Synchrotron‐Based Micro‐CT and Refraction‐Enhanced Micro‐CT for Non‐Destructive Materials Characterisation

Abstract

X‐ray computed tomography is an important tool for non‐destructively evaluating the 3‐D microstructure of modern materials. To resolve material structures in the micrometer range and below, high brilliance synchrotron radiation has to be used. The Federal Institute for Materials Research and Testing (BAM) has built up an imaging setup for micro‐tomography and ‐radiography (BAMline) at the Berliner storage ring for synchrotron radiation (BESSY). In computed tomography, the contrast at interfaces within heterogeneous materials can be strongly amplified by effects related to X‐ray refraction. Such effects are especially useful for materials of low absorption or mixed phases showing similar X‐ray absorption properties that produce low contrast. The technique is based on ultra‐small‐angle scattering by microstructural elements causing phase‐related effects, such as refraction and total reflection. The extraordinary contrast of inner surfaces is far beyond absorption effects. Crack orientation and fibre/matrix debonding in plastics, polymers, ceramics and metal‐matrix‐composites after cyclic loading and hydro‐thermal aging can be visualized. In most cases, the investigated inner surface and interface structures correlate to mechanical properties. The technique is an alternative to other attempts on raising the spatial resolution of CT machines.

Evolution of porosity, crack density, and CMAS penetration in thermal barrier coatings subjected to burner rig testing

“…Synchrotron X-ray refraction radiography (SXRR) measurements were carried out at the BAM synchrotron laboratory BAMline at Helmholtz-Zentrum Berlin, Germany. 20,21 Three of the specimens that were subjected to CMAS deposition (20,35, and 70 cycles) as well as the reference specimen (G) were mounted in a slide frame as shown in Figure 4.…”

Evolution of Thermal Microcracking in Refractory ZrO2-SiO2 after Application of External Loads at High Temperatures

“…with size (~1 nm) well below their spatial resolution (~1 μm in the best case) as well as that of computed tomography. This detection power has been exploited in previous works using X-ray refraction [15,16], whereas model has been elaborated to rationalize the evolution of a network of microcracks in terms of propagation of large microcracks that could lead to the closure of smaller ones.…”

X-ray refraction distinguishes unprocessed powder from empty pores in selective laser melting Ti-6Al-4V

“…The keyhole pores show diameters of up to 50 μm. The synchrotron X-ray refraction radiography (SXRR) experiments were carried out at the BAMline [13,14] (Figure 3), located at the synchrotron light source BESSY II (Helmholtz-Zentrum Berlin), utilizing the X-refraction technique called analyzer based imaging (ABI). The samples were thin plates with a thickness of 0.35 mm cut perpendicular to the building direction from the middle of the cuboids and polished on both sides using a SiC grinding paper up to 4000 grit.…”