Unidirectional Solidification Research Articles

Parametric study of lotus-type pore shape in solid subject to Henry's laws at interfaces

Mechanisms of the length and maximum radius of lotus-type or single pores in ice or nonmetals satisfied by Henry's law at gas-liquid interfaces dissolved by a gas during unidirectional solidification are rigorously investigated and supported by a Table from algebraic predictions involving different dimensionless working parameters. Lotus-type porous materials characterized by directional properties have been often used as functional materials in food, biomedical, and micro- and nano-technologies. Following previous work taking into account solute amount and transport within the pore, and concentration boundary layers on the advancing solid-liquid interface and bubble cap, and the Young-Laplace equation and Henry's law at liquid-gas interfaces, the algebraic study further provides a Table for a quantitative and extensive understanding of different mechanisms of length and maximum radius. Dimensionless parameters include solute transport parameters of Henry's law constant, mass transfer coefficient, partition coefficient, solute gas amount in imposed ambient, and solute transport parameter, and fluid and thermal parameters of solidification rate, imposed gas pressure, hydrostatic pressure, and geometrical parameter of inter-pore spacing. The controlling of the shapes of lotus-type pores is achieved by a good comparison between predicted maximum diameter and inter-pore spacing during freezing of water dissolved by oxygen gas.

Formation mechanism of surface exudation in Cu-Sn alloy prepared by horizontal continuous unidirectional solidification

Formation mechanism of surface exudation in Cu-Sn alloy prepared by horizontal continuous unidirectional solidification

Solute segregation affected by transport properties during a bubble entrapment in upward solidification

Abstract The effects of transport properties on segregation of a dissolvable gas, for example, carbon dioxide in water in the presence of an entrapping bubble during upward unidirectional solidification is numerically investigated. Microporosity and inter-related solute segregation are two common defects detrimental to mechanical properties of components, especially to fatigue performance, strength and ductility. In this work, transport processes between the bubble, liquid and solid affected by mass, momentum, energy, and concentration Eqs. are solved by finite element schemes provided from the commercial COMSOL code. The results find that solute concentration in solid and liquid surrounding the pore increases with decreasing Henry's law constant and gravitational acceleration, and increasing surface tension and solid thermal conductivity. Solute gas concentration on the top free surface is insensitive to that in the pore rather than that in liquid and solid away from the pore. Apex cap becomes non-spherical affecting solidification rate and shape of the solidification front as ambient pressure at the top free surface and gravitational acceleration increase. Contact angle versus location of the solidification front predicted from this work and Abel's Eq. agrees well. Solute segregation encountered by pore formation is controllable.

Phase stability and unidirectional solidification in a Ni–Al bronze

CuAlFeNi alloys are considered very important from the commercial point of view to exhibit different phase transitions and properties, depending on the relationship among these phases. We investigated the stability of different formed phases after slow cooling, as well as after unidirectional solidification of the Cu-10.79 wt%Al-4.42 wt%Ni-3.67 wt%Fe alloy, establishing the effects of changes in the amounts of phases on material characteristics. The analysis was performed using optical microscopy, scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, hardness measurements, differential scanning calorimetry, and potentiodynamic polarization tests. The data revelated that the Ni and Fe increased the β phase stability. Obtained samples after unidirectional solidification exhibited a higher fraction of α phase when compared to the same alloy after slow cooling. It also was verified that the corrosion resistance is dependent on the position of the sample concerning the heat exchange surface.

