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Purpose: Producing superior-quality ductile cast iron demands the use of various intricate inoculants. In addition to iron and silicon, these materials also include alloying elements like calcium, barium, cerium, bismuth and zirconium. These elements are effective in minimizing carbide solidification and enhancing the formation of eutectic cells, thereby resulting in improved cast iron quality. Design/methodology/approach: This article discusses the findings of an investigation on how various inoculants impact critical thermal analysis parameters such as undercooling, recalescence and their correlation with the nucleation of graphite nodules and shrinkage tendency. Findings: For the study, five distinct inoculants with varying active components in their chemical composition were utilized. The particular formulation of the inoculant has a notable impact on the extent of undercooling during the solidifying process of ductile cast iron. Investigation indicates that incorporating inoculant reduces the temperature at which austenite dendrites form and raises the eutectic freezing temperature. Upon analyzing the microstructure, it is found that the inclusion of inoculation led to a rise in the nodule count from 103 to 272 nodules. Originality/value: An increased graphite factor, which denotes the growth of graphite nodules during the subsequent stage of the eutectic reaction, supports the benefits of inoculation. Ce and Bi-inoculation have increased the growth of graphite nodules in the cast area during solidification compared to other inoculant formulations. This enhanced production helps in decreasing the size of macroporosity. [ABSTRACT FROM AUTHOR]

As one of the representative patterns in nature and laboratory experiments, dendritic structures control the properties of a broad range of advanced materials. Dendrites arise during different phase and structural transformation processes. Generally, the formation of dendritic structures are stipulated by transport processes in bulk phases, together with thermodynamic properties and kinetic phenomena at the phase interfaces. The formation of a dendritic microstructure under the influence of external fields (electromagnetic and gravitational) is considered in this review. These fields involve the liquid and gaseous phases in a forced convective flow, causing the transfer of energy and matter in addition to the usual conductive (diffusion) transport. The formulated model takes into account rapid solidification from an undercooled liquid phase as well as intermediate and low growth velocities of dendritic crystals in pure one-component systems extended to binary mixtures and alloys. The areas of undercooling are identified, in which the influence of convection caused by the electromagnetic and/or gravitational field is most noticeable. The solidification regimes (from the diffusion-limited mode to the thermally and kinetically controlled mode) are reviewed in connection with the different liquid flow velocities that dictate various boundary conditions (conductive and convective) on the surface of growing crystals. A comparison of model predictions with experimental data and computational results provides the grounds for a discussion about the applicability of the formulated model to interpreting known and unexpected phenomena in the formation of a crystalline structure. By changing the power of the considered fields or reducing them almost to zero (for instance, in microgravity), it is possible to control the dispersion of a dendritic microstructure, as well as separate accompanying phases (eutectic, peritectic, monotectic, intermetallic phases, etc.) during the solidification of materials and, in the general case, during phase transformations. [ABSTRACT FROM AUTHOR]

The development of sector zoning in clinopyroxene is attributed to the influence of crystallisation kinetics imposed by magma undercooling (ΔT) and may reflect variations in magma cooling histories. Yet, the degree of compositional variations between sectors has not been explored as a potential recorder of crystallisation dynamics. Here, we investigate the distribution of major, minor, and trace elements between hourglass {−1 1 1} and prism { h k 0} sectors in clinopyroxene with distinct pre-eruptive histories at Mt. Etna, Italy. We analyse sector-zoned clinopyroxene crystals ranging in size from sub-mm to cm (i.e., microphenocrysts, phenocrysts, and megacrysts), from eruptions fed by the central conduits of the volcano (1669 and 2002–03 flank eruptions) and eruptions fed by eccentric dykes which bypass the central conduits, tapping deeper magma storage regions (1974 and 2002–03 flank eruptions). We focus on Cr-rich mantle zones, which crystallised upon eruption triggering mafic rejuvenation and are ubiquitous across our sample set. With decreasing crystal size (i.e., increasing ΔT), tetrahedral aluminium is more strongly partitioned between prism and hourglass sectors. This promotes the uptake of rare earth elements (REE) and high field strength elements (HFSE) into prism relative to hourglass sectors. Combining relative degrees of sector enrichment with ΔT estimates, we propose magma recharge, mush remobilisation and the onset of magma ascent imposed slightly higher ΔT in 1974 than in 2002–03 eruptions at Mt. Etna. Enhanced ΔT in 1974 could be related to vigorous mixing and rapid transport of magma with limited storage, resulting in crystals of smaller sizes. Crystal size populations vary across eruptions, but crystals within a given population (e.g., phenocrysts) return similar calculated ΔT and REE + HFSE sector enrichments, implying connectivity between magmatic environments in the mush system. We show that the magnitude of sector zoning in clinopyroxene can be employed to explore subtle differences in pre-eruptive dynamics in volcanic systems. As an example, we explore sector enrichment in clinopyroxene phenocrysts from the 2021 eruption at La Palma (Canary Islands) and megacrysts from Roman era activity at Stromboli (Italy). Results highlight the role of dynamic mixing and mush remobilisation before eruption in mafic alkaline settings and suggest changes in magma composition across alkaline systems influence clinopyroxene chemistry but do not influence sector enrichment. [ABSTRACT FROM AUTHOR]

This work examined the performance of self-heating concrete under laboratory thermal conditions and outdoor real-time conditions during the fall and winter seasons. Snow-melting and freeze–thaw performance of low-temperature phase change materials (PCM) incorporated self-heating concrete slabs in various scales were evaluated. PCM exhibited high enthalpy of fusion (ΔHf≈170–180 J/g), long-term thermal stability, and desirable supercooling. The experimental program included (1) optimization of concrete mix designs for maximum PCM incorporation, (2) characterization of thermal properties of PCM-mortar specimens using longitudinal guarded comparative calorimetry (LGCC), and (3) large-scale PCM concrete slabs in outdoor conditions to evaluate the real-time thermal performance against freeze–thaw events and snow-melting efficiency. Two different approaches were used to incorporate PCM in concrete: (1) submersion of liquid PCM in porous lightweight aggregates (PCM-LWA); and (2) microencapsulated PCM (MPCM). Both PCM-LWA and MPCM concrete not only exhibited promising snow-melting capabilities but also lowered the number of freeze–thaw cycles during cold seasons. PCM-LWA concrete performed better in decreasing the number of freeze–thaw (F-T) cycles due to the undercooling phenomenon created by the LWA pore network confinement pressure, allowing gradual latent heat release; the undercooling phenomenon in PCM-LWA results in phase transformation in a wider low-temperature range (i.e., 3.94°C to −13.04°C). Therefore, the PCM-LWA concrete was effective in melting snow within a wider range of low temperatures. MPCM concrete was found to provide a rapid melting capability during a snowfall event due to its "one-shot" heat release phenomenon. Both LWA-PCM and MPCM concrete slabs demonstrated promising heat response and snow-melting capability. Snowfall and freeze–thaw cycles occur frequently during winter seasons in North American regions with cold climate, resulting in snow accumulation on concrete roads and flatworks as well as concrete freeze–thaw damage. In this paper, a "self-heating" concrete was developed via incorporation of low-temperature phase change material (PCM), and its promising snow removal and freeze–thaw improvements were validated. The self-heating concrete can be used to construct pavements, driveways, bridge decks, and any other types of flatworks. When the ambient temperature falls to ∼0°C , PCM will release desirable amounts of heat energy (ΔHf=170–180 J per g of PCM added) by changing its phase from liquid to solid. As a result, the accumulated snow and ice melts at a gradual pace. In addition, heat release from the incorporated PCM lowers the number of freeze–thaw cycles, improving freeze–thaw performance of concrete made elements in cold regions, which in turn improves concrete durability and service life by minimizing the susceptibility to freeze–thaw scaling and spalling. [ABSTRACT FROM AUTHOR]

