On the role of martensite in the formation of microstructures in heat resistant 9 to 12% chromium steels

The present work uses transmission electron microscopy to study the formation of the microstructure of a 12% chromium tempered martensite ferritic steel. The main emphasis placed on the difference between a martensitic material state and the tempered material state. Tempering results in a decrease of dislocation density and in an increase of the width of elongated ferritic micro grains (as opposed to martensitic laths). Adjacent micro grains in the tempered material state are separated by high and low angle boundaries. High angle boundaries are of {110}- type

Laser additive manufacturing of iron aluminides strengthened by ordering, borides or coherent Heusler phase

Laser Additive Manufacturing (LAM) is a near-net-shape processing technology well-suited for the production of parts from intermetallic alloys. Three different iron aluminide alloys have been processed by Selective Laser Melting (SLM) and Laser Metal Deposition (LMD). The alloys selected for LAM represent three different strategies for strengthening iron aluminides at high temperatures: Increase of the ordering temperature D03 ↔ B2 (Fe–30Al–10Ti; all compositions in at.%), precipitation of borides (Fe–30Al–5Ti–0.7B) and generation of coherent A2 + L21 microstructures (Fe–22Al–5Ti). It is shown that all three alloying strategies established from as-cast alloys can also be realised through both LAM processes, generating defect free and dense (> 99.5%) samples. Yield stress and compressive creep strength also match that of the as-cast alloys above 600 °C, while at lower temperatures in some cases higher yield stresses are observed. In addition, the yield stress below 600 °C may also depend on the building direction and may change after a heat treatment. No general improvement of ductility is observed, specifically in case of Fe–30Al–10Ti, where the grain size in the LAM processed samples is one magnitude lower than in the as-cast alloy. However, depending on building direction and subsequent heat treatment some samples become ductile at quite low temperatures, which at least in some cases may be explained by the internal stresses measured by XRD

Characterization of U-based thin films: the UFe2+xcase

We have characterized UFe2+x films prepared by sputter deposition onto fused silica (SiO2) and Si(111) substrates with the film thickness ranging from 75 nm to 900 nm. The Xray diffraction results showed an amorphous character of the deposited material. Some of the films showed in addition a pattern of highly textured cubic Laves phase. Rutherford Backscattering Spectroscopy with 2 MeV He+ ions has been used to determine the composition, thickness and concentration depth profile of the films. A large ageing affect was observed within 1 month after that the films were exposed to air. Magnetic measurements revealed TC increasing with relative Fe concentration and reaching approx. 450 K in UFe3.0

5f Magnetism---Specific Features And Boundaries

Magnetism of light actinides exhibits fascinating and potentially useful features. One of them is a giant anisotropy of the two‐ion type, apparent mostly in U‐based systems. Here we demonstrate on the example of U2Ni2Sn and its hydride the anisotropy switches over the direction of U moments on a very fine scale. The study of amorphous sputter deposited UFex films reveals how the Curie temperature can be tuned so as to exceed the room temperature

Characterization of U-based Thin Films - the UFe2+x Case

We have characterized UFe2+x films prepared by sputter deposition onto fused silica (SiO2) and Si(111) substrates with the film thickness ranging from 75 nm to 900 nm. The X-ray diffraction results showed an amorphous character of the deposited material. Some of the films showed in addition a pattern of highly textured cubic Laves phase. Rutherford Backscattering Spectroscopy with 2 MeV He+ ions has been used to determine the composition, thickness and concentration depth profile of the films. A large ageing affect was observed within 1 month after that the films were exposed to air. Magnetic measurements revealed TC increasing with relative Fe concentration and reaching approx. 450 K in UFe3.0.JRC.E.6-Actinides researc

Uranium compounds prepared by sputter deposition: UFe2+x

UFe2 is one of rare examples of combination of 3d and 5f magnetism in a compound with relatively high TC = 162 K. U-excess is known to reduce the TC value markedly. To prepare the Laves phase with an Fe excess is much more difficult. It can be achieved by sputter deposition, but the structure becomes amorphous. TC can increase at least to 240 K (for UFe4), but the segregation of α-Fe cannot be avoided for very high Fe concentrations

Magnetic evaluation of microstructure changes in 9Cr-1Mo and 2.25Cr-1Mo steels using electromagnetic sensors

This paper presents results from a multi-frequency electromagnetic sensor used to evaluate the microstructural changes in 9Cr-1Mo and 2.25Cr-1Mo power generation steels after tempering and elevated temperature service exposure. Electromagnetic sensors detect microstructural changes in steels due to changes in the relative permeability and resistivity. It was found that the low frequency inductance value is particularly sensitive to the different relative permeability values of both steels in the different microstructural conditions. The changes in relative permeability have been quantitatively correlated with the microstructural changes due to tempering and long-term thermal exposure, in particular to changes in martensitic/bainitic lath size and number density of carbide precipitates that determine the mean free path to reversible domain wall motion. The role of these microstructural features on pinning of magnetic domain wall motion is discussed