Effect of Cooling Condition on Microstructure after Unidirectional Solidification of Cu-Ni-Si Alloys

In order to consider the effect of cooling conditions on microstructure formation during casting of Cu-Ni-Si alloy (Corson alloy), the microstructures of unidirectional solidification of the alloy were evaluated. Ingots of Corson alloy with several cooling conditions were prepared by Mizuta method, and microstructural observations and analysis of the distribution of added elements were performed. The primary and secondary dendrite arm spacings (P-DAS and S-DAS) became smaller with increasing cooling rate, and it was found that P-DAS and S-DAS can be accurately approximated by multiplier of cooling rate times temperature gradient, and by that of cooling rate, respectively. Between secondary dendrites, Si was enriched from the initial solidification zone to the final solidification zone, and Ni was almost constant around the initial solidification zone and enriched slightly around the final solidification zone. The Si enrichment was larger under the condition of lower cooling rate, which is expected to be closer to the equilibrium state. In this study, it was found for Corson alloy that DAS became bigger and Si enrichment between secondary dendrites was larger under the condition of lower cooling rate, and Ni enrichment was not affected by cooling rate.

Textural characterization of unidirectional solidification textures related to Cu–Au deposits and their implication for metallogenesis and exploration

Ten rock samples with unidirectional solidification textures (USTs) from nine Asian and Australian porphyry and intrusion-related Au deposits and prospects were investigated in terms of mineralization sequences, textural and paragenetic relationships, melt and fluid inclusion inventory, cathodoluminescence, and trace elements of UST quartz. Despite general similar structural appearance of the investigated UST sequences, each UST locality has its own specific textural features. We provide a structural classification of observed USTs that distinguishes equigranular and heterogranular USTs, which are subdivided according to the UST layer structure into straight, wavy, or contorted/brain-like type. In addition, there is the group of disturbed USTs comprising incompletely developed UST layers, and ductile- or brittle-fragmented UST sequences. Ti-in-quartz-based calculations revealed crystallization temperatures of UST quartz between 590 and 770 °C. Primary silicate melt inclusions found in four samples indicate that quartz crystallized initially from a silicate melt. In five samples, fluid inclusion “boiling” assemblages were observed, documenting brine-vapor phase separation due to pressure drop. In one case, the “boiling” assemblage is in primary inclusions and in the other cases the assemblages have been trapped in pseudosecondary inclusions in a later stage. Primary brine inclusions without coeval vapor-rich inclusions were identified in one sample only. Our results permit UST formation in either an open-system setting where fluids exsolved from UST crystallization are periodically released by fracturing (pressure drops) after the formation of each individual UST layer, or closed-system setting where the exsolved fluids are trapped because of lack of fracturing as long the UST sequence forms. Here, the closed-system model is introduced for the first time to describe the formation of layered quartz UST sequences in porphyry systems where the open-system setting seems to be not applicable. Nonetheless, quartz UST sequences are very important exploration vectors for porphyry systems. Six out of the ten UST samples are high-grade with up to 12 g/t Au. However, in the investigated cases, the Au mineralization postdates UST formation. At Oyut Ulaan and Tampang, the UST quartz formation is co-genetic with major Cu–Fe sulfide mineralization, whereas in the other localities the UST formation predates the sulfide mineralization. In any case, UST layer sequences clearly functioned as an outer carapace and, thus, as a chemo-physical trap of passing mineralizing fluids entering the UST structure and may offer a vector to the main stockwork mineralization, which might occur 100 to 200 m above the UST zone.

New insights into the effects of solidification process on the thermodynamic parameters and mechanical properties of CuAlBeNbNi shape memory alloy

In this work, the influence of the processes of unidirectional solidification and squeeze casting in microstructure, thermodynamic parameters and mechanical properties of CuAlBeNbNi shape memory alloy (SMA) was investigated. The results show that the unidirectional solidification process causes an increase in phase transformation temperatures and ductility, improves fracture toughness and reduces stress-induced martensite, residual stress and dissipated energy after load-unload tensile test of the CuAlBeNbNi alloy. The squeeze casting process, on the other hand, causes an increase in the density of grain boundaries, increasing the stress-induced martensite and the elastic energy of the direct martensitic transformation, while decreasing the impact toughness, increasing the residual deformation, the residual stress and the dissipated energy after the tensile cycle tests. These results indicate that the processes of unidirectional solidification and squeeze casting offer an alternative method to modify the thermodynamic parameters, mechanical properties, and microstructural properties of the CuAlBeNbNi SMA while keeping the composition constant. This study aims to fill the knowledge gap regarding the impact of solidification processes on the properties of Cu-based SMAs, specifically investigating CuAlBeNbNi SMAs.

