Warm forming of high strength Aluminum alloys is a promising process for avoiding the low formability intrinsic to these precipitation-strengthened materials. However, during a process combining temperature and strain, precipitates undergo complex a dynamic evolution due to the plastic strain, which is not quantitatively understood in terms of influence of initial temper, strain, strain rate and temperature. Deformation can both induce precipitate dissolution due to shearing or accelerate the precipitation kinetics by producing excess vacancies. In this work, Small Angle X-ray Scattering in situ tensile tests have been performed on aged Al-Zn-Mg-Cu samples over a wide parameter space to understand the influence of deformation on precipitation. A competition between dynamic dissolution and dynamic precipitation has been highlighted, which depends on the temperature and the strain rate. Dynamic dissolution mainly depends on strain. Conversely, dynamic precipitation is a diffusive process, and therefore depends on the deformation temperature and the deformation duration. This competition has been confirmed by selected atom probe tomography observations.

Precipitation hardening alloys are increasingly used for vehicle lightweighting. A critical property for these applications, formability, is poor in these high strength alloys, which has led to the development of warm forming processes. In these conditions, dynamic interactions exist between plastic deformation and precipitation, which are not yet fully understood. This work investigates the precipitation kinetics in an Al-Cu alloy, the AA2219 alloy, comparatively during aging at 200 degrees C without deformation, with a pre-deformation prior to aging and with a warm deformation during aging. The in-situ Small-Angle X-ray scattering measurements demonstrate that the precipitation kinetics is accelerated by plastic deformation, all the more when applied at the aging temperature. Transmission electron microscopy shows that static and dynamic interactions result in qualitatively similar microstructures, showing that the nucleation of precipitates is similar after pre-deformation or during dynamic precipitation. The enhanced kinetics in dynamic conditions is related to the diffusion acceleration caused by the excess vacancies production during plastic deformation.

MoS2 active phase found in CoMoP/Al2O3 catalysts can be described as a multiscale Mo organization with MoS2 slabs and slab aggregates. The aim of this paper is to understand how such multiscale organization is formed from the oxide initial state. Sulfidation of two catalysts impregnated with 26 %wt MoO3, one dried, the other one freeze‐dried, has been followed ex situ by EXAFS, XPS and ASAXS. Initially, two types of Mo oxide precursors are present on the support such as dispersed MoO42‐ species and oxide aggregates constituted of heteropolyanions, polymolybdates and H6AlMo6O246‐ Anderson HPA (AlMo6). A 3‐step genesis is highlighted during the sulfidation regardless of the catalyst: i) AlMo6 depolymerizes into MoO42‐ entities from RT to 240°C, ii) MoO42‐ is preferentially sulfided compared to other entities and slab aggregates sulfidation is delayed in the presence of important MoO42‐ amount, iii) restructuration of the slabs within slab aggregates occurs during sulfidation of the latter and leads to their expansion. The drying method (drying or freeze‐drying) influences the kinetics of this 3‐steps genesis. As the freeze‐dried catalyst presents more AlMo6 and thus MoO42‐, a late restructuration within aggregates leads to larger ones. Initial speciation of the catalysts determines the final Mo multiscale organization.

Material sustainability requires energy-efficient and rapid strengthening processes. In alloys, strengthening through diffusion-driven precipitation is limited by the low vacancy concentration, with fewer than one vacancy per 100 billion lattice sites at room temperature in metals such as aluminum and iron under thermodynamic equilibrium. Artificially increasing vacancy concentrations by 1 to 7 orders of magnitude above equilibrium levels through quenching, irradiation, or deformation can significantly accelerate material strengthening. However, measuring vacancy concentrations below 10-7 in alloys and achieving spatial mapping remain challenging. Here, a vacancy-mediated gradient microstructure near grain boundaries is reported and analyzed to investigate diffusion enhancement and the local vacancy population in an Al-Zn system. This method uses cryogenic processes to preserve excess vacancies and halt microstructure evolution, enabling intermittent measurement of compositional fluctuations during ultrafast spinodal decomposition. It allows for the assessment of diffusion enhancement and determination of vacancy supersaturation in sub-micrometer regions. Liquid nitrogen-quenched Al-12.5 at.% Zn alloy shows a vacancy concentration of ≈10-7 at room temperature, dropping to 10-9 after 3 h, with significant spatial variation near grain boundaries. This work addresses gaps in understanding the evolution and distribution of vacancies across various measurement scales, advancing the control of vacancies to enhance the strengthening of engineering alloys.

