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Since the 4th 1998 edition, there have been numerous crucial advances to the modelling and the basic understanding of solidification phenomena, and with its linking to experimental results.

Solidification with LaZnAl11O19 ceramics is one of the feasible strategies for treating high-alumina high-level waste. With the utilization of 12.5 wt% boric acids as flux, high-purity LaZnAl11O19 was obtained by solid-state method at 1450°C for 12 h. It was demonstrated that adding H3BO3 flux not only increased the purity of the samples and lowered the synthesis temperature, but also improved their micromorphology.

Solute transport during rapid and repeated thermal cycle in additive manufacturing (AM) leading to non-equilibrium, non-uniform microstructure remains to be studied. Here, a fully-coupled fluid dynamics and microstructure modelling is developed to rationalise the dynamic solute transport process and elemental segregation in AM, and to gain better understanding of non-equilibrium nature of intercellular solute segregation and cellular structures at sub-grain scale during the melting-solidification of the laser powder bed fusion process. It reveals the solute transport induced by melt convection dilutes the partitioned solute at the solidification front and promotes solute trapping, and elucidates the mechanisms of the subsequent microstructural morphology transitions to ultra-fine cells and then to coarse cells. These suggest solute trapping effect could be made used for reducing crack susceptibility by accelerating the solidification process. The rapid solidification characteristics exhibit promising potential of additive manufacturing for hard-to-print superalloys and aid in alloy design for better printability. Solute transport during rapid and repeated thermal cycles is important in additive manufacturing process. Here, the authors develop a fully-coupled model to rationalise solute transport process, elemental segregation, and non-equilibrium solid/liquid interfacial evolution at sub-grain scale.

Phase-field modeling of dendritic growth presents the state of the art in the field of solidification modeling and are usually implemented using finite difference models combined with explicit time marching and accelerated by using GPUs. They are a prime candidate for such acceleration, since they require many arithmetic operations on relatively low ammount of data. We present an attempt at porting an existing RBF-FD code optimized for CPU execution to use GPU acceleration while keeping the resulting implementation portable between architectures. We discuss the acceleration achieved, scaling and implementation issues and critically discuss current landscape of GPGPU offerings.

Additive manufacturing, often known as three-dimensional (3D) printing, is a process in which a part is built layer-by-layer and is a promising approach for creating components close to their final (net) shape. This process is challenging the dominance of conventional manufacturing processes for products with high complexity and low material waste 1 . Titanium alloys made by additive manufacturing have been used in applications in various industries. However, the intrinsic high cooling rates and high thermal gradient of the fusion-based metal additive manufacturing process often leads to a very fine microstructure and a tendency towards almost exclusively columnar grains, particularly in titanium-based alloys 1 . (Columnar grains in additively manufactured titanium components can result in anisotropic mechanical properties and are therefore undesirable 2 .) Attempts to optimize the processing parameters of additive manufacturing have shown that it is difficult to alter the conditions to promote equiaxed growth of titanium grains 3 . In contrast with other common engineering alloys such as aluminium, there is no commercial grain refiner for titanium that is able to effectively refine the microstructure. To address this challenge, here we report on the development of titanium–copper alloys that have a high constitutional supercooling capacity as a result of partitioning of the alloying element during solidification, which can override the negative effect of a high thermal gradient in the laser-melted region during additive manufacturing. Without any special process control or additional treatment, our as-printed titanium–copper alloy specimens have a fully equiaxed fine-grained microstructure. They also display promising mechanical properties, such as high yield strength and uniform elongation, compared to conventional alloys under similar processing conditions, owing to the formation of an ultrafine eutectoid microstructure that appears as a result of exploiting the high cooling rates and multiple thermal cycles of the manufacturing process. We anticipate that this approach will be applicable to other eutectoid-forming alloy systems, and that it will have applications in the aerospace and biomedical industries. Titanium–copper alloys with fully equiaxed grains and a fine microstructure are realized via an additive manufacturing process that exploits high cooling rates and multiple thermal cycles.

This article overviews the scientific results of the microstructural features observed in 316 L stainless steel manufactured by the laser powder bed fusion (LPBF) method obtained by the authors, and discusses the results with respect to the recently published literature. Microscopic features of the LPBF microstructure, i.e., epitaxial nucleation, cellular structure, microsegregation, porosity, competitive colony growth, and solidification texture, were experimentally studied by scanning and transmission electron microscopy, diffraction methods, and atom probe tomography. The influence of laser power and laser scanning speed on the microstructure was discussed in the perspective of governing the microstructure by controlling the process parameters. It was shown that the three-dimensional (3D) zig-zag solidification texture observed in the LPBF 316 L was related to the laser scanning strategy. The thermal stability of the microstructure was investigated under isothermal annealing conditions. It was shown that the cells formed at solidification started to disappear at about 800 °C, and that this process leads to a substantial decrease in hardness. Colony boundaries, nevertheless, were quite stable, and no significant grain growth was observed after heat treatment at 1050 °C. The observed experimental results are discussed with respect to the fundamental knowledge of the solidification processes, and compared with the existing literature data.