Effect and mechanism of room temperature rolling, cryogenic rolling and heat treatment on mechanical properties and electrical conductivity of Cu-Ni-Si alloy with continuous directional solidification

Simultaneously improving the mechanical and electrical conductivity of copper alloys has become an important challenge. In this paper, columnar crystal Cu-Ni-Si alloy materials were prepared using continuous unidirectional solidification method, and the effects of room temperature rolling (RTR), cryogenic rolling (CR) and subsequent aging treatment on the microstructure, mechanical and electrical properties of C70250 copper alloy were investigated. The results show that the material has good tensile strength (886 MPa), elongation after break (5.2%) and electrical conductivity (42.4% IACS) when the columnar crystal C70250 copper alloy is cryogenic rolled with 95% depression rate and aged at 450 °C for 1 h. After severe rolling deformation, both RTR and CR C70250 copper alloy produce uniform fibrous structure. Large deformation CR can exhibit higher dislocation density compared with RTR C70250 copper alloy, high lattice distortion results in the transformation of the matrix into an amorphous structure, which has a very strong promotion effect on solute atom diffusion and recrystallization. The precipitation of the fine Ni2Si cluster phase with average size of ∼3.2 nm can be accelerated in a shorter aging time compared to RTR, while the uniform fibrous structure after CR can rapidly recrystallize to produce uniform ultra-fine grains with diameter of ∼550 nm. The strength of the cryogenic rolling alloy can significantly increase through precipitation strengthening, fine grain strengthening and dislocation strengthening. This provides a feasible strategy to improve the overall performance of Cu-Ni-Si alloys.

Cassiterite geochemistry and U–Pb geochronology of the Shihuiyao Rb–(Nb–Ta–Be–Sn) deposit, Northeast China: Implication for ore‑forming processes and mineral exploration

The Shihuiyao giant Rb deposit in association with Nb–Ta–Be–Sn occurs within the Southern Great Xing’an Range tin belt known for its Sn, W, Cu, Ag, and base-metal deposits. The trace element compositions of four types of cassiterites hosted in the granite, greisen, unidirectional solidification texture (UST) quartz layer, and the hydrothermal quartz vein, respectively (abbreviated as Cst-I to Cst-IV) were measured by laser ablation inductively coupled plasma mass spectrometry and electron probe microanalysis to establish chemical criteria for the application of cassiterite as a useful geological tracer mineral. In situ U–Pb dating of Cst-I, Cst-III, and Cst-IV yielded Tera–Wasserburg intercept ages of 150.3±5.2, 145.8±4.6, and 146.9±3.5 Ma, respectively. These ages are consistent with the previously published monazite and columbite U–Pb ages of 150.2–141.0 Ma for the Shihuiyao ore-bearing granites, indicating a genetic relationship between granite magmatism and Ta–Nb–Sn mineralization. The composition of the studied cassiterites within the whole magmatic–hydrothermal evolution process yields some petrographic dissimilarities and geochemical trends from xenothermal to epithermal environments, which can be used to fingerprint the fluid evolution of the Shihuiyao deposit. For example, the magmatic cassiterites (Cst-I and Cst-II) are strongly enriched in Ta and yield low Nb/Ta ratios compared to the Cst-IV cassiterites from shallow hydrothermal veins. The occurrence of wodginite-group minerals and the highest W concentrations in cassiterite from the UST quartz layers suggests that the main enrichment in W is primarily controlled by magmatic fluid exsolution during the magmatic–hydrothermal transition stage. Additionally, hydrothermal cassiterite is generally lighter in color and characterized by complex internal oscillatory zoning with alternate dark (Cst-IVa) and light (Cst-IVb) bands. Cst-IVa cassiterites have similar W, Nb, and Ta contents but much higher Ti contents compared to Cst-IIIb cassiterites related to primary magmatic fluid, whereas Cst-IVb cassiterites exhibit sharply decreasing W but elevated Ti contents, suggesting pulsed exsolution of magmatic ore‑forming fluids and the involvement of external fluid in a distal open-fluid systems during the late mineralization stage. Therefore, the chemical variations of cassiterites are not only robust tracers pointing to magmatic–hydrothermal centers but also effective in discriminating the primary source of alluvial cassiterite and evaluating its metallogenic potential during a natural heavy mineral survey, supporting the use of cassiterite as an indicator mineral for exploration targeting.

