and 1000°C and then analysing the quenched microstructures by optical, scanning electron, and transmission electron microscopy. In addition, in situ heating and cooling experiments using differential thermal analysis and transmission electron microscopy were performed to verify the results obtained for the quenched samples. The results conclusively show why the metastable phases h-TiAl2 and Ti3Al5 form. The stability and transformation of the metastable phases have been determined in dependence on time and temperature and the kinetics of the two different mechanisms by which the stable phase r-TiAl2 forms have been established. The effects of differing initial microstructures on the evolution of the microstructure with time and temperature are discussed. [Copyright &y& Elsevier]

Abstract: The high-temperature oxidation behaviour of Fe–25Al–2Ta (in at.%) has been investigated between 600 and 1000 °C using thermogravimetric analysis (TGA) in synthetic air. After oxidation for 1000 h the scales were analysed by light optical microscopy (LOM), grazing incidents X-ray diffraction (GI-XRD), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Between 600 and 800 °C thin adherent oxide scales grew according to a parabolic rate law. At 900 °C parabolic growth was observed for several hundred hours, interrupted by sudden mass gains which are probably caused by cracking of the scales, while at 1000 °C no protective scales formed. The scales are predominantly formed by Al2O3 and minor amounts of Fe2O3. While scales formed between 600 and 800 °C are still adherent after cooling to room temperature, scales formed at higher temperatures spalled during/after cooling, possibly because the Laves phase Fe2Ta formed on the sample surfaces underneath the oxide scales. Parabolic rate constants kp show that compared to other Fe–Al alloys addition of 2 at.% Ta has no detrimental effect to the excellent oxidation resistance in air between 600 and 800 °C. [Copyright &y& Elsevier]

Abstract: During investigations of the mechanical properties of L21-ordered Fe–Al–Ti-based alloys, a two-fold flow stress anomaly has been detected. This stress anomaly is marked by two distinct flow stress peaks at around 500 and 750°C. While the peak at about 750°C has been reported before, the occurrence of a second peak is reported for the first time. It has been investigated by means of compression tests at various compression rates and after different heat treatments of the alloys, measurements of the hardness after water quenching from relevant temperatures and by differential thermal analysis. The results give no clear insight into the mechanism of this two-fold anomaly. However, it can be seen that aging at around 500°C and increasing the compression rate from 10−4 to 10−2 s−1 have an effect on the phenomenon. [Copyright &y& Elsevier]

Abstract: The Al–Fe–Ti system has been assessed and the limiting binary systems are shortly reviewed. Based on a thorough review of the literature, isotherms at 800, 900, and 1000°C have been re-evaluated and a provisional isotherm at 1200°C is presented for the first time. The effect of alloying the binary phases with the third component is reviewed with regard to the ternary homogeneity ranges, crystallography, order/disorder transformations, and site occupancies. Of the variously reported ternary compounds only the existence of “Al2FeTi” (τ2) and “Al8FeTi3” (τ3) is confirmed. The occurrence of the phases τ2 ∗, τ′2, and of a new stacking variant of TiAl is still under discussion, while the existence of the phases Fe2AlTi (τ1) and Fe25Al69Ti6 (X) is ruled out. The presented reaction scheme corroborates the isothermal sections and also a representation of the liquidus surface is given. Magnetic, electrical, thermochemical, atomistic and diffusion data for Al–Fe–Ti alloys are summarised and an overview about studies on modelling of phase equilibria and phase transformations is given. [Copyright &y& Elsevier]

Abstract: Fe–Al-based alloys, i.e. alloys which contain either disordered A2 α-(Fe,Al), B2-ordered FeAl or D03-ordered Fe3Al as majority phase, have a considerable potential for developing materials for structural applications, but insufficient strength and creep resistance have been identified as obstacles for the use of Fe–Al-based alloys at high temperatures. At the ‘Discussion Meeting on the Development of Innovative Iron Aluminium Alloys’ held at the Max-Planck-Institut für Eisenforschung GmbH, Düsseldorf on March, 9th 2004 a couple of presentations were made with emphasis on improving these properties at high temperatures. In the current article those strengthening mechanisms which are provided by the phase diagram—solid-solution hardening, strengthening by precipitates, or ordering—are reviewed. Besides results obtained for the binary Fe–Al system special emphasis is put forward to those ternary systems for which results have been presented at the ‘Discussion Meeting’. [Copyright &y& Elsevier]