W NbMoTa refractory high-entropy alloys with four different tungsten concentrations ( = 0, 0.16, 0.33, 0.53) were fabricated by laser cladding deposition. The crystal structures of W NbMoTa alloys are all a single-phase solid solution of the body-centered cubic (BCC) structure. The size of the grains and dendrites are 20 μm and 4 μm on average, due to the rapid solidification characteristics of the laser cladding deposition. These are much smaller sizes than refractory high-entropy alloys fabricated by vacuum arc melting. In terms of integrated mechanical properties, the increase of the tungsten concentration of W NbMoTa has led to four results of the Vickers microhardness, i.e., = 459.2 ± 9.7, 476.0 ± 12.9, 485.3 ± 8.7, and 497.6 ± 5.6. As a result, NbMoTa alloy shows a yield strength (σ ) and compressive strain (ε ) of 530 Mpa and 8.5% at 1000 °C, leading to better results than traditional refractory alloys such as T-111, C103, and Nb-1Zr, which are commonly used in the aerospace industry.

Cryogenic carbon capture (CCC) can preferentially desublimate$\\text {CO}_2$out of the flue gas. A widespread application of CCC requires a comprehensive understanding of$\\text {CO}_2$desublimation properties. This is, however, highly challenging due to the multiphysics behind it. This study proposes a lattice Boltzmann (LB) model to study$\\text {CO}_2$desublimation on a cooled cylinder surface during CCC. In two-dimensional (2-D) simulations, various$\\text {CO}_2$desublimation and capture behaviours are produced in response to different operation conditions, namely, gas velocity (Péclet number$\\textit {Pe}$) and cylinder temperature (subcooling degree$\\Delta T_{sub}$). As$\\textit {Pe}$increases or$\\Delta T_{sub}$decreases, the desublimation rate gradually becomes insufficient compared with the$\\text {CO}_2$supply via convection/diffusion. Correspondingly, the desublimated solid$\\text {CO}_2$layer (SCL) transforms from a loose (i.e. cluster-like, dendritic or incomplete) structure to a dense one. Four desublimation regimes are thus classified as diffusion-controlled, joint-controlled, convection-controlled and desublimation-controlled regimes. The joint-controlled regime shows quantitatively a desirable$\\text {CO}_2$capture performance: fast desublimation rate, high capture capacity, and full cylinder utilization. Regime distributions are summarized on a$\\textit {Pe}$–$\\Delta T_{sub}$space to determine operation parameters for the joint-controlled regime. Moreover, three-dimensional simulations demonstrate four similar desublimation regimes, verifying the reliability of 2-D results. Under regimes with loose SCLs, however, the desublimation process shows an improved$\\text {CO}_2$capture performance in three dimensions. This is attributed to the enhanced availability of gas–solid interface and flow paths. This work develops a reliable LB model to study$\\text {CO}_2$desublimation, which can facilitate applications of CCC for mitigating climate change.

A model to predict the conditions for printability is presented. The model focuses on crack prevention, as well as on avoiding the formation of defects such as keyholes, balls and lack of fusion. Crack prevention is ensured by controlling the solidification temperature range and path, as well as via quantifying its ability to resist thermal stresses upon solidification. Defect formation prevention is ensured by controlling the melt pool geometry and by taking into consideration the melting properties. The model’s core relies on thermodynamics and physical analysis to ensure optimal printability, and in turn offers key information for alloy design and selective laser melting process control. The model is shown to describe accurately defect formation of 316L austenitic stainless steels reported in the literature.

A novel energetic material, Bifurazano [3,4-b: 3′,4′-f] furoxano [3″,4″-d] oxacyclo-heptatriene (BFFO), has been investigated regarding two aspects, namely its thermal decomposition and solidification characteristics. The DSC curves indicate that the peak temperature of BFFO decomposition process is 271.1 °C under the static pressure of 2 MPa and the volatility of BFFO at 120 °C is significantly lower than that of TNT, DNAN and DNTF. The solidification curve indicates that the solidification of BFFO is a basic linear uniform solidification process, which is obviously different from that of TNT, DNAN and DNTF. In addition, the facet of BFFO appears much smoother and fewer defects are observed in the solidified body after solidification via CT and SEM. The reduction in solidification defects also further improves the mechanical properties of BFFO, with significant improvements in compressive and tensile strength compared to DNTF, DNAN and TNT. In summary, BFFO is a potential melt-cast carrier explosive with excellent thermal stability, solidification characteristics and mechanical properties.