Influence of Microsegregation on the TiN Inclusions Formation Behavior in a K418 Superalloy during the Continuous Unidirectional Solidification Process

Controlling the formation behavior of inclusions during solidification is an effective approach to improve the purity of Ni-based superalloys. In this study, the effects of the microsegregation on the formation behavior of inclusions in the continuous unidirectional solidification (CUS) process were investigated. Three types of inclusions were found in revert and the CUS solidified K418 alloy: nitrides, oxides and SiC, with the nitrides as the dominant inclusions. With the application of the CUS process, the precipitation and growth behaviors of inclusions were significantly suppressed by the larger cooling rate, refinement of microstructure, and a reduction of microsegregation. Compared to the revert K418 alloy, the removal rates of the inclusion index and contents of N and O were 93, 84.1, and 57.7%, respectively in the CUS solidified K418 alloy at the withdrawal velocity of 27 mm/min. Numerical simulations based on a coupled microstructure-microsegregation-nucleation-growth model were carried out in order to verify the experimental results of the formation behaviors of inclusions during solidification. This study provided a theoretical and practical approach to the recovery of the revert K418 alloy.

Magmatic to hydrothermal evolution of the Gaogangshan Mo deposit, NE China: Mineralogical insights from quartz

Integrated study on cathodoluminescence (CL) textures and compositions of quartz is proven to be an effective way to reconstruct the ore-forming conditions and processes of porphyry system under subduction tectonic setting. However, little relevant research has been conducted on collision-type porphyry deposits. The Gaogangshan deposit in the northern Lesser Xing'an Range, NE China, consists of typical collision-type porphyry Mo mineralization related to Permo-Triassic granitic intrusions. Ore-forming process is recorded by multiple generations of quartz, including pre-ore stage quartz with unidirectional solidification texture (UST), early ore-stage quartz-molybdenite veins with K-feldspar alteration halos (Q1), late ore-stage quartz-sulfides veins with sericite alteration (Q2), and post-ore stage quartz veins (Q3) associated with calcite and fluorite. Cathodoluminescent textures, trace elements and fluid inclusions in quartz reveal physicochemical conditions, evolution of ore fluids and the Mo mineralization process. The UST quartz and Q1 veins are dominated by CL-bright homogenous and/or granular mosaic textures, containing more Ti concentrations (average = 35–42 ppm) than Q2 and Q3 veins. The molybdenite-bearing Q2 veins are dominated by CL-gray granular and zonal textures, displaying less CL intensity and lower Ti concentrations (average = 16 ppm) than early-stage quartz. The Q3 veins have the lowest CL-intensity and the lowest Ti concentrations (average = 2.5 ppm) among all quartz types. Three types of inclusions are identified in above quartz samples, including liquid–vapor aqueous inclusions, CO2-bearing liquid–vapor aqueous inclusions and halite-bearing multiphase aqueous inclusions. The ore-forming fluids in ore-stage Q1 and Q2 veins are dominated by large salinity variation (2.3–38.9 wt% NaCl equiv.), CO2-bearing (4.2–8.9 mol%) two-phase aqueous inclusions with vapor volumetric proportions of 30–65%. Intersections of fluid inclusion isochores with Ti-in-quartz isopleths yield quartz formation conditions of ∼2.2 kbar at ∼640℃ for UST quartz, ∼1.25 kbar at ∼510℃ for Q1, ∼1.0 kbar at ∼440℃ for Q2, and ∼0.37 kbar at ∼220℃ for Q3. The Gaogangshan porphyry Mo deposit formed at depths of 3.8 to 4.7 km.

