High-speed tomography under extreme conditions at the PSICHE beamline of the SOLEIL Synchrotron

Understanding the hot isostatic pressing effectiveness of laser powder bed fusion Ti-6Al-4V by in-situ X-ray imaging and diffraction experiments

In the present study, in-situ observation of Hot Isostatic Pressure (HIP) procedure of laser powder bed fusion manufactured Ti-6Al-4V parts was performed to quantitatively estimate the densification rate of the material and the influence of the defect initial size and shape on such rate. The observations were performed in-situ using the Ultrafast Tomography Paris-Edinburgh Cell and the combination of fast phase-contrast synchrotron X-ray tomography and energy dispersive diffraction. With this strategy, we could quantify how the effectiveness of HIP depends on the characteristics of a defect. Smaller defects showed a higher densification rate, while the defect shape did not have significant effect on such rate.

Deformation of two-phase aggregates with in situ X-ray tomography in rotating Paris-Edinburgh cell at GPa pressures and high temperature

High-pressure (>1 GPa) torsion apparatus can be coupled with in situ X-ray tomography (XRT) to study microstructures in materials associated with large shear strains. Here, deformation experiments were carried out on multi-phase aggregates at ∼3-5 GPa and ∼300-500°C, using a rotational tomography Paris-Edinburgh press (RoToPEc) with in situ absorption contrast XRT on the PSICHE beamline at Synchrotron SOLEIL. The actual shear strain reached in the samples was quantified with respect to the anvil twisting angles, which is γ ≤ 1 at 90° anvil twist and reaches γ ≃ 5 at 225° anvil twist. 2D and 3D quantifications based on XRT that can be used to study in situ the deformation microfabrics of two-phase aggregates at high shear strain are explored. The current limitations for investigation in real time of deformation microstructures using coupled synchrotron XRT with the RoToPEc are outlined.

Recent Developments of High-Pressure Spark Plasma Sintering: An Overview of Current Applications, Challenges and Future Directions

Spark plasma sintering (SPS), also called pulsed electric current sintering (PECS) or field-assisted sintering technique (FAST) is a technique for sintering powder under moderate uniaxial pressure (max. 0.15 GPa) and high temperature (up to 2500 °C). It has been widely used over the last few years as it can achieve full densification of ceramic or metal powders with lower sintering temperature and shorter processing time compared to conventional processes, opening up new possibilities for nanomaterials densification. More recently, new frontiers of opportunities are emerging by coupling SPS with high pressure (up to ~10 GPa). A vast exciting field of academic research is now using high-pressure SPS (HP-SPS) in order to play with various parameters of sintering, like grain growth, structural stability and chemical reactivity, allowing the full densification of metastable or hard-to-sinter materials. This review summarizes the various benefits of HP-SPS for the sintering of many classes of advanced functional materials. It presents the latest research findings on various HP-SPS technologies with particular emphasis on their associated metrologies and their main outstanding results obtained. Finally, in the last section, this review lists some perspectives regarding the current challenges and future directions in which the HP-SPS field may have great breakthroughs in the coming years.

In situ characterization of liquids at high pressure combining X-ray tomography, X-ray diffraction and X-ray absorption using the white beam station at PSICHÉ

A novel experimental setup dedicated to the study of liquid and amorphous materials, on the white beam station of the PSICHÉ beamline at SOLEIL, is described. The Beer-Lambert absorption method has been developed using a broad-spectrum (white) incident beam for in situ density measurements at extreme conditions of pressure and temperature. This technique has been combined with other existing X-ray techniques (radiographic imaging, tomography and combined angle energy dispersive X-ray diffraction). Such a multi-technical approach offers new possibilities for the characterization of liquid and amorphous materials at high pressure and high temperature. The strength of this approach is illustrated by density measurements of liquid gallium at pressures up to 4 GPa, combining the three independent X-ray techniques (the Beer-Lambert absorption method, tomography and X-ray diffraction).

Quantitative 4D X-ray microtomography under extreme conditions: a case study on magma migration

X-ray computed tomography (XCT) is a well known method for three-dimensional characterization of materials that is established as a powerful tool in high-pressure/high-temperature research. The optimization of synchrotron beamlines and the development of fast high-efficiency detectors now allow the addition of a temporal dimension to tomography studies under extreme conditions. Presented here is the experimental setup developed on the PSICHE beamline at SOLEIL to perform high-speed XCT in the Ultra-fast Tomography Paris-Edinburgh cell (UToPEc). The UToPEc is a compact panoramic (165° angular aperture) press optimized for fast tomography that can access 10 GPa and 1700°C. It is installed on a high-speed rotation stage (up to 360° s^-1) and allows the acquisition of a full computed tomography (CT) image with micrometre spatial resolution within a second. This marks a major technical breakthrough for time-lapse XCT and the real-time visualization of evolving dynamic systems. In this paper, a practical step-by-step guide to the use of the technique is provided, from the collection of CT images and their reconstruction to performing quantitative analysis, while accounting for the constraints imposed by high-pressure and high-temperature experimentation. The tomographic series allows the tracking of key topological parameters such as phase fractions from 3D volumetric data, and also the evolution of morphological properties (e.g. volume, flatness, dip) of each selected entity. The potential of this 4D tomography is illustrated by percolation experiments of carbonate melts within solid silicates, relevant for magma transfers in the Earth's mantle.