Iron-manganese Alloys Research Articles

Structure and features of failure of powder metallurgy sintered high-manganese alloys

1. Powder metallurgy alloys produced from carbonyl iron possess higher structural and chemical homogeneity than similar alloys produced from electrolytic iron. This may be explained by the higher degree of mixing with the use of carbonyl iron and the more complete occurrence of the diffusion processes in sintering, which is related to the dispersion of the powder particles. 2. The relationship of the character of fracture in the alloys to manganese content for the carbonyl iron-base alloys is close to the similar relationship for cast alloys. 3. The presence in the powder metallurgy materials of a critical porosity above which the rules of the mechanics of a continuum do not act was established. The critical porosity of carbonyl iron-base sintered iron-manganese alloys is about 15% and of electrolytic ironbase ones less than 9%. With a porosity below the critical the character of fracture is determined by the properties of the solid solution itself and the ductile-to-brittle transition temperature while with a porosity above the critical by the number of diffusion contacts (pseudoductility). 4. The advantages revealed of carbonyl iron-base alloys make it possible to recommend this powder for production of sintered iron-manganese alloys.

Cold shortness and nature of failure of iron-manganese powder alloys

The level and nature of variation of impact toughness in the iron-manganese powder alloys are similar to the vacuum-melted cast alloys. The lowest cold brittleness threshold was recorded for the alloys with 20–23% Mn (determined at −253°C) containing the maximum amount of ɛ-martensite and positioned at the boundary of the α + ɛ + γ and ɛ + γ regions. Brittle fracture in these alloys takes place by the intercrystalline mechanism, and the inclusions, depending on their composition, size, and distribution, can both support crack propagation and delay this process. The possible mechanisms of failure of the powder materials are proposed on the basis of the literature data and own experimental investigations.

Morphological development of oxide-sulfide scales on iron and iron-manganese alloys

Pure iron and alloys containing 2, 15, 25, and 50 wt. % manganese have been reacted at 1073 K in controlled gas atmospheres of SO2-CO2-CO-N2.Equilibrium gas compositions were such that (1) FeS was stable but not FeO, or (2) both FeS and FeO were stable, or (3) FeO was stable but not FeS; in all cases, both MnS and MnO were stable. Under all reaction conditions, pure iron corroded to produce both sulfide and oxide. The resultant scale morphologies were consistent with local solid-gas equilibrium for the case in which both oxide and sulfide were stable but in the other cases indicated that equilibrium was not achieved and that direct reaction with SO2(g) was responsible for corrosion. Additions of manganese did not greatly alter the scale morphologies. Under reaction conditions that were oxidizing and sulfidizing, very high levels of manganese were required to reduce the corrosion rate. On the other hand, relatively low levels had a beneficial effect both when FeO but not FeS was thermodynamically stable and similarly when FeS but not FeO was stable.

Enthalpies of mixing in the iron-manganese system by direct reaction calorimetry

Integral enthalpies of mixing of solid iron—manganese alloys have been obtained at 1443K, 1073K and 873K using a modified Dench-type calorimeter. The modifications in calorimetric technique required to cope with the high volatility of manganese are described. Results are presented and discussed.

Mechanical properties and the fine structure of powdered iron-manganese alloys

Mechanical properties and the fine structure of powdered iron-manganese alloys

The effect of the amount of-phase on the vibration absorbing properties of powdered iron-manganese alloy

A correlation was established between the content of ɛ-phase in the structure of the alloy Fe-Mn and its vibration absorbing properties. An increase of the amount of ɛ-martensite to 50–60% leads to an improvement of the vibration absorbing properties; when the content of ɛ-phase is further increased, the vibration absorbing properties deteriorate. To ensure maximal vibration absorption, the alloy has to contain 50–60% ɛ-phase. It was also cleared up what effect some heat treatment parameters have on the amount of ɛ-phase contained in the alloy.

Mechanical properties of iron-manganese alloys of high and commercial purities

The authors investigate Fe-Mn alloys with the purpose to study the mechanical properties within the same concentration range (4-54% Mn) as a function of the purity of melting and the type of the crystal lattice. These Fe-Mn alloys could possibly be used in a definite concentration range as a new class of nickel-free cryogenic materials. Two groups of iron-manganese alloys of high and commercial purities were taken for this investigation; their chemical analyses are presented. The results obtained in an investigation of the fine-structure Fe-Mn alloys by diffraction electron microscopy methods determined the extent of the effect of packing defects and twins on the level of mechanical properties caused by the effect of phase transformation.