In-situ characterization of double-diffusive convection during unidirectional solidification of a binary solution

ABSTRACT The work focuses on developing a detailed understanding of the effects of initial composition (C in ) and bottom cooling temperatures (TB ) on different characteristics of double-diffusive convection during unidirectional solidification of water-NH4Cl solution in a complete non-intrusive manner. The qualitative investigation, simultaneous quantification of transported parameters (composition and temperature) and fluid velocities associated with flow patterns are carried out using rainbow schlieren deflectometry, dual-wavelength interferometry and PIV (particle image velocimetry) technique respectively. The dependence of the characteristics of double-diffusive convection for different Cin and TB is explained on the basis of real-time whole-field investigation using a combination of aforementioned imaging techniques.

Comparison of Dynamical and Empirical Simulation Methods of Secondary Dendrite Arm Coarsening

The physical and mechanical properties of an entirely (wrought alloys) or partly (cast alloys) dendritically solidified alloy strongly depend on the secondary dendrite arm spacing (SDAS). The casting practice and the simulation of solidification need a usable but simple method to calculate the SDAS during and at the end of solidification as a function of the cooling rate. Based on many solidification experiments, a simple equation to calculate the SDAS (empirical method) is known to use the local solidification time, which can be obtained from the measured cooling curves (equiaxed solidification), or can be calculated from the temperature gradient and front velocity (directional solidification). This equation is not usable for calculating the SDAS during solidification. Kirkwood developed a semi-empirical method based on the liquid phase’s diffusion, which contains only one geometric factor that seems constant for different alloys. This equation contains some physical parameters that depend on the temperature, so the equation cannot be integral in closed form. In the present work, first, we show the effect of the curvature of the solid/liquid interface on the equilibrium concentrations and then the different processes of SDA coarsening. In our earlier paper, we demonstrated that using the empirical method, the final SDAS can be calculated with acceptable correctness in the case of four unidirectional solidification experiments of Al-7wt%Si alloy. The present work shows that numerically integrated Kirkwood’s equations used the known cooling curve; the SDAS can be calculated at the end and during solidification in good agreement with these experimental results. Compared to the two calculation methods, we stated that the correctness of the methods is similar. Still, the results of the solidification simulation (the microsegregation) will be more correct using the dynamical method. It is also shown that with the dynamical method, the SDAS can be calculated from any type of cooling curve, and using the dynamical method, it is proved that some different SDASs could belong to the same local solidification time.

Fluids and Melts at the Magmatic-Hydrothermal Transition, Recorded by Unidirectional Solidification Textures at Saginaw Hill, Arizona, USA

Abstract Fluid exsolution and melt evolution at the magmatic-hydrothermal transition are critical processes driving the metal enrichment of porphyry systems. Coeval fluid and melt inclusion assemblages in unidirectional solidification textures (USTs) at Saginaw Hill—a small, porphyry Cu system in southwestern Arizona—record a dynamic and repetitious process of fluid accumulation and release. The cores of quartz crystals throughout the UST bands host coeval silicate melt and brine inclusions but lack vapor-rich inclusions. This could indicate preferential expulsion of vapor and trapping of high-density brine during episodes of fracturing or the direct exsolution of single-phase high-salinity brine from the silicate melt. In contrast, the rims of UST quartz host abundant coeval brine and vapor inclusions, consistent with liquid-vapor immiscibility at lower pressures compared to the corresponding quartz cores. This transition from dominantly coeval silicate melt inclusions and brine in phenocryst cores to coeval brine and vapor in the rims suggests that the Saginaw Hill system underwent cyclic processes of fluid exsolution, accumulation, overpressure, and decompression at relatively stable temperatures (consistently ~650°C) during UST formation. Melt inclusion data indicate that the melt at this stage was highly fractionated and tended toward muscovite saturation. Metal concentrations in the brine were comparable to or higher than those in fluids reported in world-class porphyry Cu systems and were likely the result of both igneous fractionation and the high chloride content of the exsolved fluids. While limited in scale, Saginaw Hill provides evidence for processes that are predicted to occur at the magmatic-hydrothermal transition during the formation of large, well-mineralized porphyry systems.

