Synchrotron X-rays and neutrons for structural characterization of steels and cemented carbides
Background
Due to their penetration power and reciprocal space coverage, high-energy X-rays are well suited for in-situ investigations of bulk polycrystalline materials. Neutrons are also suitable for the same purpose but they provide higher penetration power and lower temporal resolution. The neutron scattering cross-sections (contrast) are also different from X-rays and e.g. in the case of phase separation in Fe-Cr, neutron scattering is more powerful. Advanced metallic materials are characterized by complex microstructures. Typical features are the occurrence of multiple types of phases and interfaces, chemically and structurally graded zones, grain boundaries and complex dislocation patterns to name a few. These structures are formed by phase transformations or closely related processes. Some of the transformations are displacive and the associated motion of the underlying lattice defects is often believed to occur at very high rates close to the speed of sound. Examples are formation of plate martensite in Fe-base alloys and nano-twins in Fe-Mn. Other processes involving atomic diffusion are usually much slower, e.g. nano-precipitates in Fe-Si-Cu, interface equilibrium segregations and forced solid solutions that entail nano-transformations in Fe-C or spinodal decomposition occurring in Fe-Cr. Though the diffusional processes are much slower than the diffusionless phenomena, the diffusion distances are very short in nanoscale phase transformations and thus to resolve the detailed mechanisms, high time resolution is often necessary. The equilibrium and defect structures associated with nanoscale phase transformations are characterized by their chemical composition, lattice and interface structures, and dispersion (size, volume fraction). Traditionally these structures have been observed in samples that have been processed under various conditions and then cooled to room temperature and made into specimens and finally put into different kinds of microscopes. In situ observation of the bulk of the material at high temperatures of how these nanoscale features evolve during processing is not possible without the use of brilliant synchrotron radiation or possibly neutrons. Another important aspect on the utilization of synchrotron X-rays and neutrons for characterization of materials is high-throughput characterization, an important topic within ICME. By using these techniques it is possible to speed up the characterization of materials several orders of magnitude, compared to lab-scale XRD or electron microscopes. Both in-situ and high-throughput characterization will be explored within this project.
Scientific goals
- Establish high-throughput experimental analysis of materials structures at Hero-m 2i.
- Establish in-situ analysis of materials structures at Hero-m 2i.
- Investigate phase separation of Fe-Cr alloys and carbides in-situ.
- Investigate deformation characteristics of steels and cemented carbides.
- Enable in-situ studies of carbide grain growth during sintering of cemented carbides.
Industrial goals
- Build know-how of high-throughput experimental analysis of materials structures.
- Build know-how of in-situ analysis of materials structures.
- Build know-how of quantitative bulk analysis of materials structures.
Project plan
The experimental methodologies that will be used are briefly outlined here. Powder XRD and 3DXRD will be used to investigate deformation and phase transformations in steels and cemented carbides. Small-angle scattering (SAS) and possibly total scattering will be used to study phase separation in Fe-Cr and carbides. Different methodologies for the investigation of carbide grain growth during sintering of cemented carbides will be explored. The work is divided in 4 work packages:
WP-1: Characterization of deformation
WP-2: Characterization of phase separation
WP-3: Characterization of austenite decomposition
WP-4: Characterization of carbide grain growth
Partners of the project are all Hero-m 2i partners.
Funding agency
Vinnova through the Hero-m 2i center.
Beginning and end dates
2017-05-01 to 2022-05-01.
Project contacts
More information
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