Abstract: 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 τ1 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 τ1 phase act as strengthening phases increasing significantly the yield stress as well as the brittle-to-ductile transition temperature. Alloys containing disordered A2+ ordered D03 Fe–Al show strongly increased yield stresses compared to alloys with only A2 or D03 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.%. [Copyright &y& Elsevier]

Abstract: In Part I, various models for the prediction of the occurrence and stability of Laves phases have been discussed. In the present Part II paper, an overview is given on the various types of manifestation of Laves phases in intermetallic alloy systems with emphasis on transition metal systems. Temperature- and composition-dependent as well as stress-induced phase transformations between the cubic C15 and the hexagonal C14 and C36 structural polytypes of Laves phases were observed in various binary and ternary systems. The phase fields of the different polytypes are generally separated by small two-phase fields. Some general rules for the occurrence of the different Laves phase polytypes are derived from a study of the results of experimental phase diagram investigations of various binary and ternary systems. The solubilities and site occupancies of ternary additions in the different Laves phase polytypes and the mutual miscibility of different binary Laves phases are discussed. The need for careful experimental investigations of phase equilibria is demonstrated. Existing models discussed in the preceding Part I paper are shown to fail to predict the structure and stability of the presented Laves phases in many cases. [Copyright &y& Elsevier]

Single-phase Fe–Al–Ti alloys with the Heusler-type L21 structure and two-phase L21 Fe–Al–Ti alloys with MgZn2-type Laves phase or Mn23Th6-type τ2 phase precipitates were studied with respect to hardness at room temperature, compressive 0.2% yield stress at 20–1100 °C, brittle-to-ductile transition temperature (BDTT), creep resistance at 800 and 1000 °C and oxidation resistance at 20–1000 °C. At high temperatures the L21 Fe–Al–Ti alloys show considerable strength and creep resistance which are superior to other iron aluminide alloys. Alloys with not too high Ti and Al contents exhibit a yield stress anomaly with a maximum at temperatures as high as 750 °C. BDTT ranges between 675 and 900 °C. Oxidation at 900 °C is controlled by parabolic scale growth. [Copyright &y& Elsevier]

Laves phases form the largest group of intermetallic phases. Although they are well known since long, there are still unsolved problems concerning the stability of the respective crystal structures. The Laves phases crystallize with a cubic MgCu2- or a hexagonal MgZn2- or MgNi2-type structure which differ only by the particular stacking of the same four-layered structural units. It is still not possible to predict which of the structure types is the stable one for a Laves phase compound AB2. Phase transformations from a cubic low-temperature structure to a hexagonal high-temperature structure were observed as well as stress-induced transformations from the hexagonal structure to the cubic one. In addition, deviations from the stoichiometric composition were reported to result in a change of the stable polytype in various systems. In this first of two consecutive papers dealing with fundamental aspects of the stability of Laves phases, some factors which are known to affect the occurrence and structure type of Laves phases are discussed and it is shown that, at least up to now, the existing models and calculations are not well suited to give a general description of the stability of Laves phases. [Copyright &y& Elsevier]

Single-phase and two-phase ternary Fe–Al–Mo alloys with Al contents of about 30 or 40 at.% and Mo contents up to 23 at% have been studied with respect to hardness at room temperature, yield stress and fracture strain at room temperature and higher temperatures up to 1000 °C and oxidation at temperatures of 400–1000 °C. The alloys with atomic D03 or B2 order are strengthened by precipitation of the metastable τ2 phase and/or the stable Mo3Al phase, both hard and brittle intermetallic phases, depending on composition and heat treatment. The yield stress as well as the brittle-to-ductile transition temperature increases with increasing Mo content to reach yield stresses up to 1600 MPa with, however, fracture strains below 1% at low temperatures. The observed short-term oxidation is similar to that of other binary and ternary Fe–Al alloys. [Copyright &y& Elsevier]