Al 2 O 3 /ZrO 2 eutectic bulks (20 mm in diameter) with different Y 2 O 3 contents (0–4.5 mol %) were grown using the conventional casting method. Variations in the microstructural characteristics and colony tip growth behavior caused by Y 2 O 3 addition in the central equiaxed grain zone were investigated. As Y 2 O 3 was added to the Al 2 O 3 /ZrO 2 binary eutectic, except for a decrease in colony size, the colony tip radius reduced drastically and then increased slightly. Colony growth behavior can be well predicted using the Lipton–Glicksman–Kurz (LGK) model. A critical Y 2 O 3 content (0.5–1.1 mol%) exists below which the eutectic colony growth is accelerated owing to the Y 2 O 3 addition, but slowed down otherwise. However, the average interphase spacing and ZrO 2 rod diameter inside the colonies varied with Y 2 O 3 content, converse to the growth rate. [ABSTRACT FROM AUTHOR]

The Invar alloy has excellent properties, such as a low coefficient of thermal expansion, but there are few reports about the rapid solidification of this alloy. In this study, Invar alloy solidification at different undercooling (ΔT) was investigated via glass melt-flux techniques. The sample with the highest undercooling of ΔT = 231 K (recalescence height 140 K) was obtained. The thermal history curve, microstructure, hardness, grain number, and sample density of the alloy were analyzed. The results show that with the increase in solidification undercooling, the XRD peak of the sample shifted to the left, indicating that the lattice constant increased and the solid solubility increased. As the solidification of undercooling increases, the microstructure changes from large dendrites to small columnar grains and then to fine equiaxed grains. At the same time, the number of grains also increases with the increase in the undercooling. The hardness of the sample increases with increasing undercooling. If ΔT ≥ 181 K (128 K), the grain number and the hardness do not increase with undercooling. [ABSTRACT FROM AUTHOR]

A transition of dendrite growth kinetics from stable hcp to metastable fcc phases was observed for refractory Re95W5 alloy in an electrostatic levitation state, which attained a liquid undercooling up to 872 K (0.26TL). Stable hcp dendrite dominated in the single recalescence for pure Re in the whole of its undercooling regime, but prevailed for Re95W5 alloy only in the specific range of 159–867 K undercooling. The rapid dendrite growth velocity displayed a power-law relationship with the degree of undercooling. Once the refractory alloy melt was undercooled beyond 867 K undercooling, metastable fcc dendrite grew primarily from the liquid phase in the first recalescence, which was followed by a complete 'fcc to hcp' solid-state transformation in the second recalescence. An abrupt change of growth kinetics took place to depress the dendrite growth velocity drastically from 41.8 m·s−1 for stable hcp phase at 867 K undercooling to 10.9 m·s−1 for metastable fcc phase at 872 K undercooling. [ABSTRACT FROM AUTHOR]

Thermobarometry provides a critical means of assessing locations of magma storage and dynamics in the lead-up to volcanic eruptions and crustal growth. A common approach is to utilise minerals that have compositions sensitive to changes in pressure and/or temperature, such as clinopyroxene, which is ubiquitous in mafic to intermediate magmas. However, clinopyroxene thermobarometry may carry significant uncertainty and require an appropriate equilibrium melt composition. In addition, the degree of magma undercooling (Δ T) affects clinopyroxene composition and zoning, with common sector zoning potentially obfuscating thermobarometry results. Here, we use a set of crystallisation experiments on a primitive trachybasalt from Mt. Etna (Italy) at Δ T  = 25–233 °C, P = 400–800 MPa, H2O = 0–4 wt % and fO2 = NNO + 2, with clinopyroxene crystals defined by Al-rich zones (prisms and skeletons) and Al-poor zones (hourglass and overgrowths) to assess common equilibrium models and thermobarometric approaches. Under the studied conditions, our data suggest that the commonly applied Fe–Mg exchange (cpx-meltKdFe–Mg) is insensitive to increasing Δ T and may not be a reliable indicator of equilibrium. The combined use of DiHd (CaMgSi2O6 + CaFeSi2O6) and EnFs (Mg2Si2O6 + Fe2Si2O6) models indicate the attainment of equilibrium in both Al-rich and Al-poor zones for almost all investigated Δ T. In contrast, CaTs (CaAl2SiO6) and CaTi (CaTiAl2O6) models reveal substantial deviations from equilibrium with increasing Δ T , particularly in Al-rich zones. We postulate that this reflects slower diffusion of Al and Ti in the melt compared with Ca and Mg and recommend the concurrent application of these four models to evaluate equilibrium between clinopyroxene and melt, particularly for sector-zoned crystals. Thermobarometers calibrated with only isothermal–isobaric experiments closely reproduce experimental P–T at low Δ T , equivalent to natural phenocrysts cores and sector-zoned mantles. Models that also consider decompression experiments are most accurate at high Δ T and are therefore suitable for outermost phenocryst rims and groundmass microlites. Recent machine learning approaches reproduce P–T conditions across all Δ T conditions. Applying our experimental constraints to sector-zoned microphenocrysts and groundmass microlites erupted during the 1974 eccentric eruption at Mt. Etna, we highlight that both hourglass and prism sectors are suitable for thermobarometry, given that equilibrium is sufficiently tested for. The combination of DiHd, EnFs, CaTs and CaTi models identifies compositions closest to equilibrium with the bulk melt composition, and results in smaller differences in P–T calculated for hourglass and prism sectors compared with applying only DiHd and EnFs equilibrium models. This provides a framework to assess crystallisation conditions recorded by sector-zoned clinopyroxene crystals in mafic alkaline settings. [ABSTRACT FROM AUTHOR]

The Yalguba Ridge volcanic rocks form part of the Middle Paleoproterozoic (ca. 1.97 Ga) volcano-sedimentary sequence within the Karelian Craton in the Fennoscandian Shield. Yalguba variolitic textures are known worldwide and have been previously considered to originate from liquid immiscibility. The present study reveals two new variolite types recognized in the Yalguba sequence: (1) Variolites with unzoned varioles have distinct chemical and mineralogical compositions of varioles and matrix that support an origin by liquid immiscibility. They were recognized in quenched zones of pillows, so it might be assumed that melt separation caused by liquid immiscibility occurred before magma emplacement. The difference from the previously described variolites lies in the variole microtexture and might be caused by the various cooling conditions. (2) Spherulitic variolites have varioles composed of andesine–oligoclase spherulites embedded in the cryptocrystalline matrix with oligoclase–anorthoclase composition, thus the variole and matrix have similar chemical and mineralogical composition. The mineralogical and textural features of these variolites suggest that the spherulites have a primary magmatic origin due to the rapid cooling of superheated magma. The variety of variolitic textures in the Yalguba section might be caused by the different H2O saturation of parental magma and cooling conditions. [ABSTRACT FROM AUTHOR]

The present analysis addresses the solidification and thermodynamic parameters involved during the solidification of aluminum (Al)-based alloys as presented in the literature using different systems viz., binary aluminum-boron (Al-B) and aluminum-titanium (Al-Ti) systems, ternary aluminum-titanium-boron (Al-Ti-B) and aluminum-titanium-carbon (Al-Ti-C) systems, as well as taking into consideration the silicon-titanium-aluminide (Si-TiAl3) interaction in Al-based alloys containing Si. The analysis is supported by recent metallographic evidence obtained by the authors on A356.2 alloys. The sections on thermodynamic aspects cover the different models proposed concerning nucleation and growth on a newly formed Al grain. The value of the recalescence parameter reduces gradually with the increase in the Ti added. At a level of 0.20 wt%, this parameter becomes zero. If the concentration of grain refiner exceeds a certain amount, the grain size becomes minimal. Another parameter to be considered is the interaction between the grain refiner and traces of other metals in the base alloy. For example, Al-4%B can react with traces of Ti that may exist in the base alloy, leading to the reaction between boron and titanium to form titanium diboride (TiB2). Grain refinement is achieved primarily with TiB2 rather than aluminum diboride (AlB2), or both, depending on the Ti content in the given alloy. [ABSTRACT FROM AUTHOR]

