Alloys created between immiscible elements

Highly supersaturated nanocrystalline FexCu100−x alloys (10≤x≤95) have been prepared by mechanical alloying of elemental crystalline powders The development of the microstructure is investigated by x‐ray diffraction, differential scanning calorimetry, and transmission electron microscopy The results are compared with data for ball‐milled elemental Fe and Cu powders, samples prepared by inert gas condensation, and sputtered films The deformation during milling reduces the grain size of the alloys to 6–20 nm The final grain size of the powders depends on the composition of the material Single‐phase fcc alloys with x≤60 and single‐phase bcc alloys with x≥80 are formed even though the Fe‐Cu system exhibits vanishingly small solid solubilities under equilibrium conditions For 60≤x≤80, fcc and bcc solid solutions coexist The alloy formation is discussed with respect to the thermodynamic conditions of the material The role of the large volume fraction of grain boundaries between the nanometer‐sized cryst

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Mechanically driven alloying and grain size changes in nanocrystalline Fe-Cu powders

X-ray diffraction, transmission electron microscopy, and differential scanning calorimetry were used to study the thermal stability of highly supersaturated nanocrystalline FexCu100−x alloys (10 ~80. For 60<=x<=80 fcc and bcc phases coexist. Heating to elevated temperatures leads to structural relaxation, phase separation, and grain growth of the metastable nanocrystalline solid solutions. Single-phase fcc and bcc alloys undergo significant strain release but no appreciable grain growth prior to phase separation. After phase separation pronounced grain growth sets in. In contrast, samples in the two-phase region show some grain growth and significant chemical redistribution even at low temperatures. The phase separation of single-phase fcc and bcc alloys proceeds via different mechanisms: fcc solid solutions decompose by forming small Fe precipitates, while demixing in bcc alloys starts by segregation of Cu atoms to bcc grain boundaries before nucleation of Cu precipitates. These results show that the stability and grain growth behavior of nanocrystalline alloys is strongly affected by the microstructure of the material.

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Thermal stability and grain growth behavior of mechanically alloyed nanocrystalline Fe-Cu alloys

The size, number density and compositions of ultrafine copper–manganese precipitates that form in Fe–0.80at.% Cu and Fe–0.78at.% Cu–1.05at.% Mn model alloys that were neutron irradiated to a fluence of ∼1×1023 nm−2 (E>1 MeV) at 288 °C have been estimated by atom probe tomography and small-angle neutron scattering (SANS) experiments. The number density of precipitates was approximately an order of magnitude higher in the Fe–Cu–Mn alloy than in the Fe–Cu alloy. A direct comparison of the microstructural parameters estimated by each technique revealed good agreement between the radii of gyration and the number densities. However, the copper content in precipitates inferred from SANS was significantly higher than estimated from the atom probe results.

Precipitation in neutron-irradiated Fe-Cu and Fe-Cu-Mn model alloys : a comparison of APT and SANS data

Characterization of neutron-irradiated ferritic model alloys and a RPV steel from combined APT, SANS, TEM and PAS analyses

High concentration Fe 1- x Cu x alloys have been obtained by rf sputtering technique and investigated by X-ray diffraction and magnetization measurements. The bcc phase is extended over the region with x =0–0.4, while the fcc phase with x =0.6–1.0. For x =0.4–0.6, we have the mixed phase of bcc and fcc. The lattice constant of bcc phase increases slightly and that of fcc phase decreases with increasing x . In the bcc alloys, the average magnetic moment decreases with increasing x and deviates upwards from the simple dilution law. In the fcc alloys, the magnetic moment also decreases with increasing x but it deviates downwards from the simple dilution law. The Curie temperature, T c , of the Fe 1- x Cu x alloys decreases abruptly with increasing x : T c is higher than 750 K for the bcc alloys, while it is lower than 320 K for the fcc alloys and become 0 K at about x =0.92.

Magnetic properties of metastable bcc and fcc Fe-Cu alloys produced by vapor quenching

On a obtenu experimentalement les spectres Mossbauer a 4,2 et 290 K des alliages Fe 1−x Cu x pulverises. Etude detaillee du spectre et en particulier d'un sextuplet ferromagnetique en fonction de la composition. Le champ hyperfin est plus faible que celui des alliages cubiques centres et diminue graduellement avec x

Tsutomu Yoshitake

Papers

Magnetic properties of metastable bcc and fcc Fe-Cu alloys produced by vapor quenching

Mössbauer Effect of Metastable bcc and fcc Fe–Cu Alloys Produced by Vapor Quenching