In this study, we investigate the precipitation kinetics of Cu in 15–5 PH maraging stainless steel during high-temperature thermal treatments in the fully austenitic state. This provides direct evidence that Cu precipitation can occur in the austenite phase of martensitic or ferritic steels. The kinetics of Cu precipitation in austenite are examined at 700 and 800 °C using in situ synchrotron small-angle and wide-angle X-ray scattering, complemented by atom probe tomography investigations to analyze the precipitates, particularly their chemistry, following heat treatment. The resulting experimental data, which include the evolution of size, volume fraction, number density and chemical composition, are used to inform precipitation kinetics modelling using the Langer-Schwartz-Kampmann-Wagner (LSKW) approach coupled with CALPHAD thermodynamic and kinetic databases. The simulations accurately capture the experimental data by adjusting the interfacial energy in an inverse modelling approach. The insight that Cu precipitation occurs in austenite and subsequently in martensite paves the way for design of hierarchical structures with a bi-modal particle size distribution of Cu precipitates with varying crystal structures and compositions. Additionally, the validated LSKW modelling approach establishes a foundation for designing Cu-alloyed high-performance steels, taking into account various manufacturing routes.

Impact toughness is essential for evaluating the mechanical properties of ship hull steels. This study focused on understanding the embrittlement mechanism of NiAl precipitation-strengthened HSLA steels by integrating advanced characterization and atomic-scale calculations. The factors causing the deterioration of the impact toughness of NiAl precipitation-strengthened steels, which have been contentious, were identified. The embrittlement mechanism and crack propagation mode were revealed using first-principles calculations and 3D impact fracture morphology, respectively. The results suggested that the numerous homogeneous NiAl nanoparticles within the bcc-Fe matrix reduced the impact toughness of the HSLA steels. As the precipitate interparticle spacing (L) decreased, the impact toughness decreased until it attained a critical value (similar to 27 nm). This is interpreted effectively by the calculations indicating that the shear modulus (75 GPa) and fracture energy (4.5 J/m(2)) of the NiAl phase, particularly the NiAlMn phase (46 GPa, 4 J/m(2)), are significantly lower than those of bccFe (83 GPa, 5 J/m(2)). This induces the fracture of nanoparticles under rapid impact loading, which functions as numerous crack initiations before plastic deformation of the matrix. The small L achieved after peak-hardening aging can result in the interconnection of these crack sources and cause instantaneous cleavage fractures, similar to brittle materials.

To enhance the fundamental understanding for micromechanical lath martensite deformation, the microstructure as well as macro- and microscopic tensile properties of as -quenched 15-5 PH stainless steel are systematically analysed depending on the austenitisation temperature. Based on electron backscatter diffraction (EBSD) and backscattered electron (BSE) analysis, it is noted that the martensite morphology alters from a less defined to a more clearly defined parallel arrangement of the block and lath structure with increasing temperature. For an indepth quantification of the hierarchical boundary strengthening contributions in relation to local stress/strain heterogeneity, separate high-fidelity virtual microstructures are realised for the different scales (prior austenite grains, packets and blocks). This is consistent with the materials transformation process. The virtual microstructures are simulated employing the crystal plasticity finite element method (CPFEM) adapted for handling high dislocation density and encompassing all relevant strengthening mechanisms by boundaries, dislocations and solute atoms. While accurately capturing the measured size -dependent stress-strain behaviour, the simulations reveal in line with the experiments (Hall-Petch) that blocks are the most effective dislocation motion barrier, causing increased strain hardening and stress/strain heterogeneity. Furthermore, since strain localisation is predicted strongest in the distinct block structure, the experimentally observed early plastic material yielding is thought to be favoured here.

Targeting to obtain fine dispersions of nanoscale precipitates to enhance the mechanical properties of a highperformance tool steel, re-engineering of the alloy composition and heat treatment was guided by computational thermodynamics and kinetics. A prototype alloy was prepared using the designed chemistry and heat treatment. Thereafter, advanced microstructural characterization and mechanical testing confirmed the successful design to reach a high number density of (V, Mo)C precipitates with an average diameter of about 5 nm in the peak-hardened condition, after tempering the martensite at 600 degrees C for 2 h.