Epitaxial growth and oxidation behavior of the NiCoCrAlYTa/Y2O3 coating on a nickel-based single-crystal superalloy blade tips, produced by electro spark deposition

The characteristics of the working surface are often related to the safety and longevity of the machine, therefore, various functional coatings are used to meet the special needs of particular components. Ni-based single crystal superalloy blade tips frequently suffer from oxidation, corrosion, and wear under harsh conditions. To improve these problems, the NiCoCrAlYTa/Y2O3 metal matrix composite coating was prepared by electro spark deposition. In this work, the microstructure and epitaxial growth behavior of the NiCoCrAlYTa/Y2O3 coating were investigated, and the oxidation resistance of the substrate and the coating were evaluated and compared. The coating showed ultra-fine columnar crystal structure. The diffusion between the substrate and the coating elements caused by the instantaneous high temperature generated by the electro spark deposition endowed the coating with extremely high metallurgical bonding strength. The ultra-high cooling rate and approximately one-dimensional unidirectional rapid solidification made the Y2O3 nanoparticles evenly dispersed in the coating and realized directional epitaxial growth. The NiCoCrAlYTa/Y2O3 coating exhibited excellent oxidation resistance compared to the substrate. Y2O3 nanoparticles changed the diffusion path of the elements and accelerated the formation of the Al2O3 film. The synergistic effect of ultra-fine microstructure and nanoparticles on the adhesion between the oxide scale and the coating was improved.

Dendrite fragmentation mechanism under forced convection condition by rotating magnetic field during unidirectional solidification of AlSi7 alloy

Forced convection and its effect on the microstructure evolution of an Al-7wt.%Si alloy during unidirectional solidification were studied experimentally. Under natural convection (gravity), columnar structures develop. However, under forced convection by activating a rotating magnetic field (RMF: 10 mT, 50 Hz), many equiaxed grains form in the half-radius region of the cylindrical sample, and a severe macrosegregation channel forms at the centre of the sample. Crystal fragmentation is regarded as the main source of equiaxed grains, but their formation mechanism and the fragment transport phenomenon are not fully understood. A mixed columnar-equiaxed solidification model with extension to consider two dendrite fragmentation mechanisms (capillary-driven and flow-driven), was used to reproduce the experiment with the objective to investigate the formation process of the microstructure and macrosegregation. Under the effect of the RMF-induced primary/secondary flow, the capillary-driven fragmentation mechanism, which is associated with dendrite coarsening, operates mainly in the peripheral region of the sample at a certain depth of the mushy zone. These fragments are difficult to be transported out of the (columnar dendritic) mushy zone. The flow-driven fragmentation mechanism associated with the interdendritic flow-induced re-melting of dendrites, operates mostly near the front of the mushy zone and/or around the central segregation channel. Some of these fragments can be transported out of the columnar tip region. In this case, a thin undercooled layer exists. Therefore, fragments can grow and become equiaxed grains. Some fragments are transported distally from the mushy zone into the bulk superheated region and are re-melted/destroyed there. The fragments, which continue to grow in the deep mushy zone or in the thin undercooled layer, are easily trapped by columnar dendrites, thereby competing with the growth of columnar dendrites to form a mixed columnar-equiaxed structure or even leading to a columnar-to-equiaxed transition.