A series of cylindrical bolts of 80 mm diameter and 115 mm height each weighing about 3.5 kg were produced by hot isostatic pressing (HIP) from pre-alloyed powder of the new intermetallic NiAl–Ta–Cr alloy for high-temperature application with nominal composition 45 Ni, 45 Al, 7.5 Cr and 2.5 Al (at.%). The HIP parameters (temperature, pressure, and time) were chosen according to production scale processing conditions for obtaining specific microstructures. To avoid reactions between the NiAl–Ta–Cr alloy and the Ni capsule, a special coating technique was employed. The microstructure of the compacts was characterised by light optical and scanning electron microscopy and the compositions of the constituent alloy phases were determined by energy dispersive analysis. The temperature dependence of the 0.2% yield stress and the stress and temperature dependence of creep were checked and compared with those of the corresponding laboratory scale material. [Copyright &y& Elsevier]

Several master alloy remelt ingots of about 100 kg each with nominal composition 45 at.% Ni, 45 at.% Al, 7.5 at.% Cr and 2.5 at.% Ta were produced by vacuum induction melting. These ingots were used for a series of investment castings with variation of casting parameters in order to develop and optimise the investment casting process for this new intermetallic NiAl-based alloy. The microstructures of the remelt ingots and of various investment castings were characterised by light optical and scanning electron microscopy (SEM). The compositions of the constituent phases were determined by energy dispersive and wavelength dispersive analysis. The 0.2% yield stress, secondary creep rates and oxidation rates were determined and compared with those of materials produced on laboratory scale. Except of a decreased toughness of the production scale material the properties were otherwise comparable to those of the laboratory scale material. Though properties of the cast alloys are found not to be sensitively affected by impurities such as oxygen, carbon, iron, hafnium and zirconium, silicon was found to promote segregation during casting which is believed to result in embrittlement of the production scale material. Silicon contaminations could be avoided by usage of a ceramic-free cold-wall induction melting aggregate, but due to the coarse resulting microstructures this did not improve toughness of the production scale material. [Copyright &y& Elsevier]

The Al-rich part of the Al–Ti system in the composition range 55–75 at.% Al has been investigated in the temperature range 900–1300 °C. By combining results obtained by metallography, X-ray diffraction (XRD), electron probe microanalysis (EPMA), differential thermo analysis (DTA) and transmission electron microscopy (TEM), the phase equilibria in the respective part of the Al–Ti system have been established. According to these results the existence of the phase Ti1−xAl1+x is ruled out, at least in the investigated temperature range. The phase h-Al2Ti is a metastable phase which forms instantly from TiAl supersaturated with aluminium during cooling but transforms only very slowly into the equilibrium phase r-Al2Ti. h-Al2Ti is frequently observed because the solubility of aluminium in TiAl increases markedly with increasing temperature. Above 1215 °C a continuous homogeneity range exists which extends up to about 71 at.% Al. It is not yet clear whether TiAl is stable up to this Al-content or if there is a second-order transition to the so-called one-dimensional antiphase domain structures (1d-APSs) which are observed in all alloys with at least 68 at.% Al by TEM after cooling. The XRD patterns of the 1d-APSs could be completely indexed by the Al5Ti2-structure. The 1d-APSs/Al5Ti2 are stable down to a temperature of about 980 °C where they disintegrate at a final composition between 70 and 71 at.% Al by eutectoid decomposition: 1d-APSs/Al5Ti2 ↔ r-Al2Ti + Al3Ti. [ABSTRACT FROM AUTHOR]

