M. Magnani

Investigation of Mg2Si precipitation in an Al-Mg-Si alloy by small angle neutron scattering

Abstract Small angle neutron scattering (SANS) was used to investigate the precipitation process in a high purity Al-Mg (0.72%)-Si(0.34%) alloy. In particular, the Mg 2 Si precipitation was studied as a function of ageing temperature on polycrystalline samples. The measurements were carried out at the D17 facility of the ILL in Grenoble. Coherent scattering cross-section curves were obtained for the different aged samples from which the size distribution functions of coherent and incoherent particles were determined. The SANS results are compared and discussed with reference to TEM observation and resistivity measurements.

A microstructural comparison of two nuclear-grade martensitic steels using small-angle neutron scattering

Abstract Results are presented of a small-angle neutron scattering (SANS) study on two 10–13% Cr martensitic stainless steels of interest for nuclear applications, viz. DIN 1.4914 (MANET specification, for fusion reactors) and AISI 410. The investigation has focussed principally on microstructural effects associated with the differences in chromium content between the two alloys. The size distribution functions determined from nuclear and magnetic SANS components for the two steels given identical heat treatments are in accord with an interpretation based on the presence of ∼ 1 nm size CCr aggregates in the microstructure. Much larger (∼ 10 nm) scattering inhomogeneities with different magnetic contrast are also present and tentatively identified as carbides.

Non-Destructive Investigation of Microporosity in Marbles by means of Small Angle Neutron Scattering

Abstract Small-angle neutron scattering (SANS) measurements have been carried out on different marble and limestone samples, of relevance to cultural heritage safeguard, to investigate the micropore distribution in the size range between 10 and 1000 A. Different varieties of marbles have been studied using a CaCO 3 single crystal, pore-free, as a reference. A series of red scaglia limestone samples has also been tested obtaining for this material, very reproducible results. Namely identical SANS cross-sections are found for specimens issued from a modern quarry and for samples issued from a historical building. Furthermore, the micropore volume distribution functions obtained by Fourier transformation of the SANS data are in accordance with porosimetry results for pore sizes larger than approximately 500 A. The results of SANS measurements carried out to try and distinguish close and open microporosity are also reported.

Particle size and optical performances of photoluminescent laser synthesized Si nanopowders

Abstract Laser synthesized Si nanopowders, developed for application in optoelectronics, have been investigated using small-angle neutron scattering (SANS) to characterize how the particle size distribution function evolves by acting on reaction parameters. In this work a discussion on SANS results, which are compared with information available from transmission electron microscopy (TEM) observations and Brunauer–Emmett–Teller (BET) measurements, is reported.

Study of He-bubble growth in α-particle implanted F82H-mod martensitic steel

This paper presents the results of a small-angle neutron scattering (SANS) study of He-bubble growth in martensitic steel F82H-mod. The investigated samples had been homogeneously implanted with 400 appm He at 250°C, then submitted to 2 h annealings up to 975°C, together with a non-implanted sample of the same material (one for each temperature) serving as a reference to isolate the SANS signal arising from the He-bubbles. An as-implanted sample was also investigated together with its thermal reference. The He-bubble volume distributions, obtained from the SANS data and discussed with reference to uncertainties arising from background subtraction, show that the uniform distribution of the as-implanted sample, with bubbles approximately 15 A in size, evolves during high temperature annealing into a bimodal one with a secondary population of bubbles as large as 100 A approximately.

Small angle neutron scattering investigation of the ageing process in Al-Mg-Si alloy

SANS measurements are presented to investigate the ageing process of a polycrystalline Al-Mg-Si alloy a 210°C. The growth of needle-shaped precipitates as a function of ageing time is observed, in accordance with TEM observations. The precipitated fraction estimated from the size distribution function agrees with resistivity measurements previously performed on the same alloy. Bidimensional scattering profiles are also given in the case of a single crystal; the data analysis is in progress.

Microstructural characterisation of F82H-mod. steel using small-angle neutron scattering

Small-angle neutron scattering (SANS) measurements have been carried out on samples of F82H-mod. martensitic steel submitted to different treatments: (a) hardening, (b) tempering and (c) ageing. Size distribution functions referable to the precipitates, formed during the different treatments are obtained both for nuclear and magnetic SANS components. The results, discussed making reference to transmission electron microscopy (TEM) observations and microhardness measurements, show that while samples of groups (a) and (c) exhibit a stable microstructure, marked differences are detected varying the tempering temperature, especially at 550°C (where a fine precipitation is observed) and for temperatures higher than 850°C (formation of delta ferrite).

Microstructural evolution, under tempering at 700°C, in a steel for fusion reactors

Abstract This work presents the results of SANS measurements carried out on samples of modified martensitic steel DIN 1.4914 (MANET-type) submitted to tempering at 700°C for times up to 20 h. The size distribution functions determined from the nuclear and from the magnetic SANS components show the presence of: (1) very large ( > 100 A ) particles with strong magnetic contrast to be possibly identified as M23C6 precipitates (non-magnetic, imbedded in a magnetic matrix); (2) much finer scattering centers ( ∼10 A ) with different magnetic constrast to be identified with CCr aggregates. The microstructural evolution under tempering is discussed in the light of the SANS results.

Topography of a IN738 superalloy turbine blade by small-angle neutron scattering

The size distribution of microstructural inhomogeneities in a turbine blade sample, not operated and built of IN738 Ni- based superalloy, has been investigated by Small-Angle Neutron Scattering. Data analysis has ben performed taking into account multiple scattering, that is not negligible due to the large thickness of the sample. Results show the presence of inhomogeneities with dimensions compatible with (gamma) phase particles, already observed by scanning and transmission electron microscopy.