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.

Surface growth, i.e., the addition or removal of mass from the boundary of a solid body, occurs in a wide range of processes, including the growth of biological tissues, solidification and melting, and additive manufacturing. To understand nonlinear phenomena such as failure and morphological instabilities in these systems, accurate numerical models are required to study the interaction between mass addition and stress in complex geometrical and physical settings. Despite recent progress in the formulation of models of surface growth of deformable solids, current numerical approaches require several simplifying assumptions. This work formulates a method that couples an Eulerian surface growth description to a phase-field approach. It further develops a finite element implementation to solve the model numerically using a fixed computational domain with a fixed discretization. This approach bypasses the challenges that arise in a Lagrangian approach, such as having to construct a four-dimensional reference configuration, remeshing, and/or changing the computational domain over the course of the numerical solution. It also enables the modeling of several settings — such as non-normal growth of biological tissues and stress-induced growth — which can be challenging for available methods. The numerical approach is demonstrated on a model problem that shows non-normal growth, wherein growth occurs by the motion of the surface in a direction that is not parallel to the normal of the surface, that can occur in hard biological tissues such as nails, horns, etc. Next, a thermomechanical model is formulated and used to investigate the kinetics of freezing and melting in ice under complex stress states, particularly to capture regelation which is a key process in frost heave and basal slip in glaciers.

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.

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.

To investigate the difference between ionic and electronic conductors as infiltrates in solid oxide fuel cells (SOFCs), high -throughput and high-performance finite element simulations were carried out on 51 different cathode microstructures. Five cathode backbones, reconstructed from a commercial SOFC, were infiltrated computationally with varying number densities of nanoscale electronically or ionically conducting particles. Local electrochemical quantities were computed within the volumetric meshes that represent the complex 3D microstructural morphologies that include the infiltrated particles. As infiltrates, ionic conductors improve the performance more than electronic conductors. By differentiating transport and reaction pathways originating from backbone phases and infiltrates, we show that new ionic transport pathways opened by the ionically conducting infiltrates are the origin of this difference. These new transport paths redistribute current throughout the cathode, thereby increasing (decreasing) the available local activation (Ohmic) overpotential at triple phase boundaries and rendering them more active than for the case of electronic conductors as infiltrates. These results give us insight to engineering improved electrodes for SOFCs via infiltration with surface active nano -particles.