Chill Zone Research Articles

Molten pool free surface solidification behavior in laser remelted near-β titanium alloy

Free surface solidification (FSS) is a common physical phenomenon that has been found by various studies in metallurgy field while targeted studies are rare. This work investigated special structure and formation mechanism of surface grains generated by free surface solidification through laser remelting a near-β titanium alloy Ti-5Al-5Mo-5V-1Cr-1Fe (Ti-55,511). A thin layer crystal film covers molten pool surface through two-dimensional constrained solidification, which can be classified into flake-like crystal film located at molten pool edge and lotusleaf-like crystal film at molten pool center. Numerous cells grow from overflowing melt chill zone around molten pool edge and undergo two-dimensional constrained growth on surface, forming flake-like crystal films. TiNx particles formed from surface melt and N2 reaction can act as heterogeneous crystal nuclei, forming lotusleaf-like crystal films, whose secondary dendrite arm growth direction transforms from 〈100〉 of primary dendrite arm to 〈110〉. Equiaxed lotusleaf-like crystal films and columnar flake-like crystal films have a competitive growth relationship. Inward growth cells growing from two kinds crystal films form flake-like surface grains and central surface grains, respectively. This study can provide FSS theoretical guidance for laser additive manufacturing and surface modification.

Architectural and Compositional Diversity of Early Earth Ocean Floor Evidenced by the Paleoarchean Nondweni Greenstone Belt, South Africa

Abstract The nature of the early Archean ocean floor remains a topic of important debate. There are relatively few well-preserved occurrences worldwide where such terrains may be studied in detail because of structural dismemberment, metamorphic overprinting and pervasive early stage hydrothermal alteration to recent weathering. The 3.41-Ga dominantly mafic formations of the Nondweni Greenstone Belt (NGB) covering 270 km2 in the south-eastern Kaapvaal Craton comprise submarine volcanics that exhibit a wide range of textural features, including pillows, chill zones and brecciated flow tops, and various spinifex textures, including the rare platy pyroxene type, cumulate layers, and tuffs. Channelized subaqueous lava lakes that underwent fractionation are capped by thick spinifex-textured units and pillows. Early stage seafloor alteration is regionally variable, ranging from intense to minimal, with preservation of original mineralogy in many areas. Mafic volcanic rocks of the NGB contrast with those of the Barberton Greenstone Belt both in the style of volcanism and in the associated compositional range of komatiitic basalt to basalt with a complete absence of high-Mg komatiites. Olivine-phyric rocks, or derivatives thereof, are largely absent and pyroxene is the main controlling phase with orthopyroxene in the most primitive komatiitic basalts and clinopyroxene in the evolved lava lake sequences. The abundance of orthopyroxene typifies the long-standing silica-enriched character of the Kaapvaal Craton. Three exceptionally well-preserved and well-exposed sequences were studied utilizing hand-drilled samples and deep coring providing unprecedented stratigraphic and textural detail and field controls for more than 400 samples. A unifying feature of the mafic volcanics of the NGB is the range of compositions and ratios of incompatible elements most clearly illustrated by a series of high- and low-Ti compositional lineages reflecting differing sources or degrees of mantle partial melting. Sharp boundaries between high- and low-Ti flow successions indicate sudden changes in the melting regimes or the interaction of flow sequences from different volcanic centres. Th/Nb ranges from 0.1 to 0.2 and reveals crustal contamination of primitive lavas. The primary magma that gave rise to the most primitive komatiitic basalts with 19.5% MgO was derived from partial melting of a mantle plume source in the garnet stability field. Trace element modeling shows that the sequences studied in detail have been modified by fractionation and crustal contamination with the most likely contaminant being the Ancient Gneiss Complex (3.43–3.66 Ga), which is extensively exposed in Eswatini and probably underlies the Paleoarchean terrains in the southern Kaapvaal Craton. The geotectonic setting was likely that of a submerged felsic crustal platform as enclaves within an oceanic plateau.

