A series of cost effective Co-free AlxCrCuFeNi2 high entropy alloys were developed, following the valence electron concentration rule. The solidification microstructure in these alloys showed some ...anomalies that were rarely seen in other high entropy alloys or multi-component alloys. Specifically, submicron rod-like microstructures existed in the eutectic alloy in spite of the high volume percentage of the rod-like phase; sunflower-like microstructures existed in the hyper-eutectic alloys, with 200nm sized spinodal decomposed seed particles densely distributed in the disk floret.
The microstructure of the B1-type TiC formed during solidification and its mechanical properties were investigated using arc-melted Fe–Ti–C ternary alloys. The TiC formed at relatively high ...temperatures in the liquid as the primary phase exhibited a dendritic shape. With decreasing temperature and/or decreasing Ti and C content in the liquid, the morphology of the TiC changed to a cubic shape with a {001}TiC habit plane, a plate shape with a {011}TiC habit plane, and a needle shape with a preferential growth direction of TiC. The morphology of the TiC was characterized by the anisotropy of its surface energy and its growth rate. The cubic shape with a {001}TiC habit plane was formed as a result of the {001}TiC surface exhibiting the lowest surface energy among the TiC surfaces. However, the plate shape with a {011}TiC habit plane and the needle shape with a TiC preferential growth direction likely formed because the slowest and fastest growth rates corresponded to the TiC and TiC directions, respectively. At room temperature, the alloy with dendritic TiC was fractured in the elastic deformation region because TiC exhibited no plastic deformation. However, the results obtained at 800°C suggested that the TiC exhibited plastic deformability and that the alloy with the dendritic TiC was also plastically deformed.
Solid‐state lithium‐metal batteries constructed by in‐situ solidification of cyclic ether are considered to be a critical strategy for the next generation of solid‐state batteries with high energy ...density and safety. However, the poor thermal/electrochemical stability of linear polyethers and severe interfacial reactions limit its further development. Herein, in‐situ ring‐opening hybrid crosslinked polymerization is proposed for organic/inorganic hybrid polymer electrolyte (HCPE) with superior ionic conductivity of 2.22 × 10−3 S cm−1 at 30 °C, ultrahigh Li+ transference number of 0.88, and wide electrochemical stability window of 5.2 V. These allow highly stable lithium stripping/plating cycling for over 1000 h at 1 mA cm−2, which also reveal a well‐defined interfacial stabilization mechanism. Thus, HCPE endows assembled solid‐state lithium‐metal batteries with excellent long‐cycle performance over 600 cycles at 2 C (25 °C) and superior capacity retention of 92.1%. More importantly, the proposed noncombustible HCPE opens up a new frontier to promote the practical application of high safety and high energy density solid‐state batteries via in‐situ solidification.
A novel design of a hybrid crosslinked solid polymer electrolyte (HCPE), which is prepared by in situ solidification at room temperature, is reported. Lithium metal cells with this HCPE have the advantages of high ionic conductivity (2.22 × 10−3 S cm−1 at 30 °C), high electrochemical window (5.2 V), high lithium‐ion transference number (0.88), and long lifetime (>600 cycles) at room temperature (25 °C).
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.
Effect of Ta addition on solidification characteristics of CoCrFeNiTax (x = 0.1–0.7) eutectic high entropy alloys were investigated. With increasing Ta content, CoCrFeNiTax alloys changed from ...hypoeutectic alloys with primary γ phase to eutectic alloy (x = 0.43) and to hypereutectic alloys with primary Laves phase. Consequently, Ta content in primary phase significantly increased, while the content of Ta element in γ/Laves eutectic phases slightly decreased. Meanwhile, the solidification path and solidification characteristic temperatures of CoCrFeNiTax alloys both agreed with typical binary eutectic phase diagram, and obvious microsegregation of Ta element was only found in CoCrFeNiTa0.1 alloy. Furthermore, the contents of Co, Cr, Fe and Ni elements in primary phases and distribution behaviors of Co, Cr, Fe and Ni elements were both different in CoCrFeNiTax alloys, which indicated that CoCrFeNiTax alloys cannot be simplified as (CoCrFeNi)–Ta pseudo binary system when analyzing distribution behaviors of Co, Cr, Fe and Ni elements.
•Solidification characteristics of CoCrFeNiTax alloys were studied.•CoCrFeNiTax alloys divided into hypoeutectic, eutectic and hypereutectic alloys.•Solidification path of CoCrFeNiTax alloys obeyed binary eutectic phase diagram.•Distribution behaviors of Cr and Fe elements were similar.•Distribution behaviors of Co and Ni elements were different in hypereutectic alloys.