In this study, a series of Bridgman casting experiments were conducted to study the physical processes occurring in 2D grain selectors with different geometric parameters. The corresponding effects of the geometric parameters on grain selection were quantified by using an optical microscopy (OM) and a scanning electronic microscopy (SEM) equipped with electron backscatter diffraction (EBSD) function. Based on the results, the influences of the geometric parameters of the grain selectors are discussed, and an underlying mechanism accounting for the experimental results is proposed. The critical nucleation undercooling in the 2D grain selectors during grain selection was also analyzed. [ABSTRACT FROM AUTHOR]

The present article addresses solidification parameters, and includes analyses of the macrostructure and microstructure in the light of the results obtained from the thermal analysis, from which it is possible to conclude that undercooling (TS) and recalescence (TR) temperatures increase with the initial increase in titanium (Ti) concentration. If the concentration reaches approximately 0.25%, a rapid decrease in these temperatures is observed. Thereafter, the temperatures increase again with the further increase in Ti concentration, and eventually become constant. These temperatures also vary depending on the superheating and casting temperature. The ∆T parameter (i.e., TS − TR) decreases with the Ti concentration and, from a concentration of around 0.20% Ti, this parameter becomes zero. The grain size decreases with the Ti concentration. If the concentration exceeds about 0.20%, the grain size becomes the minimum. Another parameter to be considered is the interaction between the grain refiner and the traces of other metals in the base Al alloy. For example, Al-4%B can react with traces of Ti that may exist in the base alloy, leading to the reaction between boron (B) and Ti to form TiB2. Grain refinement is achieved primarily with TiB2 rather than AlB2, or both, depending on the Ti content in the given alloy. [ABSTRACT FROM AUTHOR]

The Sn-8.8 wt. % Zn eutectic alloy was produced by using casting furnace and vacuum melting furnace. Then cast alloys were directionally solidified upwards with a constant temperature gradient (G=4.16 K/mm) at different solidification rates (V=8.3-166.0 μm/s) in a Bridgman type controlled directional solidification furnace. The undercooling (ΔT) values are calculated with the Jackson-Hunt model by using the solidification rate, eutectic spacing (λ) and system parameters (K1 and K2). At a constant temperature gradient (G=4.16 K/mm) with the increasing of solidification rate from 8.3 μm/s to 166.0 μm/s, undercooling increased from 0.87 K to 3.89 K. At minimum undercooling of 0.87 K, the rod eutectic spacing is obtained 3.22 μm while the eutectic spacing is obtained 0.72 μm at the 3.89 K. The results were compared with the literature. [ABSTRACT FROM AUTHOR]

In the realm of undercooled eutectic alloys, the nucleation (i.e., copious vs. single) and the growth (i.e., coupled vs. decouple) modes, particularly the formation of anomalous eutectics, remain subjects of intense debate. This study delves into the crystallographic orientation relationships (ORs) during rapid solidification of an undercooled Co-24 at.% Sn eutectic alloy, where the high-temperature eutectic phases (β-Co 3 Sn 2 and α-Co) persist to room temperature. A significant finding is the consistent observance of the same eutectic OR, i.e., 11 2 ̅ 0 β − Co 3 Sn 2 // 1 1 ̅ 1 α − Co and 0001 β − Co 3 Sn 2 // 110 α − Co , across various undercooling conditions from low to high and eutectic morphologies from lamellar to anomalous. This consistency underscores a unified growth mode of coupled eutectic growth. Furthermore, the observance of twin OR, i.e., 11 2 ̅ 1 < 11 ̅ 26 > , 11 2 ̅ 2 < 11 23 ̅ > or 11 2 ̅ 4 < 22 43 ̅ > , between β-Co 3 Sn 2 phases in diverse eutectic colonies, spanning from low to intermediate undercooling, and would also be the case of high undercooling, reinforces a single nucleation mode except under exceedingly low undercooling. Building on these insights, the anomalous eutectic colonies are suggested to be formed from a single origin where coupled eutectic growth of eutectic seaweeds or eutectic dendrites instead of dual origins. This study not only illuminates the underlying mechanisms of rapid solidification in undercooled eutectic alloys but also paves the way for innovative microstructure modulation strategies. [Display omitted] • The 11 2 ̅ 0 β − Co 3 Sn 2 // 1 1 ̅ 1 α − Co , 0001 β − Co 3 Sn 2 // 110 α − Co eutectic OR is followed independently with undercooling and microstructures. • Twin ORs are obeyed between β-Co 3 Sn 2 in different eutectic colonies except for very low undercooling. • The single nucleation mode is the case if undercooling is not very low and the coupled eutectic growth mode is followed. • Anomalous eutectics are formed from coupled eutectic growth but not uncoupled dendrite growth. [ABSTRACT FROM AUTHOR]

Multi-principal element alloys (MPEAs) have attracted growing attention owing to the vast compositional field and the comprehensive properties. In this work, Fe 7 (CoNi) 77 B 16 MPEA was undercooled by vacuum melting furnace with low (61 K, 95 K), medium (115 K, 148 K), and high undercoolings (200 K). The maximum growth velocity of the alloy was 0.21 m/s due to the sluggish kinetics effect. The regular eutectic transformed to anomalous eutectic and the primary dendrite refined from 9.1 μm to 3.5 μm with the increase of undercooling. Meanwhile, the phase selection behavior at high undercooling was observed between the stable (Fe, Co, Ni) phase and the metastable (Fe, Co, Ni) 23 B 6 phase. The hardness of primary phase and compressive strength of the undercooled MPEAs were increased to 952.19 HV and 2061.72 MPa, which is much higher than the as-cast alloy. The enhancement of the mechanical properties was attributed to microstructure evolution. The decrease in plasticity resulted from the increasing volume fraction of brittle intermetallic phases. This study helps to theoretically understand the solidification mechanism of the Fe-Co-Ni-B MPEAs and provides a promising way to enhance the mechanical properties of the novel MPEAs. • The growth velocity of primary dendrite is determined. • Regular eutectic transforms to anomalous eutectic. • The microstructure refines with the increase of undercooling. • Phase selection occurs at high undercooling. • Mechanical properties enhance due to non-equilibrium solidification. [ABSTRACT FROM AUTHOR]

The mechanism of grain refinement in undercooled Ni 3 Ga melts was investigated. An in situ diagnosis of the dendrite growth velocity using a high-speed camera indicates direct crystallization of the Ni 3 Ga compound and disorder trapping at a critical undercooling of 68 K and 120 K, respectively. An EBSD analysis shows a grain-refined microstructure for samples with undercoolings of 120 K and 148 K in contrast to a coarse-grained microstructure for the sample with an undercooling of 89 K. HRTEM investigation shows a mixture of a disordered solid solution and the ordered Ni 3 Ga compound in the atomic-scale microstructure of each sample in agreement with X-ray and neutron diffraction analyses. Microhardness tests show that disorder trapping reduces the mechanical strength of the samples in spite of grain refinement. It is concluded that disorder trapping promotes plastic deformation of the Ni 3 Ga compound and that grain refinement is induced by recrystallization after rapid solidification processing. [Display omitted] [ABSTRACT FROM AUTHOR]