The cyclic oxidation of Fe–30Al– x Zr and Fe–25Al– x Zr ( x = 0.3–5.2 at.%) has been investigated at 900 °C and 1100 °C in laboratory air. Scales, oxide protrusions and structural changes were analysed by LOM, XRD, SEM and EDS. The oxidation rate increases with increasing Zr content as well as with increasing temperature. Spallation of thin scales formed at 900 °C on the Zr lean alloys is observed, while thicker scales formed on Zr-rich alloys or at 1100 °C show cracking but do not spall. At both temperatures the scales on all alloys consist of Al 2 O 3 , Fe 2 O 3 and ZrO 2 and oxide protrusions penetrate into the samples. These protrusions form by preferential oxidation of Zr rich phases. [ABSTRACT FROM AUTHOR]

Abstract: Isothermal sections of the Co–Al–Nb system at 800, 1000, 1150, 1200, and 1250 °C were experimentally determined by combining results of light-optical as well as scanning electron microscopy, electron-probe microanalysis, and X-ray diffraction measurements with Rietveld analysis of heat-treated alloys and adding some results obtained from solid/liquid diffusion couples. Three polytypes of Laves phases, which are the cubic C15 and the hexagonal C14 and C36 variants, occur as stable phases in the central part of the system. The phase equilibria involving these phases were in the focus of the present study. The composition-dependence of the crystallographic properties of the Laves phases as well as the crystal structure parameters of all other occurring intermetallic phases was investigated. As in case of the binary Co–Nb system, the hexagonal Laves phases C14 and C36 are only stable at off-stoichiometric Nb contents. The preferential site occupations of the Co-, Al-, and Nb-atoms in the hexagonal lattices of the C14 and C36 Laves phase polytypes were determined by Rietveld analyses. For all binary phases except the Nb-rich phase Nb3Al, the solubility for the third element was investigated and the extensions of all phase fields were established. Besides the three Laves phases, the most striking features of the Co–Al–Nb phase diagram are the occurrence of the slowly forming L21-type Heusler phase Co2AlNb and the extended phase field of the μ phase. The existence of a μ′ phase, which was reported in the literature, is not confirmed. [Copyright &y& Elsevier]

Abstract: The mechanical properties of samples taken from different parts of a 650 mm long steam turbine blade forged from Fe–25Al–2Ta (in at.%) by conventional forging on a counterblow hammer were examined. The hardness, brittle-to-ductile transition temperatures (BDTT), the yield stress in compression and in tension, and the creep behaviour were studied and compared with the same material in the as-cast and heat-treated state. Though forging apparently improves the mechanical properties they are still not optimal because of a too large grain size which stems from the insufficiently refined microstructure in the cast precursors. Because some distinct features were observed during creep testing, microstructures of crept samples were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). These investigations revealed that the increased creep resistance below 700 °C is caused by crystallographically oriented sub-micron sized precipitates of a Heusler phase. [Copyright &y& Elsevier]

Abstract: Isothermal sections for 1000 and 1150°C in the Fe–Al–Mo system have been determined experimentally by metallography, X-ray diffraction (XRD) and electron probe microanalysis (EPMA) on equilibrated alloys and diffusion couples. The phase Al8FeMo3 (τ1) was observed at both temperatures. At 1150°C the phases ε∗ and τ2 are found in addition, which both have considerable homogeneity ranges. ε∗ has the hexagonal Al8Cr5-type structure (R-3m, hR26, D810). It can be considered as the ternary derivate of the binary high-temperature phase Al8Fe5 (ε). τ2 has a body-centred cubic W-type structure (Im3m, cI2, A2) with the lattice constant a 0 varying between 0.296 and 0.313nm. Both phases together with the binary phase Al8Fe5 belong to the γ brass family. By differential thermal analysis (DTA) the formation temperatures for ε∗ and τ2 have been established. Besides the occurrence of these phases the strong increase of the solid solubility for Mo in αFe,Al/FeAl with increasing temperature is the main feature within this system. The μ phase Fe7Mo6 is the only other phase which has a marked solid solubility for the third component. From the established phase equilibria a reaction scheme for the temperature range 800–1150°C has been set up. [Copyright &y& Elsevier]