Understanding the compositional evolution of core-shell L12 Al3(Sc,Zr) precipitates in aluminium alloys is critical for tailoring their mechanical performance. In this study, we combine atom probe tomography (APT) and anomalous small-angle X-ray scattering (ASAXS) to characterise, for the first time, the in situ chemical evolution of these precipitates during a two-step ageing treatment. APT confirms the sequential formation of a Sc-rich core followed by a Zr-enriched shell, while ASAXS, conducted near the Zr K-edge, enables time-resolved tracking of Zr incorporation during precipitation. Two alloys with and without Mg were compared to investigate the effects of Mg on the precipitation kinetics, morphology of precipitates and strengthening behaviour.

Nanometric precipitates in metallic alloys often have highly anisotropic shapes. Given the large grain size and non-random texture typical of these alloys, performing small- and wide-angle X-ray scattering (SAXS/WAXS) measurements on such samples for determining their characteristics (typically size and volume fraction) results in highly anisotropic and irreproducible data. Rotations of flat samples during SAXS/WAXS acquisitions are presented here as a solution to these anisotropy issues. Two aluminium alloys containing anisotropic precipitates are used as examples to validate the approach with a -45°/45° angular range. Clear improvements can be seen on the SAXS I(q) fitting and the consistency between the different SAXS/WAXS measurements. This method-ology results in more reliable measurements of the precipitate's characteristics, and thus allows for time- and space-resolved measurements with higher accuracy.

Early-stage clustering in two Al-Mg-Zn(-Cu) alloys has been investigated using atom probe tomography and transmission electron microscopy. Cluster identification by the isoposition method and a statistical approach based on the pair correlation function have both been applied to estimate the cluster size, composition, and volume fraction from atom probe data sets. To assess the accuracy of the quantification of clusters of different mean sizes, synthesized virtual data sets were used, accounting for a simulated degraded spatial resolution. The quality of the predictions made by the two complementary methods is discussed, considering the experimental and simulated data sets.

ODS steels are candidate materials for the future generation of nuclear power plants. Ferritic / Martensitic (F/M) ODS steels display better formability thanks to high temperature austenitic transformation. The precipitation kinetics of a F/M Fe-9Cr ODS steel during powder consolidation up to 1100 degrees C has been characterized by in-situ Small Angle X-ray Scattering (SAXS). The influence of the matrix phase transformation has been established, showing an increase of the growth rate of the nano-oxides in austenite, leading to nano-oxides similar to 2x larger in diameter than in Fe-14Cr ferritic ODS grades at the end of the thermal treatment. These results are further supported by local atom probe tomography (APT) performed across grains showing contrasted microstructure and composition. Anomalous SAXS as well as comparison between APT and SAXS provide evidence that the nano-oxides stabilize with a Y2Ti2O7 or Y2TiO5 stoichiometry around 1100 degrees C.

In this work, the transformation and dissolution/precipitation behaviour of the soft martensitic, precipitationhardening steel X5CrNiCuNb16-4 (often referred to as 17-4 PH or AISI 630) has been investigated by various analytical in situ techniques. First, austenite formation during the heating stage of a solution treatment (or austenitization) is examined. Subsequently, a major part of this work evaluates precipitation during cooling from the solution treatment (i.e., the quench-induced precipitation of Cu-rich particles). The following analytical in situ techniques were utilised: synchrotron high-energy X-ray diffraction, synchrotron small-angle X-ray scattering, differential scanning calorimetry, and dilatometry. These were complemented by ex situ high-angle annular dark-field scanning transmission electron microscopy coupled with energy-dispersive X-ray spectroscopy on as-quenched samples after various cooling rates. The continuous heating transformation and continuous cooling transformation diagrams have been updated. Contrary to previous reports, X5CrNiCuNb16-4 is rather quench sensitive and the final properties after ageing degrade if cooling is done slower than a certain critical cooling rate. Quench-induced Cu-rich precipitation happens in two reactions: a larger, nearly pure Cu facecentred cubic phase forms at higher temperatures, while at medium temperatures, spherical Cu-rich nanoparticles form, which are found to be body-centred cubic at room temperature. The dimensions of the quenchinduced particles range from several mu m after cooling at 0.0001 K s-1 down to just a few nm after cooling at 1 K s1. The maximum age hardening potential of X5CrNiCuNb16-4 can be exploited if a fully supersaturated solid solution is reached at cooling rates above the critical cooling rate of about 10 K s-1.