Influence of cast iron vacuuming on the level of mechanical characteristics of the material of the working layer of double-layer chromium-nickel rolls

The object of research is chromium-nickel cast iron of the working layer of two-layer sheet-rolling rolls of the LPKhNd design. At present, chromium-nickel cast iron is widely used for the manufacture of rolls for sheet and section rolling mills. One of the ways to improve the operational properties of products made of chromium-nickel cast iron is the refining of molten metal by vacuum. The existing problem is that information on the effect of vacuuming on the performance of chromium-nickel iron is very limited. Rolls with the most characteristic concentration of alloying elements for LPKhNd performance were selected for the study. When evaluating the properties of vacuumed cast iron and cast iron by traditional technology, the level of strength, hardness, as well as special properties were determined, the study of which is caused by the peculiarities of the operation of rolling rolls (thermal wear resistance and crack resistance). It has been established that there is no significant difference in the structures of rolls made of vacuumed and non-vacuumed cast iron. The structure of the rolls consists of martensite, bainite and carbides. With an increase in the content of graphite-forming elements (C, Si, Ni), graphite inclusions appear in the structure, and with their decrease, individual troostite colonies appear. The physical and mechanical properties of vacuumed and non-vacuumed cast iron are on the same level. The crack resistance of the chilled zone of vacuum cast iron is 12.35 % higher than that of cast iron of the traditional production method, and the transition zone is 11.96 %. The thermal endurance of the chilled zone of the roll material increased by 14.95 % as a result of vacuuming of the molten metal, and the transition zone – by 14.56 %. An increase in crack resistance and heat resistance can help reduce the chipping of the working layer of chromium-nickel rolls of sheet mills during operation and increase their resource indicators. The obtained results of research indicate a positive effect of vacuuming on individual indicators (crack resistance and heat resistance) of the working layer of the forming tools of sheet rolling mills.

Petrogenetic implications of Fe–Mg substitution in clinopyroxene lattices of basaltic suites of Khandwa area, eastern Deccan volcanic province, Central India

Field investigations and lava flow mapping around Khandwa (21°49′ N:76°21′ E), Central India (within the eastern Deccan volcanic province) record three distinct lava flows which are in general, characterized by several structural zones, for example, Lower Vesicular Zone, Lower Colonnade Zone, Entablature Zone (EZ), Upper Colonnade Zone (UCZ), and Upper Vesicular Zone (UVZ). Different lava flows (often with chilled zones) in the field have been marked by discontinuous thin intertrappean beds. The occasional presence of chilled dyke and feeder dyke (both associated with Flow II) has also been noticed. The entire lava succession rests over coarse‐grained (cumulate) gabbroic (apparent) basement. Deduced clinopyroxene ordering clearly indicates that 100% initial ordering had been achieved for Flow II chilled zone, Flow II UCZ, Flow III UCZ, Flow III EZ, and cumulate gabbro. On the contrary, Flow II UCZ (97.35% initial ordering), feeder dyke (98.76% initial ordering), chilled dyke (99.82% initial ordering), and Flow I chilled zone (99.07% initial ordering) show initial clinopyroxene disordering (<100% ordering), which were later subjected to a gradual process to achieve ordering. Second‐order regression analyses clearly indicate that the progressive clinopyroxene ordering‐process is controlled by several differentiation parameters namely An% of coexisting plagioclase, lower thermometric values, and FeOt/MgO. In addition, roles of AlVI, Ti4+, and Fe3 were also suggested to influence the clinopyroxene ordering‐style. Based on Ti/6ox versus Al/6ox relation of clinopyroxene, it was deduced that cooling rate appreciably controls the clinopyroxene ordering‐behaviour. We contemplate that variation in clinopyroxene ordering‐pattern in basaltic rocks of Khandwa represents interplay of differentiation parameters and cooling rate of the ambient magma.

Determining Alloy Nucleation Core Origin and Grain Refinement Strategy Based on the Dependence Degree of Content Difference

What is nucleation core origin during alloy solidification, especially for equiaxed grains? Different dependence degrees of the magnitude or occurrence of element content variation could shed light on this long-standing issue in actual large ingots. Here, based on etched surface height and grayscale, element content distributions within the solid fraction in continuous casting billets and additive manufacturing samples are first obtained by only a two-dimensional surface. Then, combined with the phylogenetic trees, the rank correlation is applied to measure the dependence of content differences during initial solidification. Assessments of external dependence degrees are helpful to determine nucleation core origin and low internal dependence degree facilitates grain refinement. Moreover, in continuous casting, some nucleation cores in the central equiaxed grain zone are confirmed to originate from the edge-chilled zone and high equiaxed grain area ratio under a low superheat, which is attributed to the low ratio of temperature gradient to growth rate rather than remelting fewer cores originating from the chilled zone. In addition, the floating behavior of separated grains originating from the chilled zone can be affected by gravity force, but these grains should be more active when increasing the casting superheat that may weaken the influence of gravity to a certain extent.