Abstract: The phase diagram of the binary Co–Nb system was redetermined in the whole range of compositions by differential thermal analysis (DTA), electron-probe micro analysis (EPMA), powder X-ray diffraction (XRD), and metallography. Equilibrated alloys of more than 30 different compositions and a series of diffusion couples were used in order to establish the invariant reactions in the system and the homogeneity ranges of all phases. A special feature of the Co–Nb system is the occurrence of three different types of the Laves phase NbCo2, which are a cubic variant (C15) and two different hexagonal variants (C14 and C36). The existence of these three types of the Laves phase was confirmed and their homogeneity ranges were established for the first time. The two hexagonal Laves phase variants are stable only at high temperatures and strongly off-stoichiometric compositions. Two more intermetallic compounds exist in the system: The monoclinic phase Nb2Co7 forms by a peritectoid reaction and has a very small homogeneity range, whereas the μ phase Nb6Co7 in the central part of the system melts congruently and is stable within a broad homogeneity range. [Copyright &y& Elsevier]

Abstract: Phase equilibria in the Fe–Al–Mo system were experimentally determined at 800°C. From metallography, X-ray diffraction and electron probe microanalysis on equilibrated alloys and diffusion couples a complete isothermal section has been established. It is shown that the Laves phase Fe2Mo is a stable phase. The phase Al4Mo, which only becomes stable above 942°C in the binary system, is the only ternary compound found at 800°C. For all binary phases the solid solubility ranges for the third component have been established. The D03/B2 and B2/A2 transition temperatures have been determined for a selected alloy by differential thermal analysis and transmission electron microscopy. The results confirm that the D03/B2 transition temperature substantially increases by the addition of Mo, while the B2/A2 transition temperature is about that for a binary alloy with the same Al content. [Copyright &y& Elsevier]

• Oxide scale formed on Fe-Al protects against aqueous corrosion. • Double-layered Al 2 O 3 scale consists of top Fe-rich equiaxed and bottom pillar-like pure α -alumina grains. • Columnar alumina layer is only formed at high temperatures and after prolonged oxidation. • Incoherent metal-oxide interface is facetted, preventing spallation. The protectiveness of an oxide scale on iron aluminides against aqueous corrosion has been controversially discussed in the literature. For clarification, Fe–25.8 at.% Al was oxidised in air at 1000 °C for 188 h and then immersed in H 2 SO 4 (0.0126 M, pH 1.6). This experiment showed that pre-oxidation can substantially improve the aqueous corrosion behaviour of Fe-Al 31. The present detailed investigation by transmission electron microscopy on the structure and constitution of the oxide scale after aqueous corrosion reveals why the oxide scale improved aqueous corrosion behaviour. During oxidation, a two-layered oxide scale formed. Corrosive attack by the acid is limited to the outer layer, consisting of equiaxed α-Al 2 O 3 and a small amount of spinel. The inner layer of columnar α-Al 2 O 3 grains with few grain boundaries apparently inhibits further ingress of the acid to the scale/metal interface. Faceting of the columnar α-Al 2 O 3 grains at the scale/metal interface explains the good adherence of the oxide scale to the underlying alloy. Differences in oxide scale formation after short-time and prolonged oxidation are likely the reason for the discrepancy in previous observations. [ABSTRACT FROM AUTHOR]

This paper aims to present a methodology to predict the anisotropic and non-linear behaviour of glass fibre reinforced plastics using finite element methods. A material model is implemented in order to remedy the need of multiple material definitions, and to control the local plastic behaviour as a function of the fibre orientation. Injection moulding simulations traditionally provide second order orientation tensors, which are considered together with a homogenization scheme to compute local material properties. However, in the present study, fourth order tensors are used in combination with traditional methods to provide more accurate material properties. The elastic and plastic response of the material model is optimized to fit experimental test data, until simulations and experiments overlap. The proposed material model can support design engineers in making more informed decisions, allowing them to create smarter products without the need of excessive safety factors, leading to reduced component weight and environmental impact. [ABSTRACT FROM AUTHOR]