Ice-templating hydrogels with high concentrations of cellulose nanofibers to produce architected cellular materials for structural applications

Ice-templated cellular materials made of entangled networks of slender cellulose nanocrystals (CNCs) or cellulose nanofibrils (CNFs) exhibit excellent specific physical properties but their mechanical properties are still insufficient: these biosourced systems cannot be used as structural materials, e.g., as cores of composite sandwich structures. To overcome this limitation, we ice-templated hydrogels with high concentrations of CNFs and CNCs by using a specific setup that enabled their unidirectional solidification. The microstructure and the mechanical properties of the freeze-dried foams were investigated using SEM, X-Ray nanotomography and compression tests, respectively. Increasing the content of nanofibers yielded to drastic shifts of (i) the foam microstructures from highly anisotropic (columnar with CNFs, lamellar with CNCs) to more isotropic ones (ii) the mechanical properties towards isotropy together with a significant increase of the foam stiffness, yield stress and absorbed energy. In addition, due to the high aspect ratio of the CNFs, CNF foams with elevated relative densities exhibit noteworthy specific mechanical properties.

Mechanisms leading to the formation of double-diffusive layers during unidirectional solidification of aqueous NH4Cl solution

Double diffusive layers (DDLs) are one of the flow patterns which arise due to the coupled effects of thermal and solutal gradients and find relevance in large-scale applications. We report observations of DDLs using unidirectional solidification of a binary mixture, which naturally introduces thermal and solutal buoyant flows. The convection rolls at the opposite sidewalls, having an opposite sense of rotation, ultimately merge to form the DDLs that expand throughout the breadth of the test chamber. Our research on exploring the mechanisms of DDLs uses a combination of nonintrusive techniques capturing full-field measurements in real-time to obtain insights on their evolution.

Growth of thallium-doped CsI/CsCl/KCl eutectics and their scintillation properties

In this study, Tl:CsI/CsCl/KCl ternary eutectic scintillators were grown using the vertical Bridgman–Stockbarger method by unidirectional solidification. The CsI and KCl phases were elongated along the growth direction, based on backscattered electron imaging (BEI) observations. The Tl:CsI scintillator phase grew as a matrix, which can be used to create optical waveguides for scintillation light. The expected Tl+ emission peak was observed at 550 nm under X-ray excitation. This emission was attributed to the self-trapped excitons perturbed by TI+ in Tl:CsI. The decay time of the Tl:CsI/CsCl/KCl eutectic was 285 ns, and its light output was estimated to be 10,800 photons/MeV.

Effect of Forced Melt Flow on Al–Si Eutectic-Alloy Microstructures

Al–Si eutectic alloys are industrially important; they play a significant role in the casting-manufacturing of most materials. The properties of the materials are governed by their microstructure, which can be tuned by adjusting the solidification process parameters. Herein, the effect of forced melt flow on the microstructure of an Al–Si eutectic alloy during unidirectional solidification was investigated experimentally. Al–12.6-wt%-Si alloy samples were solidified in a vertical Bridgman-type furnace equipped with a rotating magnetic inductor to induce flow in the melt. The samples were subjected to different magnetic induction conditions during the solidification experiments. The diameter of the samples was 8 mm, and their length was 120 mm. The eutectic alloy samples were solidified unidirectionally at a growth rate of v ≈ 0.1 mm/s and a temperature gradient of G ≈ 6 K/mm. The inter-lamellar distances (λ), lengths, and orientation angles of the Si lamellae were investigated using new measurement methods. The experimental results reveal that applying the rotating magnetic field (RMF) during the solidification has a distinct effect on the microstructure of Al–Si eutectic alloys. Indeed, the RMF refines the eutectic structure, reduces the interlamellar distances, and increases the diversity of the Si lamella angle’s orientations. However, the successive stirring process has a negligible effect on the lengths and angles of Si lamellae.