The mechanism of columnar-to-equiaxed transition during electromagnetic centrifugal solidification

Abstract A series of Hastelloy C tubes were solidified under a centrifugal field with various conditions of bulk liquid flow obtained with a controllable electromagnetic field. Their macrostructures show that the columnar-to-equiaxed transition was promoted both by increasing electromagnetic stirring and by increasing the superheat, and the application of electromagnetic stirring at different times can also influence the percentage of the total area occupied by the equiaxed region. Mechanical damage of dendrites is the most probable mechanism for the promotion of the columnar-to-equiaxed transition with high velocity flows. The detachment of the nuclei originated in the chill zone can also promote the columnar-to-equiaxed transition.

Study of impurities in newly manufacturing 1215MS+Bi steels by altering cooling processes

ABSTRACT To accurately study the distribution characteristics of impurities and microstructures in the 2800 ppm Bi content 1215 MS steel, the horizontal solidification experiments were carried out by altering horizontal cooling processes. Results show that under moving rates (υ) = 0.3 mm/s and 0.5 mm/s the equivalent diameters of the impurities in steels at the interface between the chilled grain zone and columnar grain zone were higher at 1.6 ~ 1.8 μm, 2 ~ 3 times larger than those in the chilled boundary. Most small-sized inclusions were gathered in circular or linear distribution with the sizes of <1.0 μm. The morphologies of MnS/Bi-MnS inclusions were in rod-like, long strip, spindle, ellipsoidal, and spherical shape. The high υ value was beneficial for increasing the equivalent diameters of the impurities in the chilled grain zone and resulted in the reduction in the inclusions sizes in the columnar grain zone but it seldomly affected their sizes in the equiaxed grain zone. The morphologies of the equiaxed grains were in directional stacking, cross, anisotropy and coniferous pine types.

Chilling Effect of Inoculation on the Microstructure and Hardness Property of Hypo-Eutectic Grey Cast Iron

The influence of varied weight percent of inoculant (ferrosilicon) on the microstructure and hardness property of hypo- eutectic grey cast iron was investigated. Four sets of chill wedge samples were produced using two chill wedge wooden patterns (W3 1/2 and W4). The first set, the control samples W3 1/2 and W4 were uninoculated. The second, third and fourth sets were inoculated with 1.0wt.%, 1.5wt.% and 2wt.% ferrosilicon respectively to give inoculated samples W3 1/2 and W4. Wedge test was conducted on the samples at the four different points (1, 2, 3 and 4) in accordance with ASTM A367. From the results, microstructures of the control and the inoculated samples were differently influenced by the varied percentage of the inoculant at the four designated points 1, 2, 3 and 4. The average hardness property of the inoculated samples decreases with increasing ferrosilicon addition. Samples W3 1/2 and W4 with 1.0wt.% ferrosilicon revealed high hardness property at chill zone, and hardness property of W3 1/2 was high relative to sample W4 with the values of 34.9 HRA and 30.6 HRA respectively. Similarly, the control samples showed the highest hardness property at the chill zone. Sample W3 1/2 revealed high hardness value of 33.0 HRA relative to sample W4 of 26.8 HRA at the chill zone. Keywords - inoculant; Microstructure; hypo- eutectic; chill zone; hardness property

Experimental investigation of Te addition on chilled cast iron tappet manufacturing process

ABSTRACT The chilled cast iron tappet comprises three gradient microstructures, including chill, mottle, and gray iron. In this work, the effect of Tellurium (Te) on the chilled iron tappet’s microstructure and properties is studied. The addition of Te to gray cast alloy enhances its mechanical and thermal properties, which can be used in new designing of materials for heavy automotive applications. The gray cast iron alloy with 0.01 to 0.05 wt.% of Te was prepared in order to examine the effect of Te wt.% on the chill depth, microstructure, wear, and hardness. The scanning electron micrographs are used to distinguish and analyze the chill zone, mottle, and gray zone in the tappet, and the hardness was studied by Vickers hardness test, and wear behavior by a pin on disc method was measured. The present study showed that the addition of Te strongly influenced the formation of chill and efficiently enhanced the tappet’s mechanical properties along with the favorable effect to eliminate the mottled zone and separate the chill zone and gray zone with a clear boundary.