The non-equilibrium solidification of undercooled Inconel 718 melts has been studied in situ on electromagnetically levitated samples by using high-speed video recording and optical pyrometry. Microstructure and phase constitution of solidified samples were analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron backscatter diffraction and high-energy X-ray diffraction. Due to containerless sample processing experimental data on phase formation, γ-dendrite growth, and microstructural evolution in Inconel 718 were obtained over a wide range of undercooling Δ T between 20 and 289 K. It has been found that the dendrite growth velocity, extracted from high-speed video records, rises exponentially with increasing undercooling at first. At an undercooling of about 150 K, growth slows down drastically. Furthermore, morphology and size of γ-matrix grains essentially depend on Δ T. They alter from coarse equiaxed to coarse columnar at an undercooling of about 60 K, get refined and equiaxed at undercoolings above 150 K, and become larger and elongated again upon reaching an undercooling of about 250 K. The deviation from equilibrium and trapping of solute atoms in γ-dendrites result in a notable reduction of NbC and Laves fraction, the latter apparently disappearing at Δ T larger than 150 K. [Display omitted] • Inconel 718 melts were solidified in an undercooled state at Δ T between 20 and 289 K. • Growth velocity was determined by using high speed video and optical pyrometry. • Growth velocity rises exponentially and slows down at an undercooling of about 150 K. • Coarse grains get refined at Δ T ≈ 150 K and become larger again at Δ T ≈ 250 K. • Solute trapping at high undercooling results in reduction of NbC and Laves fraction. [ABSTRACT FROM AUTHOR]

Metastable solidification mechanisms and micromechanical property modulations of rapidly crystallizing peritectic Si 66.7 Ni 33.3 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, NiSi 2 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 NiSi 2 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 NiSi 2 to the anomalous eutectic, and the sudden drop of the sample microhardness. The solute Ni content in NiSi 2 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 NiSi 2 phase plus eutectic (NiSi + NiSi 2) 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 NiSi 2 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. [Display omitted] • Metastable solidification kinetics of undercooled Si 66.7 Ni 33.3 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 Si 66.7 Ni 33.3 peritectic alloy are experimentally measured. • Rapid solidification mechanisms of Si 66.7 Ni 33.3 alloy droplets placed on a chilling surface are studied. [ABSTRACT FROM AUTHOR]

Sector-zoned clinopyroxene records kinetic effects imposed by variable degrees of magma undercooling, ΔT , and can be utilised to track the dynamics of magmatic systems. The partitioning of trace elements into sectors grown in different crystallographic orientations can be used as a proxy for ΔT. However, an experimental assessment of the relationship between trace element zoning and ΔT has been lacking to date. Here we present trace element data from a series of undercooling crystallisation experiments on a primitive trachybasalt from Mt. Etna (Italy), at conditions of crustal storage (400 MPa, NNO + 2), and ΔT ranging from 23 to 173 °C. Changes in ΔT were modulated by varying both resting and liquidus temperatures, the latter via the melt-H 2 O content of the experiments. The resting temperature was retained for 24 h to ensure the attainment of near-equilibrium conditions. High-resolution elemental mapping reveals the distribution of trace elements in individual clinopyroxene zones. Increasing ΔT drives a shift from polyhedral morphologies with Al-rich prism and Al-poor hourglass sectors (ΔT = 23–25 °C), to skeletal (ΔT = 75–123 °C) and dendritic (ΔT = 132–173 °C) crystals with Al-rich skeletons and Al-poor overgrowths. Aluminium-rich zones have higher concentrations of rare earth elements (REE) and high field strength elements (HFSE) than Al-poor zones across all investigated ΔT conditions, and overall, Al, REE and HFSE contents increase with ΔT. This indicates that tetrahedral aluminium (TAl) and associated charge-balancing mechanisms govern the incorporation of REE and HFSE within clinopyroxene. Lattice strain parameters for REE in the M2 site indicate the incorporation of light relative to heavy REE in clinopyroxene is controlled by competing effects between the strain-free partition coefficient, D 0 , and the optimum cation radius, r 0. Critically, the middle and heavy REE switch from incompatible to compatible with increasing ΔT. Used to model fractional crystallisation, our data demonstrate that fractionation of clinopyroxene at low ΔT controls pre-eruptive melt evolution. Importantly, this indicates crystallisation of clinopyroxene in the deep portions of Mt. Etna's plumbing system is not rapid and is unlikely to result in the early formation of dendrites. We develop a parameterisation of ΔT based on REE partitioning between experimental clinopyroxene and coexisting melt, which can be applied to sector-zoned augite crystallising from mafic alkaline magmas, to reconstruct dynamic processes and thermal pathways during magma transport and storage. Applied to sector-zoned clinopyroxene microphenocrysts and groundmass microcrysts from the 1974 eccentric eruption at Mt. Etna, our parameterisation tracks an increase in ΔT with magma ascent and eruption, following recharge of Cr-rich mafic magma at depth. Sector-zoned clinopyroxene can track ΔT variations leading to volcanism at Mt. Etna and could be applied to quantify magma dynamics in other active volcanoes. [ABSTRACT FROM AUTHOR]

High-strength aluminium alloy powders modified with different nanoparticles by ball milling (7075/TiC, 2024/CaB6, 6061/YSZ) have been investigated in-situ during rapid solidification by differential fast scanning calorimetry (DFSC). Solidification undercooling has been evaluated and was found to decrease with an increasing number of nanoparticles, as the particles act as nuclei for solidification. Lower solidification undercooling of individual powder particles correlates with less hot cracking and smaller grains in the material produced by powder bed fusion of metals by a laser beam (PBF-LB/M). Quantitatively, solidification undercooling less than about 10–15 K correlates with almost crack-free PBF-LB/M components and grain sizes less than about 3 µm. This correlation shall be used for future purposeful powder material design on small quantities before performing extensive PBF-LB/M studies. [ABSTRACT FROM AUTHOR]

This article proposes an analytical model to understand the rod growth of eutectic in the bulk undercooled melt. Based on the previous derivations of the lamellar eutectic growth models, relaxing the assumptions of small Péclet numbers, the model is derived by considering melt kinetic and thermal undercoolings. The intent of this model is to predict the transitions in eutectic pattern for conditions of the low and high growth velocities. In addition to investigation of the transition between lamellar and rod eutectic patterns, mathematical simplifications of solving Bessel function are presented as well, which is the most important priority to model calculation. [ABSTRACT FROM AUTHOR]

The liquid phase separation behavior and the evolution of the solidification microstructure of a binary Cu50Fe50 alloy were investigated under the conditions of without and with a 10 T magnetic field, with different undercooling during the solidification process. Results show that the combined effect of Stokes motion and Marangoni convection leads to the formation of the core-shell structure under the condition without the magnetic field. In addition, specific gravity segregation is reinforced by increasing the undercooling, resulting in Fe-rich phase drifts towards the sample edge. In the 10 T magnetic field, the Fe-rich phase is elongated in the parallel direction of the magnetic field under the action of demagnetization energy due to the difference of static magnetic energy and surface energy. In the vertical direction, through the action of Lorentz force, the convection in the melt is inhibited and Fe-rich phase becomes more dispersed. Meanwhile, the diffusion of the two phases and the coagulation of the Fe-rich phases are also restrained under the magnetic field, therefore, the phase volume fraction of the Fe-rich phase decreases at the same undercooling in the 10 T magnetic field. The magnetic field inhibits the segregation behavior in the vertical direction of the magnetic field, and at the same time, improves the gravitational segregation to a certain extent, which has a very important impact on microstructure regulation. [ABSTRACT FROM AUTHOR]

The study of microstructural evolution in ternary Sn–Bi–Ag solder alloys is critical due to its direct impact on the mechanical properties of these low-temperature solder materials. This research compares the solidification and deformation behaviors of two such alloys, Sn–10Bi–1Ag and Sn–57Bi–1Ag, to shed light on the influences of bismuth (Bi) content variations. Experimental results indicate that increasing Bi content alters the solidification process and the degree of undercooling. In the Sn–10Bi–1Ag alloy, the eutectic reaction produces plate-like Ag 3 Sn with a predominant with { 10 1 ‾ 0 } hcp facet, considering Ag 3 Sn as a pseudo-hexagonal structure. Conversely, in the Sn–57Bi–1Ag alloy, Ag 3 Sn nucleates as the primary phase, exhibiting blocky or extensively branched morphologies, enclosed by various facets including {0001} hcp and { 10 1 ‾ 0 } hcp. Additionally, two distinct Bi particle sizes were identified in the Sn–10Bi–1Ag alloy: eutectic lamellar Bi (∼200 nm) and Bi precipitates (∼15 nm), when cooled at 10 °C/min, in comparison to typical lamellar β-Sn/Bi eutectics in Sn–57Bi–1Ag. In-situ tensile test revealed that the Sn–10Bi–1Ag demonstrates superior strength and reduced ductility. This is attributed to the reinforcement provided by the smaller-sized Bi particles and the eutectic Ag 3 Sn structures. In contrast, for the Sn–57Bi–1Ag, the primary Ag 3 Sn phase tends to fracture during deformation, and the deformation mechanism is predominantly controlled by grain boundary and phase boundary sliding. This study elucidates the significance of Bi precipitates and Ag 3 Sn in Sn–Bi–Ag solder, providing valuable insights for the alloy design of future low-temperature solders. [ABSTRACT FROM AUTHOR]