Metastable solidification mechanisms and micromechanical property modulations of rapidly crystallizing peritectic Si66.7Ni33.3 alloy were systematically investigated by glass fluxing and arc melting ...techniques. Glass-fluxed samples were undercooled up to 230 K, and the solidification microstructures consisted of Si, NiSi2 and NiSi phases. As the undercooling rose, primary Si phase grew faster along with the enhancement of volume fraction and the morphology transitioned from lamellar structure to dendritic structure. Meanwhile, the thickness of lamellar Si phase basically remained the same, and its length and width decreased gradually. The subsequent peritectic reaction became more intense and peritectic NiSi2 phase became narrower. The 123 K was the critical undercooling for the abrupt rise of eutectic growth velocity, the morphology transition of regular eutectic in the interdendritic gap of NiSi2 to the anomalous eutectic, and the sudden drop of the sample microhardness. The solute Ni content in NiSi2 and NiSi phases increased linearly with a rise in the undercooling, indicating the substantial expansion of solid solubility and the occurrence of an evident solute trapping phenomenon. For arc-melted samples with 8 mm diameter, the solidification microstructure mainly appeared as primary lamellar Si phase surrounded by peritectic NiSi2 phase plus eutectic (NiSi + NiSi2) phase, and the farther away from the sample bottom the smaller the undercooling and the higher the sample microhardness. As the sample diameter decreased to 2 mm, peritectic NiSi2 phase directly nucleated in the sample bottom and the microstructure composition in other regions resembled the large samples. The Si phase possessed lamellar and dendritic structures in the sample top and middle regions, respectively. Moreover, a maximum microhardness was determined in the lower middle region. The research has both scientific and industrial relevance, offering insights that could be applicable to the development and processing of complex alloy systems.
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•Metastable solidification kinetics of undercooled Si66.7Ni33.3 peritectic alloy is investigated.•Three-dimensional morphologies of primary Si phase at various undercoolings are characterized.•An obvious solute trapping phenomenon of two intermetallic compound phases is observed.•Micromechanical properties of undercooled Si66.7Ni33.3 peritectic alloy are experimentally measured.•Rapid solidification mechanisms of Si66.7Ni33.3 alloy droplets placed on a chilling surface are studied.
Cracking during solidification is a serious defect in castings and welds. When solidification shrinkage and thermal contraction of the semisolid and its surrounding solid are obstructed, tensile ...deformation can be induced in the semisolid to cause cracking along grain boundaries that are not fed with sufficient liquid. A criterion for cracking was derived, focusing on events occurring at the grain boundary including separation of grains from each other, lateral growth of grains toward each other, and liquid feeding between grains. An index for the susceptibility of an alloy to cracking during solidification was also proposed, that is, |dT/d(fS1/2)| near (fS)1/2=1, where T is temperature and fS the fraction solid in the semisolid. The index affects: (a) the lateral growth rate of two neighboring grains toward each other to bond together to resist cracking, and (b) the length of the grain-boundary liquid channel through which feeding has to occur to resist cracking. The index was verified with experimental data in casting and welding of Al alloys.
•Microstructures at a wide range of solidification cooling rate were investigated.•The shapes of γ′ precipitates exhibit irregular, cuboidal and spherical patterns.•γ′ size decreases with cooling ...rate in cellular and dendritic growth conditions.•γ′ is obvious smaller in crystallizing cores than that in interval regions.
The evolution of microstructures at a wide range of solidification cooling rate in a Ni-based superalloy was investigated by employing conventional casting, spray casting and melt spinning processes. Depending on solidification cooling rate, microstructures sequentially show planar, cellular, dendritic, the dendritic growth suppressed features (in melt spinning process) and the shapes of γ′ precipitates progressively exhibit irregular (planar and cellular growth), cuboidal (dendritic growth) and spherical (dendritic growth suppressed) patterns. Moreover, in dendritic growth conditions, γ′ shapes experience irregular cuboidal, regular cuboidal and near cuboidal patterns with increasing cooling rate. γ′ precipitates in dendritic cores show more and less regular morphology than those in interdendritic regions in lower and higher cooling rate range, respectively. The size scale of γ′ precipitates decreases with solidification cooling rate in cellular and dendritic growth conditions and γ′ precipitates are obviously smaller in crystallizing (cellular or dendritic) cores than those in interval regions.
The microsegregation in single-crystal nickel-base superalloys, which may result in many undesired precipitated phases, can be effectively reduced by rapid solidification. A new microsegregation ...model for rapid solidification multicomponent alloys was developed in this paper to predict the microsegregation in the single-crystal superalloys of laser rapid directional solidification and study the influence of processing parameters on the microsegregation behavior. To verify the predicted accuracy of the present model, the concentration profiles and microsegregation ranges under different processing conditions were examined and compared with those calculated by different models. Compared with previous models, this multicomponent model not only has definite physical meaning but also takes nonequilibrium solidification and dendritic tip undercooling into account. Therefore, it is suitable for a wide range of solidification conditions and can obtain better predicted results for complex multicomponent alloys. Moreover, although the microsegregation behavior depends primarily on the solidification velocity, a high temperature gradient also contributes to reducing the microsegregation. Consequently, the microsegregation can be effectively controlled by using a set of processing parameters that can obtain high temperature gradient and solidification velocity. Such a model contributes to the control of the microsegregation while determining relevant processing windows for the preparation of superalloy components using a controlled single-crystal laser processing.
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