An Empirical Model for Carbon Diffusion in Grey Iron/Stainless Steel Bimetallic Composites Incorporating Eutectic Carbides

The mechanism of carbon diffusion in the as-cast and heat-treated grey iron and 304 stainless steel bimetallic composites was investigated in this study. A simplistic empirical model for the interface carbon diffusion was proposed and has been validated against the experimental data. A liquid-solid compound casting technique was used to fabricate the bimetallic composites. For the graphitizing annealing heat treatment, the bimetallic composite specimens were heated to 940 °C and held for 120 min and 240 min in an electric heating furnace. The proposed empirical model is based on the presence of eutectic carbides chill zone near the interface that formed during solidification of the liquid grey iron above the solid stainless steel substrate. It was found that the calculated carbon concentration profiles based on the proposed diffusion model were in good agreement with the experimental results.

Windowing petrogenesis of continental flood basalts through mineralogical investigations: a case study from the Eastern Deccan Volcanic Province

Evaluation of the petrogenetic history of continental flood basalt using mineral–chemical data has been sparingly used for several flood basalt provinces of the world. For the Deccan flood basalts, such attempts are still rudimentary. The present contribution highlights several facets of petrogenesis of the Eastern Deccan Volcanic Province using details of constituent phases including glass. The present-study area around Khandwa (21°49′N, 76°21′E) indicates the presence of three distinct lava flows, which were identified on the basis of physical volcanological features based on a three-tier classification. Moreover, the occasional presence of chilled dykes and feeder dykes has been documented. The lava succession rests above (apparent) cumulate gabbro basement. The lava flows, in general, are characterized by dominant pyroxene (mostly augite, locally pigeonite) and plagioclase, opaque (magnetite and ilmenite) and glass, whereas olivine is rare. Both of these principal mineral phases (namely, plagioclase and pyroxene) occur both as phenocrysts and groundmass, while opaque phases occur only as groundmass. Pyroxene and plagioclase are generally zoned due to the changing milieu of crystallization conditions. Pyroxene thermometry data show the equilibration temperature range of 1050–1300 °C. Except for two samples of Flow II and one sample of chilled zone, the pyroxene thermometry data are broadly similar to that obtained from magnetite–ilmenite thermometry. As expected, deduced glass thermometric data reveal a relatively higher temperature. Crystallization history of parental magma was quantitatively modeled using Petrolog 3 software. The results indicate that the parental magma underwent both equilibrium and fractional crystallization (for example initially crystallized olivine reacted with ambient liquid to give rise to pyroxene). Phenocrystal and groundmass plagioclase and pyroxene show distinct patterns of compositional zoning corresponding to fluctuating physical parameters within the magma. Some of the glass [especially from the chilled dyke, feeder dyke, and Upper Colonnade Zone (UCZ) of flow II and flow III] represents ‘higher magnitude pressure ambience’ (fossilized glass) which is distinct from ‘surficial glass’ caused by equilibrium quenching. The glass and pyroxene compositions (using tectonic discrimination diagrams) suggest a non-orogenic continental setting of the parent magma. It is concluded that the studied Deccan volcanism shows a complex interplay of repeated pulses of magma ascent, fluctuation of crystallization condition, effervescence, and local magma mixing.

ТЕОРЕТИЧЕСКОЕ ОБОСНОВАНИЕ УГЛОВОЙ КОРРЕКЦИИ ВЕКТОРА ПОТОКА СТРУИ ПРИТОЧНОГО ВОЗДУХА В СИСТЕМАХ ВЕНТИЛЯЦИИ ПРОМЫШЛЕННЫХ И СЕЛЬСКОХОЗЯЙСТВЕННЫХ ОБЪЕКТОВ

During the heating period, the supply air temperature is lower than that in industrial premises, and the cooled air is denser. Entering a warm room, it tends to move downward. This condition leads to the formation of chilled and stagnant zones. The article presents a theoretical study on the possibility of ensuring the maximum propagation range of a non-isothermal supply air jet by angular correction of the fl ow vector at the outlet of the ventilation unit. Based on the theory of free air distribution, the author analyzed and graphically visualized the fl ow trajectories of the supply air from the combined climate control unit with heat recovery in the production room in the range of outdoor temperatures from +10 to –40°C. Given the time period of outdoor temperatures, fl at sections of a three-dimensional graph were built with a step of 10°C in the range from +10 to –30°C. The author found that the maximum service area of the installation is limited by the propagation range of the supply air jet. The area can be increased by changing the direction of the fl ow vector by an angle ranging between 0 and 34°. The value of the inclination angle of the fl ow vector of the supply air jet is determined by the obtained approximation dependency. Considering the regulation of the fl ow vector, the author used the formula of M.Z. Pechatnikov to determine the propagation range of a limited axisymmetric jet. The studies carried out made it possible to establish the relationship between the propagation range of the supply air jet of the installation and the outside temperature, the inclination angle of the fl ow vector, and the theoretical variation range of the inclination angle of the fl ow vector, ranging between 0 and 34°.