The Dakalasu No.1 pegmatitic rare-element deposit is a representative of Be-Nb-Ta pegmatites in Altai, Xinjiang, China. Beryl is the most important beryllium-carrying mineral in Dakalasu No.1 pegmatite. To constrain the concentration mechanism of Be, we conducted a study of the textural relationships and chemical compositions (major and trace elements) of beryl, along with microthermometry and Raman spectroscopy on beryl-hosted fluid inclusions. Two generations of beryl were recognized. The early beryl I was formed in the magmatic stage, whereas the late beryl IIa and IIb were formed in the magmatic-hydrothermal stage. Lithium and Cs contents increased from beryl I, beryl IIa, to beryl IIb, whereas Mg and Rb contents decreased. Scandium, V, and Ga contents of beryl IIa are similar to beryl IIb, but different in beryl I. Titanium is enriched in beryl IIa. The high FeO contents and Na/Cs ratios of beryl (I, IIa, and IIb) reveal the low degree of differentiation evolution of the Dakalasu No.1 pegmatite. Two types of melt inclusions and four types of fluid inclusions were identified in beryl IIa, IIb, and associated quartz. The microthermometry results indicated that beryl II is formed at 500 °C–700 °C, and 200 MPa–300 MPa. The Dakalasu No.1 pegmatite melt is enriched in volatiles, such as B, F, and CO2, evidenced by a large amount of tourmaline in the wall zone, the occurrence of a variety of tiny cryolite (Na3AlF6) inclusions, and CO2-rich fluid inclusions in beryl IIa. The enrichment mechanism of Be may be related to the crystallization of beryl at highly undercooled states of melt, and melt–melt–fluid immiscibility during the evolution and differentiation of the melt. [ABSTRACT FROM AUTHOR]

The present study was performed on A356 and A413 alloys containing (6–11) %Si. Measured amounts of high-purity La and Ce were added to the molten metal that was allowed thereafter to solidify at a slow rate (~ 0.8 °C/s). The results show that the addition of RE metals (La + Ce) up to 3 wt% leads to an increase in the freezing range through an increase in the melting point of the non-modified alloys by 12 °C, with a decrease in the Al–Si eutectic temperature, by 8 °C, respectively, at 3 wt% addition, regardless of the alloy Si content. Although 0.2% Ce is sufficient to drop the Te2 by about 6 °C, 1.5% Ce is required to raise the Tα2 by about 8–10 °C, regardless of the alloy composition. In the case of A413 alloy, eutectic undercooling was only observed in the non-modified base alloy. In the case of alloys modified with Sr, the presence of Sr neutralizes the effect of RE on the freezing range due to its reaction with RE. Addition of La up to 1.5% has no significant effect on the increase in either Tα2 or Te2 compared to that caused by the addition of the same amount of Ce. The increase in the freezing range with the addition of RE metals leads to the formation of a marked amount of shrinkage porosity, in particular in modified alloys. Due to the high affinity of Sr for oxidation, the porosity observed in Sr-modified alloys is twice as much as that in the non-modified alloys, on account of the porosity resulting from the presence of SrO films, in addition to that from shrinkage porosity resulting from the RE metal addition. The main RE-based intermetallics are: Al–RE–Ti, Al–RE–Si, Al–RE–TR–Si (TR = transition metals). In high Si-containing alloy, i.e., 413 alloy, Al–Re–Si compound was frequently observed. [ABSTRACT FROM AUTHOR]

This paper studies the solidification of hypoeutectic Al–Mg–Sc powders and spray deposited (SD) strips, generated by Impulse Atomization. The effects of Mg content in hypoeutectic Al–Mg–Sc was examined with respect to the extended solid solubility of Mg and Sc in α–Al, microstructure refinement and heat treatment. Increasing Mg content from 1.5 to 3wt% yielded a reduction in dendrite cells spacing by 30% in the atomized powders, and up to 10% in SD samples. Melt superheat appeared to yield a finer microstructure. The size of the primary structure in the SD was about five times larger than those of powder samples. However, the supersaturation of the primary phase is similar in both powders and SD samples, and their microhardness values (Hv0.1) are found to be ~45 and ~55 for the 1.5wt%Mg and 3wt%Mg alloys, respectively. Following aging, a significant increase in hardness is observed (75–85 for 1.5wt%Mg samples and ~85 for 3wt%Mg samples). Thus, the scale of the primary structure in both powders and SD did not contribute to the differences in the hardness. Apparently, supersaturation, the precipitation of intermetallics and solid solution of the remaining solute after aging, are the main contributors. The aging effect of liquid droplets falling on an SD layer is similar to a new layer of melted powder solidifying over a former layer in additive manufacturing (AM). Thus, powders and SD samples are a good model for building a microstructure-property database in these class of alloys for other processes such as AM. [ABSTRACT FROM AUTHOR]

The influences of the superheating temperature (Ts) on the nucleation undercooling (ΔT) of metallic melts were investigated by using molecular dynamics simulations based on the embedded atom model (EAM) potential function. The results agree with the intuitive expectation that extremely high heating rates followed by short equilibration time lead to a superheating and partial melting of the solid phase. The fraction of the remained crystalline clusters in the superheated phase depends on the superheating temperature Ts and the equilibration time, as long as Ts is below the maximal superheating. A subsequent fast cooling facilitates a substantial undercooling of the molten phase. The achieved undercooling ∆T below the steady‐state melting temperature Tm depends on the size and the concentration of the crystalline clusters remained in the liquid phase, and thus on the initial superheating temperature Ts. Based on the simulated results, a model was proposed for describing the relationship of ΔT and Ts, with which simulated data are well fitted and the maximal undercooling for metals can be predicted. [ABSTRACT FROM AUTHOR]

Both rare‐earth doping and microgravity solidification processing bring significant influences upon the structure formation and mechanical properties of various alloys. Herein, the microstructure and performance of 13Cr martensitic stainless steel are modulated by adding minor Ce content and microgravity solidification by means of drop tube technique. The lattice structure of constituent phase α(Fe) is deformed evidently by microgravity solidification, and the lattice parameter variation is 1.8 times of that caused by Ce addition. The microstructures of this steel processed by arc melting consist of lath‐shaped martensites and a few feather‐shaped bainites whose volume fraction increases with the Ce content. The bainite is replaced by ferrite in the rapidly solidified microstructure of 13Cr steel under microgravity condition. Although both microgravity solidification and Ce addition induce the microstructure refinement and inclusion spheroidization, the former effect plays the dominant role. The compressive properties and microhardness decrease moderately with Ce addition due to the slight increase in bainite, however, the microgravity solidification brought the hardening effect and thus the microhardness of the steel droplets increases with undercooling. [ABSTRACT FROM AUTHOR]