Microstructure design of new high-performance alloys requires the combination of multiple hardening mechanisms. This study explores combining nanograins with spinodal decomposition strengthening in an Fe-51.4Cr (at.%) alloy. High-pressure torsion (HPT) produced a nanostructure with a 51 nm grain size. Atom probe tomography analysis of deformed and annealed samples revealed spinodal decomposition after one hour of annealing. HPT accelerated decomposition kinetics is due to the high vacancy concentration. Microhardness remained stable due to spinodal hardening, despite a decrease in the Hall-Petch strengthening contribution. However, fracture toughness decreased.

The rates of atomic clustering and precipitation hardening are closely related to the diffusivity of solutes and the concentration of vacancies during the natural aging of aluminum alloys. The measurement of the diffusivity of solutes at room temperature, especially in systems with an equilibrium vacancy concentration, is beneficial to the design of the aging process. However, this measurement has long been challenging because of the extremely low diffusion rates of solutes in aluminum at room temperature and the presence of supersaturated vacancies. In this work, we propose a method to quantify the diffusivity of solutes based on the kinetic evaluation of the spinodal decomposition process. This evaluation involves conducting atom probe tomography experiments, analyzing the radial distribution function, and modeling the phase separation process using the Cahn-Hilliard theory. The aging experiments were conducted on nanoscale samples, where excess vacancies can be eliminated at free surfaces due to a high surface -to -volume ratio. The results yielded a diffusivity of Zn in the Al -12.5 at.% Zn alloy of (1.32 +/- 0.46) x 10-25 m2/s at 295 K. This work introduces a novel approach to assess the solute diffusivity under conditions of equilibrium vacancy concentration at room temperature and expands the temperature range for measuring the diffusivity in systems with spinodal decomposition, particularly in cases where kinetic data at low temperatures are scarce.

A round-robin study has been carried out to estimate the impact of the human element in small-angle scattering data analysis. Four corrected datasets were provided to participants ready for analysis. All datasets were measured on samples containing spherical scatterers, with two datasets in dilute dispersions and two from powders. Most of the 46 participants correctly identified the number of populations in the dilute dispersions, with half of the population mean entries within 1.5% and half of the population width entries within 40%. Due to the added complexity of the structure factor, far fewer people submitted answers on the powder datasets. For those that did, half of the entries for the means and widths were within 44 and 86%, respectively. This round-robin experiment highlights several causes for the discrepancies, for which solutions are proposed.

Achieving high yield strength via submicrometer grain size and nanoscaled precipitation has been reached in 7### aluminum alloys thanks to severe plastic deformation (SPD) by High Pressure Torsion (HPT) process. Unfortunately, this technique has inherently strong limitations since only small parts can be processed and the plastic strain is not homogeneous. These limitations prevent large scale production of Ultra Fine Grain (UFG) materials for potential applications. A recent severe plastic deformation process, High Pressure Sliding (HPS) developed by Fujioka and Horita, allows to homogeneously deform large scale sheets by shear at higher speed. In this work, the competition between precipitation, grain growth and recrystallization during heat treatments after SPD was studied in depth for an AlZnMgCu alloys deformed by HPS with two deformation levels (γ≈15 and γ≈20) in order to investigate if the high mechanical properties obtained by HPT can be reached by HPS. Microstructures analyses after deformation and ageing were carried out by transmission electron microscopy and in situ small angle X ray scattering and then related to the mechanical behavior evaluated by tensile tests. Experimental data show very similar microstructures after HPS and HPT, with a good thermal stability thanks to the competition between precipitation, recrystallization and recovery. The obtained microstructural features lead to exceptional yield strength (>800MPa) as compared to the classical aluminum alloys. This study is therefore very promising towards the aim of obtaining very high yield strength aluminum alloys suitable for applications.