Nickel-free iron-manganese alloys

1. Melt purity has a marked effect on the level of mechanical properties for Fe−Mn alloys and the nature of their change with an increase in manganese concentration. 2. For high-purity alloys strength properties increase markedly in the two-phase (e+γ)-region. Alloy with 21–24% Mn has the maximum strength (σf = MPa; σ0.2 = 4.50 MPa). 3. At the boundary of the (e+γ)-and γ-regions for high-purity alloys "boundary" or concentration superplasticity is observed; a reduction in test temperature to −196°C is accompanied by an increase in relative elongation. 4. For industrial purity alloys strength properties decrease gradually with a changeover from α- to e- and γ-solid solutions. Strength and ductility properties of these alloys are insensitive to the position of the (e+γ)- and γ-region boundary. 5. With an increase in melt purity reserve ductility for Fe−Mn alloys increases, and this has been established by fractographic study of the nature of their failure.

The martensitic transformation in cold-worked Fe-Mn alloys studied by M�ssbauer spectroscopy

The effect of cold-working on 16, 23 and 30 at% Mn iron-manganese alloys (C<0.05 at%) has been examined using Mossbauer spectroscopy and X-ray diffractometry. The induced martensitic transformation γ→e, α′ depends on the composition and on the initial structure. It is found that the γ→α′ transformation in presence of the e phase occurs only at high deformations.

The oxidation of binary iron-manganese alloys

Oxide scales formed on iron-manganese alloys are generally considered to be similar to those formed on the parent metals. Metallographic examination is used in conjunction with EMPA, XRD, and X-ray imaging to reveal the presence of the additional phases Mn2O3 and Mn3O4 in the scales formed on binary alloys containing up to 40% manganese at 700 and 800°C in 200 Torr oxygen. A mechanism is proposed to explain the apparent change in growth from iron-rich to manganese-rich scales during oxidation of Fe-40Mn at 800°C.

Effects of magnetic and structural changes on elastic moduli of iron-manganese alloys

Abstract Measurements of ultrasonic wave velocities have been carried out on a sample of Fe-22–6.at.° Mn between 300 and 500 K. Above 470 K the sample is a single crystal of f.c.c. structure, but below 350 K it contains platelets of h.c.p. martensite within the matrix single crystal. The longitudinal wave velocities measured in the [110], [001] and [111] directions show considerable hysteresis arising from the h.c.p. b.c.c. structural transition near 450 K with increasing temperature and from the reverse transition below 390 K. In the [110] and [001] directions the longitudinal wave velocity shows a smoothed step-like anomaly at the Neel point TN≈ 370 K of the f.c.c. crystal. These measurements, together with the measurements of shear wave velocity in the [110] direction, indicate that there is a softening of about 60° in the shear modulus C = (c11 — cl2) /2 arising from antiferromagnetism, but no detectable anomalies in the shear modulus C = c44 nor in the bulk modulus .B = (c11 + 2c12) /3. A comparison ...

Effect of Temperature on the Corrosion of 70/30 Copper–Nickel in Sea Water

This paper presents the results of experiments to investigate the effect of temperatureon the films found on 70/30 copper–nickel. The results show that the potential of 70/30 copper–nickel and 66/30/2/2 copper–nickel explain the poor resistance to impingement attack of this alloy at low temperatures, observed greater than 10°c. At temperatures below 10°c the potential remained more or less constant at about −200 mV (SeE) for the duration of the test. The electropositive shift in potential was associated with an enrichment of iron in thefilm on the 70/30 copper–nickel alloy. No clear changes infilm composition with temperature could be determined for the 66/30/2/2 copper–nickel–iron–manganese alloy. No changes in potential were observed for 90/10 copper–nickel, even after extended testing. The results for 70/30 copper–nickel explain the poor resistance to impingement attack of this alloy at low temperatures, observed in previous research at BNF.