The distinctions of dendritic morphology and sidebranching behavior when solidified under atmosphere pressure, constant pressure which is higher than atmosphere pressure (hereinafter referred to as constant pressure) and periodic pressure were investigated using 3-D phase field method. When growing at atmosphere pressure, side branches (secondary dendritic arms) are irregular. When solidified under constant pressure with a relatively high value, side branches are much more luxuriant, with more developed high-order side branches. When applied with periodic pressure, resonant sidebranching happens, leading to many more regular side branches and the smallest secondary dendritic arm spacing (SDAS) in the three cases. The significant difference in dendritic morphology is associated with tip velocity modulated by total undercooling including pressure and temperature undercooling. In the case of constant pressure, tip velocity increases linearly with total undercooling, and it varies periodically in periodic pressure case. The different variation trend in tip velocity is the reason for the distinct dendrite growth behavior in different cases. Unlike the phenomenon in constant pressure case where the dendrite grows faster with higher pressure, the dendrite grows slower under periodic pressure with higher amplitude, resulting in less developed primary dendrite and side branches. This is influenced by tip remelting due to low undercooling or even negative undercooling. It is revealed that the accelerated velocity of tip remelting increases with the decline of undercooling. The greater the amplitude of periodic pressure, the faster the tip remelting velocity during one period. This is the reason why the average tip velocity decreases with the rise of amplitude of periodic pressure. [ABSTRACT FROM AUTHOR]

Crystallization processes of rare-element pegmatites are one of the key aspects in understanding pegmatite-hosted mineralization. Based on the undercooling model proposed in previous studies, the cooling time for rare-element pegmatites intruded into metamorphic rocks was estimated to be several days to several thousand years. The model, however, has not fully addressed the cooling and crystallization of rare-element pegmatites hosted by granites. Field observations and geochronology of two representative rare-element pegmatites hosted by granites in Dakalasu and Jing’erquan areas of Xinjiang illustrate that their emplacement models are different, and the granite wall rocks are at different temperatures during the moment of their emplacement. Dakalasu No.1 pegmatite(formed from(248.4±2.1)Ma to(228.4±0.3)Ma)is emplaced into the sheeting joints of a relatively cold host granite(formed at(261.4±2.1)Ma), and undercooling likely occurs in the marginal zone of the pegmatite. By contrast, the latest columbite U-Pb chronology shows that Jing’erquan No.1 spodumene pegmatite(formed at(250.8±1.0)Ma)is intruded in a relatively hot granite(formed at(252.9±1.9)Ma)through a fault. The cooling and crystallization of the pegmatite in Jing’erquan area is likely controlled by the temperature of the granite and the regional geothermal gradient, indicating a cooling history over 3 Ma. Therefore, the undercooling model and the closure temperature for the columbite U-Pb isotopic systematics need further investigation to solve the discrepancies between isotopic ages and the cooling time based on the modeling. [ABSTRACT FROM AUTHOR]

The lack of bandgap is a fundamental issue in graphene devices, which can be solved by fabricating reduced graphene oxide (rGO). However, its device integration is impeded by the elevated reduction temperature (>2000 K) requirements. Recently, we demonstrated a new approach for laser writing heavily-reduced GO by employing the nonequilibrium approach of nanosecond laser annealing (Gupta and Narayan, 2019) [1]. Here, we report on the electron mobility modulation in the liquid phase grown graphene oxide. The process involves melting and subsequent quenching of molten carbon, which triggers the first-order phase transformation of amorphous carbon (a-C) into rGO. Laser annealing at energy density above the 0.3 J/cm2 melting threshold results in liquid-phase rGO growth on Si/SiO 2. The rGO films exhibit 26 cm2/V-s room-temperature electron mobility and −4.7 × 1021/cc charge carrier concentration on annealing near melt threshold. The heavily-reduced GO films are formed on -O- creeping in the loosely-packed low undercooled carbon melt during ultrafast quenching. We establish that -O- injection is an implicit function of melt lifetime, and a rise in melt lifetime triggers GO film regrowth with increased mobility >210 cm2/V-s and 2.2 × 1019/cc carrier concentration on annealing at 0.6 J/cm2. Laser annealing resolves the fundamental issues of impurities and topological defects in rGO fabrication by equilibrium-based methods, facilitating increased electron mobility in laser patterned graphene-based materials. Image 1 [ABSTRACT FROM AUTHOR]

Anomalous eutectic formation in undercooled Ni–Sn alloys was investigated by in situ X-ray diffraction and ex situ remelting and annealing experiments. Dynamic recrystallization and partial remelting of primary solids followed by repeated nucleation and growth of eutectic grains in the mushy zone were revealed by time-resolved X-ray diffraction. Ex situ experiments demonstrated that partial remelting of near-equilibrium solidified alloys of eutectic or near-eutectic composition can convert regular lamellar eutectic into anomalous eutectic, whereas high-temperature annealing of splat-quenched alloys of similar composition can convert eutectic or two-phase dendrites into anomalous eutectic. It is concluded that compared to ripening in solid-states, partial remelting of eutectic or two-phase dendrites in a mushy zone provides a more realistic mechanism for anomalous eutectic formation in undercooled solidification of Ni–Sn eutectic alloys. Image, graphical abstract [ABSTRACT FROM AUTHOR]

We examine the apparent size of the core and shell as a function of cooling rate in core–shell particles of the metastable monotectic alloy Co-50 at% Cu, finding that the volume fraction of the core systematically increases with cooling rate and hence undercooling. A model for this variation is proposed. A Monte-Carlo simulation is used to correct for sectioning effects allowing the true core:shell volume ratio to be estimated. From this, and the observation of a second, spinodal, episode of liquid phase separation we are able to estimate the undercooling at solidification. This permits a calculation of the time available following liquid phase separation for the migration giving rise to the observed core–shell structure to occur and hence the required Marangoni velocity required to such migration. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Reducing the enthalpy of as-deposited amorphous films is desirable as it improves their kinetic stability and enhances the reliability of resulting devices. Here we demonstrate that Ge 15 Te 85 glass films of lower enthalpy are produced by increasing the voltage during magnetron sputter deposition. An increase of ~100 V leads to a drop in effective cooling rate of almost three orders of magnitude, thereby yielding markedly lower enthalpy glasses. The sputtering voltage therefore constitutes a novel parameter for tuning the fictive temperature of glass films, which could help to obtain ultra-stable glasses in combination with substrate temperature control. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The forming mechanism of anomalous eutectic structure (AES) in undercooled eutectic alloys has been a controversial issue. In this work, we conducted in situ observation of the AES forming process in an Ni-18.7 at.% Sn eutectic alloy using a high-temperature laser scanning confocal microscope. Our results provide an evidence of the AES formation induced by remelting of primary eutectic lamellae constituted by Ni 3 Sn and α-Ni lamellae. During recalescence, a pronounced remelting of the Ni 3 Sn phase into liquid occurs, while the α-Ni lamellae subject to a rapid morphological transition into granules. Eventually, the completion of solidification leads to the AES formation. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The non-equilibrium response of a high entropy alloy CoCuFeNiTa 0.5 has been studied using undercooling as a control parameter. The solidification growth rates are rapid (30–50 m/s) at deep undercooling (>150 °C) and are comparable with conventional alloys. The elemental segregation especially that of Cu as predicted by phase field simulations in lower (<50 °C) undercooling regime matches with the experimental observations. This study indicates that even extreme non-equilibrium conditions during solidification could not avoid elemental segregation at the atomic scale. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The first part of the paper summarizes the performance of two mould devices, illustrating by representative shrinkage tendency results in ductile cast iron as affected by mould rigidity (green and furan resin sand moulds) and inoculant type (FeSibased alloys). Less rigid green sand moulds encourage the formation of contraction defects, not only because of the high initial expansion values (εdi)max, but also because of the increased solidification undercooling. A high inoculation efficiency means not only lowering the carbides formation sensitivity and increasing the nodule count, but also a prolonged graphitization through to the end of the eutectic freezing, as observed by the high population of small late forming nodules, which leads to minimizing the tendency for shrinkage. The second part of the paper illustrates an application of this equipment to commercial foundry use. It conducts thermal analysis and volume change measurements in a single ceramic cup with cast iron quality as a variable. La-bearing FeSi inoculant appears to be more effective than RE (Rare Earth) -FeSi alloy in FeSiMgCa treated irons (no RE), in terms of reducing eutectic undercooling and (εdi)max, favourable for lower sensitivity to shrinkage formation. Experiments also compared solidification patterns for white [WI], grey [GI] and ductile [DI] irons, to correlate the most important events between the cooling curves and contraction curves, to evaluate the sensitivity to shrinkage formation. All of the irons have similar values for initial expansion up to the start of eutectic freezing, but, after that, the graphite formation promotes expansion (more than 5 times for nodular graphite), resulting in a difference in maximum expansion (2 times higher for DI). The graphitic expansion has two contrary effects. Increased graphitic expansion (force) leads to a higher shrinkage sensitivity during the first part of the eutectic reaction, but also to a decrease of shrinkage at the end of solidification, due to forcing the last liquid iron to occupy the previous formed cavities. Consequently, strong graphitization process promotion at the end of solidification favours the castings' soundness. [ABSTRACT FROM AUTHOR]