A major drawback in ferritic steels production and usage is their mechanical brittleness at temperatures close to ambient temperature. Precipitation and grain size appear as two major parameters in such cleavage brittle behavior. This is why six model microstructures have been elaborated from the same base of chemical composition, but with different elements additions and thermal treatments. The base composition is 18% chromium and 2% molybdenum to ensure an entirely ferritic matrix at any temperature even with 0.015% of both carbon and nitrogen. The addition of titanium or niobium changed the nature, size and location of the carbides and nitrides, while carefully chosen heat treatments varied the size of the grains. Microstructure characterizations down to very fine scales (TEM, SANS) combined with thermodynamics and diffusion modeling allowed analyzing precipitates formation as well as remaining interstitial elements (carbon and nitrogen) in solution in the ferritic matrix. This multi-scale analysis of the microstructures is important to understand the mechanical behavior of the alloys, which will be presented in a companion paper.

To study the influence of ageing and drying steps onto the multiscale Mo active phase arrangement (i. e. MoS2 slabs and slab aggregates), a series of highly loaded CoMoP/gamma-Al2O3 catalysts aged, unaged, dried or freeze-dried were prepared and tested in toluene hydrogenation. Electron Probe Micro Analyses (EPMA) and Anomalous Small Angle X-Ray Scattering (ASAXS) permit to highlight the influence of each preparation steps. A growth of Mo entities occurs during ageing along with metal diffusion inside the support and leads to longer slabs. The same occurs during drying with metal redistribution due to solvent evaporation. Concomitantly, a fragmentation of slab aggregates takes place and leads to numerous small slabs aggregates. Slab length and aggregates amount were found to drive the catalytic activity, which translates the relationship between activity, number of active sites and their accessibility. Conversely, macroscopic metal distribution into the extrudates appears to have no impact on the catalytic performance.

Laser additive manufacturing (LAM) offers high flexibility in the production of customized and geometrically complex parts. The technique receives great interest from industry and academia but faces substantial challenges regarding processability and insufficient mechanical properties of LAM-produced material. One reason is that currently mainly conventional alloys are being used in LAM, which were developed for different processes such as casting. Since these alloys are not optimized for the specific process conditions encountered in LAM such as fast cooling and cyclic re-heating, they cannot be expected to perform ideally in such processes regarding processability and resulting mechanical properties. Here we present the development of a new, simple ternary Fe-NiTi maraging-type alloy tailor-made for LAM. We used compositionally graded samples to screen Ti compositions from 0 to 21 at. % and efficiently identify promising microstructures and mechanical properties. Under LAM solidification conditions the desired mainly martensitic microstructure needed for a maraging steel formed at Ti compositions ranging from 0 to 7 at. %. Within this composition range, the intended microstructure is formed and additionally some unique process conditions of LAM such as cyclic re-heating can be exploited. Specifically, in-situ phase transformations can be controlled during LAM, via the thermal history. At higher Ti compositions two different eutectic microstructures with different primary phases were found that show a high hardness of up to 700 HV.

Aluminum alloys designed for laser powder bed fusion (L-PBF) often show a bimodal grain structure and a strong out-of-equilibrium character with heterogeneities developing at scales ranging from the melt pool, i.e. several hundred microns, down to sub-nanometer. When subjected to post-fabrication heat treatments, microstructural evolutions arise at all scales. Herein are established the relationships between microstructure and mechanical properties at room temperature of a novel Al-4Mn-3Ni-2Cu-1Zr alloy, designed for L-PBF and subjected to direct ageing. On the basis of a multiscale microstructural study using scanning-electron microscopy (SEM), automated orientation mapping in the transmission-electron microscope (TEM-ACOM), atom probe tomography (APT), and synchrotron small-angle X-ray scattering (SAXS), we discuss and weigh the role of multiple strengthening mechanisms to the high strength of the material. In the stress-relieved conditions (300 degrees C/4 h), the yield strength is about 320 MPa and solid solution strengthening accounts for nearly two third of the yield strength (similar to 200 MPa) thanks to a very high content of Mn retained in solid solution (> 1.5 at.%) and, to a lesser extent, grain boundary strengthening. After ageing at 400 degrees C/1 h, the yield strength reaches 410 MPa. The additional contribution is brought by precipitation strengthening by L1(2)-ordered Al3Zr, and to a lesser extent, Mn-rich precipitates. The composite effect due to the large fraction of relatively fine (< 1 mu m) intermetallic particles (similar to 20%) is highlighted and cannot be neglected. This work provides guidelines to further optimize the mechanical properties and thermal stability of Al-alloys designed for L-PBF.