A Mössbauer spectroscopic study of sulphidation of iron-manganese alloys

Mössbauer absorption spectra were measured for sulphides obtained from iron-manganese alloys at 1000°C under 3.5 × 10 −7-1 atm. sulphur pressures. Depending on the sulphidation conditions, FeS 2, Fe 1- x S, stoichiometric FeS and MnS type sulphides were identified. For the Fe 1- x S phase Fe(II) ions with and without first neighbour vacancies were distinguished. From the dependence of the isomer shift and the relative intensity of the absorption it was possible to construct a Maurer equilibrium diagram for the FeS-MnS quasi binary system. An explanation for the role of manganese in sulphidation resistance is also given.

Sound radiation efficiency of metals

The purpose of this investigation was to determine the influence of controllable metallurgical properties on the radiated sound after impact using iron—manganese alloys and some forge hammer construction metals. The effect of metal properties on sound radiation can be characterized by the rate of attenuation of the sound, dp. For rectangular plate linear dimensions a and b. dp = 60[(ma)2 + (nb)2]Q−1(σ0Eh3rs)1/2 × {4.8498[σ0(1 − μ2)mprs]1/2 − 0.3536[(ma)2 + (nb)2] × Q−1(πEh3ms)1/2}−1 + C, dB/s, where E is elastic modulus, μ is Poisson's ratio, Q−1 is internal friction, σ0 is ultimate strength, p is the mass density, m, n is a mode number, h is the thickness of the plate, rs is the radius of the striker, ms is the mass of the striker. C is a constant accounting for the changes due to environmental scattering and absorption by the surfaces. The attenuation rate of sound radiation has been shown to be affected by the mechanical properties of the metal and geometry of solid collision. The mechanical properties can be modified by controlling the heat-treatment and the chemical composition of the metal, as well as its mechanical working.

Brittleness of ?, ?, and ? solid solutions of Fe-Mn alloys

1. Iron-manganese alloys with ferritic and martensitic structures have high ductile-brittle transition temperatures and transcrystalline brittle fractures. 2. Alloys with e martensite (α+e+γ and e+γ) are characterized by a lower ductile-brittle temperature (−20 to −80°) and higher fracture toughness than α alloys; the ductile fractures are dimpled and the brittle fractures are intercrystalline. 3. A clear ductile-brittle transition is observed in γ alloys; the ductile dimpled fracture changes to brittle intergranular fracture in a relatively narrow temperature range. 4. Manganese raises the ductile-brittle temperature of γ alloys in contrast to α and e alloys, for which the transition temperature drops with increasing manganese concentrations. 5. Brittleness of austenitic Fe-Mn alloys is not associated with structural transformations: The transition to the brittle condition may be due to changes in electron structure.

Environmental effects in iron-manganese alloys

The diffuse scattering cross-sections of polarized neutrons of wavelength 4.73 Å from three samples of disordered iron-manganese alloys, containing 3.15, 5.89 and 8.83 at.% of manganese, have been measured at room temperature The magnetic moment on the manganese atoms is evaluated at 0.8 μ B and the modifications of the moments on the neighbouring iron atoms have been calculated.

High-temperature study of the magnetic susceptibility of iron-manganese alloys

Using the Faraday method, the paramagnetic susceptibility of Fe-Mn alloys is studied over very substantial ranges of temperature and concentration (room temperature to 1800°C and 0–80% Mn). The results are interpreted within the framework of the zone (energy-band) model, allowing for the resonance scattering of the collectivized d electrons at the ions of the transition metal.

Structure and properties of iron-manganese alloys

Structure and properties of iron-manganese alloys

Iron–Manganese–Nitrogen Ferrite: The Activity of Nitrogen and the Solubility of Manganese Nitrides

Iron–manganese alloys containing 0–4 %Mn have been nitrided in the range 450–550°C. The effect of manganese on the activity of nitrogen was found to be given byThe precipitates in equilibrium with the various alloys at 550°C were: 0·53%Mn, Fe4N; 0·785–1·18%Mn, η-Mn3N2; 2·15 %Mn, ζ-Mn5N2. The solubility of η-Mn3N2 was determined approximately.

Oxidation of Iron–Manganese–Sulphur Alloys. Part I: External and Internal Oxidation of Iron-Manganese Alloys

Oxidation of Iron–Manganese–Sulphur Alloys. Part I: External and Internal Oxidation of Iron-Manganese Alloys