Sandwiched between two fused silica blocks, thin-gauge samples of Ag-39.9 at.%Cu eutectic alloy were solidified over a range of undercoolings. Subsequently, the samples that consisted consistently of fully lamellar eutectic were rapidly heated to a target temperature below the eutectic temperature. Increasing the initial undercooling prior to solidification or the target temperature of heating led to more anomalous eutectic and worse orientation of phases in the final microstructure. It is conclusively indicated that the formation of anomalous eutectic in bulk samples results from remelting of the primary lamellar eutectic. Unlabelled Image [ABSTRACT FROM AUTHOR]

Isothermal and undercooling experiments were conducted on one of the most primitive trachybasalts from Mt. Etna volcano in order to examine the crystallization mechanisms controlling the textural and compositional variability of clinopyroxene. Experiments were performed at 400–800 MPa, 1050–1200 °C, 0–4 wt.% H 2 O and at oxygen fugacity 2 log units above the Ni-NiO + 2 buffer. In isothermal experiments, the final resting temperature is approached from room temperature and clinopyroxene growth is dominated by an interface-controlled mechanism, leading to the formation of small (∼10 µm) and euhedral crystals with homogeneous compositions. Conversely, in undercooling experiments, the final resting temperature is approached after annealing at temperature above the liquidus , imposing an effective degree undercooling (Δ T) to the system. In presence of undercooling, the crystallization of clinopyroxene is dominated by a diffusion-controlled mechanism that determines the formation of large (>100 µm) crystals, constituted by two compositionally distinct domains, enriched in Al 2 O 3 + TiO 2 and SiO 2 + MgO, respectively. The maximum growth rate (G max) decreases progressively from ∼10−7 to ∼10−8 cm/s as the degree of undercooling increases from ∼20 to ∼230 °C, due to the increase in nucleation rate. At low to moderate degrees of undercooling (Δ T = 23–41 °C) clinopyroxene is prevalently euhedral to subhedral, whereas at high degrees of undercooling, the crystal shape changes from prevalently subhedral (Δ T = 73–123 °C) to skeletal and dendritic (Δ T = 132–233 °C). Hourglass sector zoning similar to that documented for natural phenocrysts from eruptions at Mt. Etna volcano is observed only at low degrees of undercooling (Δ T = 23–32 °C). This type of zoning develops in the form of the cation exchange [Si + Mg] {-111} ↔ [Al + Ti] {100} and demonstrates that hourglass sector zoning is an effective indicator of sluggish kinetic effects caused by relatively low degrees of undercooling. In contrast, at increasing degrees of undercooling (Δ T > 32 °C), strong melt supersaturation determines the early formation of Al 2 O 3 + TiO 2 -rich dendritic crystals and further SiO 2 + MgO-rich overgrowths, as the bulk system attempts to return to a near-equilibrium state between the advancing crystal surface and the feeding melt. The experimentally-determined relationship between Δ T and clinopyroxene chemistry is used to reconstruct the crystallization conditions of natural clinopyroxenes from 1974 and 2002–2003 eccentric eruptions at Mt. Etna volcano. Clinopyroxene rims record much higher degrees of undercooling (up to ∼110 °C) than crystal mantles associated with magma recharge at depth (mostly 0–40 °C). Hence, the rims track decompression-induced degassing and cooling during the ascent of magma towards the surface. [ABSTRACT FROM AUTHOR]

Classic kinetic theories for crystal growth and melting, such as diffusion- or collision-limited theories, encounter challenges in quantitative describing the interface velocity at large values of the driving force. One possible solution of such a crisis of classic theories is seen in using the kinetic phase field model (KPFM) formulated for small and large driving forces on solidification, melting and evaporation. The predictions of the nonisothermal phase field model are discussed in the present work to describe the nonlinear behavior of the nickel crystal growth obtained in molecular dynamic (MD) simulation. • The comparison of the phase field modeling with data of atomistic simulation is made. • The kinetic phase field model exhibits flexibility to describe data of molecular dynamics simulation. • Non-isothermal phase field model has been developed for fast crystal growth. [ABSTRACT FROM AUTHOR]

Droplet supercooling in marine icing tests is studied theoretically using established correlations for convection and evaporation. The effect of freestream turbulence on heat and mass transfer is included through an empirical modification to the Nusselt and Sherwood numbers. Droplets are shown to cool following a modified exponential decay, with the trajectory length and shape determined by a thermal mixing length and a cooling exponent. The space needed for supercooling is shown to increase with (droplet diameter)1.8, and also depend on wind speed, injection speed and ambient temperature. Turbulence at realistic offshore levels shortens cooling distances by up to 50%. A reanalysis shows that previous marine icing tests have typically reached supercooling higher than 80% of cooling potential for small droplets up to 100–200 μm, and possibly up to 300–400 μm in long setups at low wind speeds if boosted by turbulence or a contracting tunnel; larger droplets have been significantly undercooled compared to field conditions. • Droplet thermal trajectories follow exponential decays with front-loading. • Trajectories can be expressed using a thermal mixing length and a cooling exponent. • Moderate turbulence may shorten droplet cooling distances by up to 50%. • Marine icing tests have typically reached almost full supercooling for droplets up to 100–200 μm. [ABSTRACT FROM AUTHOR]

[Display omitted] • Sn heterogeneous nucleation on (Pd,Ni)Sn 4 compound greatly reduces Sn undercooling. • Sn undercooling reduction attributes to single-grain formed in micro-bump. • Single-grain restricts electromigration and consumption of electroless-Ni. • Ni 3 P formed at solder/Ni(P) interface degrades EM lifetime. The heterogeneous nucleation on the limited (Pd,Ni)Sn 4 compound observed at the solder/Pd/Ni(P) interface greatly reduces the Sn undercooling. The undercooling reduction of Sn is the key resulting a single-grain structure for the Sn-rich Sn1.5Ag0.1Cu micro-bumps. Without (Pd,Ni)Sn 4 compound formed at the solder/Pd/Ni(P) interface, the Sn-rich Sn1.5Ag0.1Cu micro-bumps has a polycrystalline grain structure. Compared to the solder matrix with poly-grains structure, the single-grain solder matrix restricts electromigration atomic flux and the consumption of the Ni(P) layer, which mitigates EM effect and prolongs EM life time of the micro-bumps. Ni 3 P layer formed at the solder/Pd/Ni(P) interface greatly influence EM behavior and lifetime. [ABSTRACT FROM AUTHOR]