This technical report presents an overview of sample environments which are usable at the PETRA III Swedish Materials Science beamline (potentially requiring arrangement or development of the beamline layout). Alongside the description of each sample environment, illustrative materials science studies are presented that exemplify the use of these sample environments for in situ and/or in operando measurements.  The sample environments are catalogued according to the research application areas, which are categorised as Thermal treatments, Electrochemistry, Catalysis, Thin films, Mechanical response of materials and Levitation. Such cataloguing means that researchers can now start their search for relevant sample environments by looking up a relevant research application area. Citations and links to specifications, published research cases and the organisation that is responsible for a given sample environment, are also provided as a basis for researchers to proceed with their research planning.

An analytical flow stress model, based on isotropic strain gradient plasticity theory, for precipitation hardened materials, is proposed and evaluated against tensile data on a 15 wt% Cr - 5 wt% Ni (15-5) PH stainless steel. The 15-5 PH material was aged at 500 °C for 1 h, 2 h, 5 h and 50 h to obtain a wide range of precipitate sizes. Detailed characterisation of precipitates was obtained using atom probe tomography (APT). A second material, a 15-5 stainless steel without added Cu was heat treated to obtain a similar matrix microstructure as in the 15-5 PH, but without Cu precipitates. Tensile testing revealed that the heat treated 15-5 PH material covered the full range from under- to overaged conditions. The analytical model, which accounts for stress reducing effects of plastic relaxation around particles, manages to capture the experimental data in a very satisfying manner using only a total of three tunable parameters. It is believed that the proposed model can offer an alternative to the much more commonly used work hardening models based on the internal variable approach.

This inventory catalogs the software programs that have proven to be useful to the Swedish research community that conducts research at the PETRA III synchrotron, including the PETRA III Swedish Materials Science beamline.

Based on publications from 2018, the inventory categorizes the various software programs used in research as either data reduction software for 2D area detector X-ray scattering images or data analysis software for WAXS, SAXS, GIWAXS, GISAXS, and PDF.

Each software program has a short description of its functionality, a note of its developer, links to the original publication describing the scientific method that the software is based upon, as well as the site for downloading the software program. 

The solidification and microstructural evolution during deposition, as well as the structural evolution during post heat treatment, determine the mechanical properties of wire-arc additively manufactured maraging stainless steels. In the present work, we tune the austenite reversion and nanoscale precipitation during post heat treat-ment and achieve an excellent combination of strength and ductility (ultimate tensile strength-1340 MPa and uniform elongation-10.5 %). The structural evolution is studied through computational thermodynamics, electron microscopy, in situ small-angle neutron scattering, and synchrotron X-ray diffraction. The as-built microstructure is composed of mainly martensite and retained austenite (-30 vol%) together with a minor fraction of delta-ferrite, M23C6, Nb(C, N), spherical and ellipsoidal Cu precipitates and some inclusions. The presence of these phases cannot be fully predicted by the Scheil-Gulliver model due to the complicated thermal history and non-homogenous elemental distribution. The reverted austenite formed during the post heat treatments has high stability and fine grain size (-1 mu m), which contributes to the excellent ductility, while the nanoscale precipi-tation hardening contributes to the achieved high strength.

Precipitation hardening is one of the most important strengthening mechanisms in metallic materials, and thus, controlling precipitation is often critical in optimizing mechanical performance. Also other performance requirements such as functional and degradation properties are critically depending on precipitation. Control of precipitation in metallic materials is, thus, vital, and the approach presently in the limelight for this purpose is an integrated approach of theory, computations and experimental characterization. An empirical understanding is essential to build physical models upon and, furthermore, quantitative experimental data is needed to build databases and to calibrate the models. The most versatile tool for precipitation characterization is the transmission electron microscope (TEM). The TEM has sufficient resolving power to image even the finest precipitates, and with TEM-based microanalysis, overall quantitative data such as particle size distribution, volume fraction and number density of particles can be gathered. Moreover, details of precipitate structure, morphology and chemistry, can be revealed. TEM-based postmortem and in situ analysis of precipitation has made significant progress over the last decade, largely stimulated by the widespread application of aberration corrected microscopes and accompanying novel analytics. The purpose of this report is to review these recent developments in precipitation analysis methodology, including sample preparation. Application examples are provided for precipitation analysis in metals, and future prospects are discussed.