Recent advances in Bragg coherent diffraction imaging (BCDI) experimental techniques permit routine measurement of multiple Bragg peaks from a single crystalline grain. The resulting images contain the full lattice distortion vector field which can be differentiated to provide lattice strain and rotation. With the advent of fourth-generation synchrotron light sources, such multi-peak datasets are produced at high rates, facilitating the need for rapid phase retrieval of the multiple peaks and subsequent image analysis. Here we describe and demonstrate a new implementation of a coupled phase retrieval technique for multi-peak BCDI which simultaneously treats each Bragg peak of the dataset and produces a three-dimensional image of the crystal s morphology and lattice distortion field. In addition, this method uses the redundant information contained in the various Bragg diffraction patterns to detect and suppress spurious signal appearing on the detector in a subset of the measurements. Compared with manual data editing, adaptive coupling produces a more consistent phase profile in reciprocal space and sharper surfaces in direct space, with no significant difference in computational cost. These improvements reduce the need for manual preprocessing and enable robust high-throughput analysis of multi-peak BCDI data, supporting near-real-time strain microscopy at modern synchrotron facilities.

Three samples of an AZ31 alloy with distinct textures were produced through chill casting, hot extrusion and hot rolling. The as-cast material exhibited a relatively random texture, while the hot extruded and hot rolled materials displayed \$\$$\backslash$left$\backslash$\ \hki0\ $\backslash$right$\backslash$\\$\$prism and \$\$$\backslash$left( \0001\ $\backslash$right)\$\$basal textures, respectively. This also led to significant differences in the characteristics of their grain boundary networks (i.e., the distribution of misorientations and plane orientations). The misorientation angle distribution of as-cast condition was similar to a random distribution. However, the other processing routes were significantly different from random, displaying a pronounced peak at \~ 30 deg misorientation angle, beyond which the distribution differed depending on the processing condition. Synthetically generated orientations belonging to each texture had misorientation angle distributions comparable to those measured for each processing route. This confirmed that the texture characteristics dictate the population of boundary misorientations. The distribution of grain boundary planes was anisotropic for all conditions, though the extent of anisotropy and their distribution characteristics depended on the processing route. It appeared that the relative areas of the grain boundary planes are largely influenced by the characteristics of the overall texture, where the hot rolling process promoted the \$\$$\backslash$left( \0001\ $\backslash$right)\$\$basal plane orientation, while the \$\$$\backslash$left$\backslash$\ \hki0\ $\backslash$right$\backslash$\\$\$prismatic plane orientation, which does not necessarily have low energy, was dominant for the hot extrusion condition.

Changes in the texture and CSL boundary distribution during cold rolling and annealing of a commercial grade Interstitial Free (IF) steel have been investigated. The CSL boundaries associated with different texture components were isolated, using TSL Texture Analysis software. This was done for both individual components of texture, as well as for groups of components belonging to the γ (ND//〈111〉) and the α (RD//〈110〉) fibers. The total lengths as well as number fractions of various CSL boundaries related to different texture types were then determined. The results clearly show that each texture (individual component or a group of components) is associated with a particular CSL grain boundary distribution (CGBD). The plots of CSL number fraction and total length against the CSL boundary appear to be rather similar in shape. The density of Σ3 boundaries is the highest among all the CSL boundaries for all the textural conditions. In general, the total CSL fraction shows an increase from the cold worked to the recrystallization stage; although there is a decrease in the total CSL fraction after grain growth. Generally, the number fraction of CSL boundaries is higher in case of the RD texture grains as compared to the ND oriented grains. During grain growth, however, there is an increase in the ND related CSL boundaries, while the RD related CSL fraction shows a decrease. Heavy cold rolling and annealing leads to refinement of grain size and improve mechanical properties. An attempt has been made to explain the above observations with the help of texture and microstructure data.

High-performance heat exchangers are essential components in applications related to aerospace, industrial processes, and power generation. In power generation, the primary heat exchangers (HX) in future supercritical fluid Brayton cycles need to operate at temperatures in excess of 700 $\,^\circ$C and pressures of 200 bar, necessitating the need for novel designs, high-temperature alloys, and new manufacturing methods to develop compact and high efficiency components. In this work, the design, fabrication, and experimental characterization of an additively manufactured (AM) primary HX for chloride molten salt (MS) to supercritical carbon dioxide (sCO2) is presented. The primary HX can also be used for extracting heat from a high temperature waste heat stream to sCO2. The primary HX is fabricated with Haynes 282 alloy via laser powder bed fusion AM. The core of the primary HX is comprised of a pin array on the sCO2 side and a three-dimensional periodic lattice network on the hot side. The sCO2 headers are aerodynamic in shape and are integrated within the MS flow path to permit scalability of the primary HX and permit a near counter-flow exchange of heat. A 20-pair primary HX is experimentally characterized using 200 bar sCO2 on the cold side and heated air as a surrogate for chloride MS on the hot side. Experimental results are used to validate a core thermofluidic model for the primary HX. The model predicts heat transfer rate and exit temperature of the air and sCO2 streams, on average, to within 1.72 %, 0.75 %, and 1.46 %, respectively. The validated model is used to estimate the volumetric and gravimetric power density of the MS-sCO2 heat exchanger, and the impact of varying inlet temperatures and flow rates of both streams on the primary HX performance. Considerations for AM fabrication and assembly of a modular 1 MW unit are provided.

Laser processing has been widely employed in various applications due to its exceptional spatial resolution. However, the rapid temperature gradients generated in localized areas present significant challenges for experimental characterization using conventional instruments. To characterize Ni alloy 718 during laser processing, we employed in-situ synchrotron X-ray diffraction with a high-speed detector, a method particularly well-suited for probing processes with high temporal and spatial resolution. Through a series of in-situ experiments, we investigated the local variations in the evolution of microstructures and thermomechanical behaviors within a keyhole mode melt pool. The in situ macroscopic thermomechanical behaviors were quantified using an empirical model derived from diffraction patterns, with experimental results showing reasonable agreement with finite element analysis. Various laser parameters were tested to assess their influences on the residual strains in the melt pools. The results revealed that the residual strain in the keyhole mode melt pool is relatively insensitive to variations in the parameters and is smaller than that in the melt pool created under conduction mode laser scanning. Additionally, we analyzed the shapes of individual diffraction spots, providing insights into the plastic behaviors and compositional developments in the resolidified alloy. The analysis confirmed that compositional variations in a dendritic microstructure manifest as asymmetric broadening of the diffraction spots.