Quaternary Fe-20 %Mo-12 %Ni-6 %Cr alloy with various composite magnetic structures was fabricated through electromagnetic levitation (EML) coupled with multi-mode quenching techniques. The magnetic domain distributions were characterized and related to the macro/micro-magnetic properties of this containerlessly processed alloy. Under EML condition, nano-scale lamellar (αFe) + Fe 2 Mo eutectoid structures with completely disordered magnetic domains were formed at small undercoolings. But the eutectoid morphology became anomalous and a ferromagnetic (αFe) single-phase zone with clear stripe domains appeared as undercooling increased, resulting in the obvious improvement of saturation magnetization, coercivity and residual magnetization. The (αFe) + Fe 2 Mo eutectoid structures were entirely suppressed by multiple quenching processes to secure (αFe) single-phase microstructures with ordered domain distributions including the stripe domains with grain boundary contrast, the maze domains with developed branches and their coexistent mixtures. These magnetic structures displayed much higher saturation magnetization, much lower coercivity and almost unchanged residual magnetization as compared with the highly undercooled alloy at EML state, indicating that the soft magnetic property of this alloy was significantly enhanced after rapid quenching. Moreover, the spin distributions and atomic magnetic moments of two constituent phases were analyzed by first-principle calculations, which were in good accordance with the experimental results. [Display omitted] • Electromagnetic levitation coupled with quenching techniques were adopted to fabricate various magnetic structures. • The morphology and proportion of eutectoid structure could be modulated by increasing the undercooling or cooling rate. • The macro-magnetic properties of alloy were related to the domain structure ordering. • The origin of alloy magnetism was revealed by calculating the spin and magnetic moment on atomic scale. [ABSTRACT FROM AUTHOR]

Molecular dynamics simulation was applied to investigating the evolvement rule of cobalt melt microstructure during solidification at different cooling rates. The cooling rate for the formation of amorphous phase is determined by analyzing the radial distribution function, the H–A bond-type index and the mean square displacement. The simulation results showed that the nucleation undercooling increases with the initial temperature, and in the undercooling versus temperature curve, there are two inflection points. Besides, when the initial temperature reaches 2450 K, the undercooling will be stabilized at 1061 K. As the cooling rate is less than 1.0 × 1011.0 K s−1, the FCC and HCP crystal structures will be obtained. Amorphous structure will be obtained if the cooling rate is more than 1.0 × 1013.0 K s−1. If the cooling rate of the Co melt is between 1.0 × 1011.0 and 1.0 × 1013.0 K s−1, the crystal and amorphous structures will be coexistent, which indicates that the critical cooling rate of crystal–amorphous transition is 1.0 × 1011.0 K s−1. [ABSTRACT FROM AUTHOR]

The increasing demand for pre-pouring melt quality evaluation by thermal analysis has led to some important breakthroughs in understanding the solidification of spheroidal graphite cast iron (SGI). The two important parameters which characterize the solidification cooling curve of SGI are temperature of eutectic undercooling (TEU) temperature of eutectic recalescence (TER). In this study, the response of preconditioning treatment (0.1% Al,Zr,Ca–FeSi) on TEU and TER was investigated in several samples from different heats. It was found that preconditioning increases both TEU and TER. The average eutectic graphitization ability after preconditioning was found to increase from 60 to 75. The average undercooling (∆T) and recalescence (∆Tr) in preconditioned samples were 12 °C and 2 °C, whereas in samples without preconditioning average ∆T and ∆Tr are 19 °C and 7 °C, respectively. Preconditioning improves graphitization ability thereby increasing the graphite nodule count. The actual nodule count of SG iron samples obtained by image analysis was found to be in agreement with that of nodule counts predicted by thermal analysis. [ABSTRACT FROM AUTHOR]

We report direct conversion of multiwall carbon nanotubes (CNTs), synthesized by chemical vapor deposition, into diamond by nanosecond pulsed laser melting process at ambient temperature and pressure in air without any catalysts. The Raman spectroscopy of the CNTs after the laser irradiation showed the characteristic diamond peak at around 1324-1325 cm−1. The downshift of this peak from its theoretical position (at 1332 cm−1) is explained by phonon confinement in nanostructured diamond. The SEM and TEM images show the formation of diamond mostly at the tip and bends of the CNTs. The grain size distribution and the shape of the converted nanodiamonds suggest that the transformation takes place by melting of the CNTs in a super undercooled state by nanosecond laser pulses, and subsequent rapid quenching to convert it into phase-pure diamond. The EBSD analysis illustrates the phase-pure single crystal diamond formation at the tips and bends of the CNTs. The high-resolution electron energy-loss spectrum in the STEM contains characteristic σ* peak at 292 eV for sp3 bonding of diamond. This study on the laser-induced direct conversion of CNTs to diamond marks a major breakthrough in the formation of diamond nanostructures and diamond-CNT hybrid for a variety of potential applications. Image 105119 [ABSTRACT FROM AUTHOR]

Solidification and growth behavior of undercooled eutectic CoSi–CoSi 2 melts was observed using containerless levitation and in situ high-energy synchrotron X-ray diffraction techniques. Three metastable solidification pathways of eutectic CoSi–CoSi 2 were determined as a function of undercooling. Upon double recalescence at low undercoolings the primary and secondary phases are CoSi and CoSi 2 , while at high undercoolings the phase formation sequence is reversed. At intermediate undercoolings a single recalescence was observed and attributed to a crossover of the nucleation barriers for the two phases. Scanning electron microscopy combined with electron back-scattering diffraction measurements revealed changes of the morphological characteristics and orientation of CoSi and CoSi 2 phases for different solidification pathways. Image 1 [ABSTRACT FROM AUTHOR]

Al solidification on Al2O3 single-crystal substrates with (0001) and (11 2 ¯ 0) termination surfaces was performed to investigate whether the lattice mismatch can influence the heterogeneous nucleation when the same kind of substrate was employed. Nucleation undercooling was measured via differential scanning calorimeter to present the nucleation potency of Al on selected substrates. The measured results show that the lower undercooling was achieved in Al/Al2O3(11 2 ¯ 0), which means that the Al has a higher nucleation potency on Al2O3(11 2 ¯ 0) substrates. This is consistent with the calculated lattice misfit of Al/Al2O3(0001) and Al/Al2O3(11 2 ¯ 0) based on Bramfitt two-dimensional model because the lowest lattice misfit of Al/Al2O3(11 2 ¯ 0) is less than that of Al/Al2O3(0001). Moreover, the corresponding orientation relationships at the interface achieved by high-resolution transmission electron microscopy are almost the same with the predicted one from lattice misfit calculation. It is proved that the lattice misfit does affect the heterogeneous nucleation even the melted metals nucleated on the substrates made of the same kind of material. [ABSTRACT FROM AUTHOR]

A novel banded microstructure consisting of regular/anomalous eutectic has been found in hypoeutectic Co-61.8at%Si rapidly solidified by either copper mould casting and melt spinning. The bands originate because of varied undercooling and growth rate in the direction of heat flow towards the copper sinks. Diffusional effects (i. e. rejection of solute) in the presence of limited convection cause fluctuations in growth rates for which the role of recalescence is highlighted. Occasional primary phase/eutectic transitions were also found. The microstructures are contrasted with those seen in furnace cooled samples where diffusion fully occurred in a quiescent melt. Unlabelled Image [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The larger undercooling results in an increase in the size of the Co-rich phase. • The Co-rich phase in the direction of the vertical magnetic field becomes dispersed. • A rod-like shape with Co-rich phase parallel to the direction of the magnetic field. • The volume fraction of Co-rich phases decreases remarkably under high magnetic field. Abstract The effects of high magnetic field on the microstructure evolution of non-equilibrium solidified Cu 80 Co 20 alloy have been investigated by glass fluxing combined with cyclic superheating and cooling method in a superconducting magnet. Results show that both the undercooling and magnetic field can affect the microstructure of Cu 80 Co 20 alloy. The size of Co-rich phase increases with the enlarged undercooling. The Co-rich particles are elongated along the direction of 6 T magnetic field while these granules become more dispersed perpendicular to the direction of 6 T magnetic field. Moreover, the volume fraction of Co-rich phases perpendicular to the 6 T magnetic field reduces significantly. [ABSTRACT FROM AUTHOR]