Ammonia (NH 3 ) is difficult to monitor at atmospheric concentrations due its high solubility and reactivity and the strong spatial and temporal variations of its concentrations. Monitoring is mostly performed using passive samplers or filter packs with daily coverage at best. Only at a few sites ammonia is measured with more expensive wet chemical or spectroscopic measurement techniques. Instruments using an open path show the most potential as these avoid the use of inlets and thus the interactions of NH 3 with tubing, filters, and inlets. Measurements on the vertical distribution of NH 3 are even scarcer, with only a few available airborne and tower measurements. Satellite observations of NH 3 show potential to be used for real-time monitoring as these have global coverage often with daily overpasses. Unfortunately, validation of satellite NH 3 products representing the total atmospheric column with ground based instruments measuring in situ NH 3 has been troublesome due to a lack of knowledge about the vertical distribution. Validation with FTIR instruments has shown potential but has been performed for only a limited number of stations. In this study we report on measurements performed during the Measuring atmospheric Ammonia with Remote Sensing (MARS) field campaign at Cabauw, the Netherlands. The aim of the campaign was to improve the general understanding of the vertical distribution of NH 3 . An approach was taken using four mini-DOAS instruments installed in the meteorological tower at Cabauw, supplemented by measurements with a MARGA and a mobile FTIR instrument. The measurements between May and October 2014 showed large variations in the concentrations and maximum concentrations reached up to 240 μg m −3 . The lower three mini-DOAS and MARGA measurements showed large differences on an hourly basis, which were shown to originate from multiple measurement artefacts of the MARGA. The mini-DOAS concentrations varied sharply between the different levels with the lower three instruments showing maxima at night while the mini-DOAS at 160 m in the tower showed maxima during the day. The study shows that the daytime boundary layer is well-mixed with only small gradients between concentrations measured at various heights. Differences were found in the origin of the NH 3 with the instrument at 20 m showing higher concentrations with transport from the north, where the largest nearby sources are located, while the instrument at 160 m showed the highest concentrations coming from the east which shows a more regional influence. The measurement campaign data is freely available for model and satellite validation studies. [ABSTRACT FROM AUTHOR]

The composition of the metastable L2 1 Heusler phase in Fe 2 AlX with (X = Nb, Ta) alloys has been determined by atom probe tomography (APT). It was found that the composition of L2 1 is off-stoichiometric in both systems, however closer to the stoichiometric composition in the Fe-Al-Ta than in the Fe-Al-Nb(-B) alloy. L2 1 dissolves faster and therefore the formation of the stable C14 Laves phase proceeds quicker in the Fe-Al-Nb(-B) alloy. Doping with boron does not lead to the formation of borides and only a slight enrichment of boron in the Fe-Al matrix at the grain boundary, which is covered with C14 precipitates is observed. [Display omitted] [ABSTRACT FROM AUTHOR]

We study an Fe–18Al (at.%) alloy after various thermal treatments at different times (24–336 h) and temperatures (250–1100 °C) to determine the nature of the so-called ‘komplex’ phase state (or “K-state”), which is common to other alloy systems having compositions at the boundaries of known order-disorder transitions and is characterised by heterogeneous short-range-ordering (SRO). This has been done by direct observation using atom probe tomography (APT), which reveals that nano-sized, ordered regions/particles do not exist. Also, by employing shell-based analysis of the three-dimensional atomic positions, we have determined chemically sensitive, generalised multicomponent short-range order (GM-SRO) parameters, which are compared with published pairwise SRO parameters derived from bulk, volume-averaged measurement techniques (e.g. X-ray and neutron scattering, Mössbauer spectroscopy) and combined ab-initio and Monte Carlo simulations. This analysis procedure has general relevance for other alloy systems where quantitative chemical-structure evaluation of local atomic environments is required to understand ordering and partial ordering phenomena that affect physical and mechanical properties. [ABSTRACT FROM AUTHOR]

Abstract: The corrosion behaviour of binary Fe–Al alloys with Al contents ranging from 10 to 45 at.% Al and of ternary Fe–Al–Ti alloys with Al contents of about 25 at.% Al has been investigated in steam. No pre-oxidation has been applied. Saturated water vapour produced by a “steam generator” was passed over the samples in a quartz tube. The tests were conducted at 700 °C for 672 h without employing a carrier gas. The weight changes of the samples were determined after the experiments, and the formed scales were characterised by light optical microscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results for the different alloys vary quite markedly. Corrosion resistance for the binary alloys improves with increasing Al content, while the corrosion attack of the Fe–Al–Ti alloys is more severe. [Copyright &y& Elsevier]

Abstract: In this investigation phase relations in the Fe–Ni–Ti system were studied and two isothermal sections at 800°C and 1000°C as well as a revised liquidus projection were established. Microstructural characterisation of the as-cast alloys and of samples equilibrated at 800 and 1000°C was performed by scanning electron microscopy (SEM), chemical compositions of the phases were analysed by electron probe microanalysis (EPMA), and liquidus temperatures were examined by differential thermal analysis (DTA). The experimental results clarify some uncertainties concerning the melting behaviour and the solid-state phase equilibria between the phases (Ni,Fe)Ti2, (Fe,Ni)Ti and β-Ti. The present data also confirm that the solid solubility of Ti in γ-(Fe,Ni) varies in dependence on the Fe:Ni ratio and decreases with decreasing temperature. The liquidus projection as well as the reaction scheme in the Ti-lean part are modified because two ternaries eutectic E 1: L↔γ-(Fe,Ni)+Fe2Ti+Ni3Ti and E 2: L↔Fe2Ti+Ni3Ti+(Fe,Ni)Ti are found at 1108 and 1099°C, respectively. [Copyright &y& Elsevier]

Abstract: The crystal structure of the high-temperature ɛ phase of the Fe–Al system has been determined by in-situ high-temperature neutron diffraction for the first time and the crystallographic parameters have been established by Rietveld refinement of the data. The ɛ phase was found to have a body-centered cubic structure of the Hume-Rothery Cu5Zn8-type (space group I 3m (No. 217), Z =4, Pearson symbol cI52, Strukturbericht designation D82). Accordingly, the ε phase has the formula Fe5Al8. Its lattice parameter is a =8.9757(2) Å at 1120°C, which is 3.02 times that of cubic FeAl (B2) at the same temperature. All fractional atomic coordinates, site occupation factors and interatomic distances were determined and it was examined how this phase can meet the rules for Hume-Rothery-type phases. [Copyright &y& Elsevier]

Abstract: Single-phase alloys of the monoclinic intermetallic phase Nb2Co7 were investigated with respect to their mechanical behaviour. The material can be strongly deformed at room temperature by hammering without shattering or fracturing and it can be strained in compression to at least 5% without fracture. At the same time, Nb2Co7 behaves like a brittle material when tested under bending or tensile load. The mechanical properties of this phase were systematically studied by microhardness, compression, tensile and bending tests and the microstructure was analysed by light-optical and scanning electron microscopy before and after testing. [Copyright &y& Elsevier]

Abstract: The brittle-to-ductile transition temperature (BDTT) of binary Fe–Al alloys with between 9.6 and 45at.% Al was investigated in the as-cast state by four-point bending tests. An increase of the BDTT was observed with increasing aluminium content between 9.6 and 19.8at.%. Up to 41.3at.%, the BDTT did not change significantly. A sharp increase of the BDTT occurred between 41.3 and 45at.% Al. Transgranular cleavage was observed at a composition of 25at.% Al, mixed-mode fracture between 39.6 and 41.3at.% Al and intergranular fracture at 45at.% Al. The results indicate that the increase in BDTT is correlated with the transition from mixed-mode to intergranular fracture. [Copyright &y& Elsevier]