ТЕОРЕТИЧЕСКОЕ ОБОСНОВАНИЕ УГЛОВОЙ КОРРЕКЦИИ ВЕКТОРА ПОТОКА СТРУИ ПРИТОЧНОГО ВОЗДУХА В СИСТЕМАХ ВЕНТИЛЯЦИИ ПРОМЫШЛЕННЫХ И СЕЛЬСКОХОЗЯЙСТВЕННЫХ ОБЪЕКТОВ

During the heating period, the supply air temperature is lower than that in industrial premises, and the cooled air is denser. Entering a warm room, it tends to move downward. This condition leads to the formation of chilled and stagnant zones. The article presents a theoretical study on the possibility of ensuring the maximum propagation range of a non-isothermal supply air jet by angular correction of the fl ow vector at the outlet of the ventilation unit. Based on the theory of free air distribution, the author analyzed and graphically visualized the fl ow trajectories of the supply air from the combined climate control unit with heat recovery in the production room in the range of outdoor temperatures from +10 to –40°C. Given the time period of outdoor temperatures, fl at sections of a three-dimensional graph were built with a step of 10°C in the range from +10 to –30°C. The author found that the maximum service area of the installation is limited by the propagation range of the supply air jet. The area can be increased by changing the direction of the fl ow vector by an angle ranging between 0 and 34°. The value of the inclination angle of the fl ow vector of the supply air jet is determined by the obtained approximation dependency. Considering the regulation of the fl ow vector, the author used the formula of M.Z. Pechatnikov to determine the propagation range of a limited axisymmetric jet. The studies carried out made it possible to establish the relationship between the propagation range of the supply air jet of the installation and the outside temperature, the inclination angle of the fl ow vector, and the theoretical variation range of the inclination angle of the fl ow vector, ranging between 0 and 34°.

Laser pressure welding of Al-Li alloy 2198: effect of welding parameters on fusion zone characteristics associated with mechanical properties

AbstractAl-Li alloy 2198 exhibits good combination of toughness and strength but its application is strongly limited by the poor weldability due to the formation of porosities during fusion-welding. This is the first study proposing and verifying a new approach to produce defect-free laser welds of poorly fusion-weldable Al-Li alloy 2198 with applied external pressure, i.e., feasibility of laser pressure welding to Al-Li alloy 2198 was examined. The microstructures associated with tensile shear behavior of laser pressure welded Al-Li alloy 2198 obtained at various welding parameters were analyzed. The results showed that formation of the welding defect in the weld could be successfully suppressed by applying laser pressure welding, even without shielding gas. Three microstructural zones, including the chill zone, the columnar zone and the equiaxed zone were observed in the fusion zone. Size of fusion zone and area fraction of porosities generally increased with increasing roller pressure and welding heat-input, and they dominantly affected the tensile shear behavior, including the peak load and the failure mode, of the weld.

Metallurgical Failure Analysis of a High-Strength-Steel Drag Chain Conveyor Link

A detailed failure analysis was carried out on a broken chain link made from high-strength manganese steel which failed while in service at a cement factory. Metallographic and microhardness testing revealed the presence of a dual structure within the failed link: a softer low-precipitate chill zone at the outer periphery and a hard and brittle inner structure typified by columnar grain structure and high volume of both inter- and intragranular carbide precipitation. The present failure is believed to have initiated at the outer surface by a contact rolling fatigue action within the softer structure and further augmented by the presence of shrinkage porosity and the inner brittle structure. The development of the observed failure is discussed in terms of microstructure and mechanical properties of the material of manufacture, and practical recommendations are presented at the end of the paper.

Morphology, Mineralogy, and Composition of Sulfide Droplets in Picrodolerite from a Near-Bottom Apophysis of the Yoko-Dovyren Layered Intrusion

The paper presents data on sulfide globules in picrodolerites from a bottom apophysis of the Yoko-Dovyren massif, northern Transbaikalia. Textural features of the rocks indicate that they crystallized at rapid magma cooling. Their composition is similar to that of chilled olivine gabbronorites from the lower contact of the massif. Many droplet-shaped sulfides, which range from 2 to 15 mm, were identified in one of the samples using X-ray computed tomography. The largest of these globules was drilled out and studied in detail to clarify its inner structure, which consists of the main spheroid and a surrounding halo of disseminated sulfides. The main globule and surrounding halo significantly differ in composition (the halo is richer in Cu), as was calculated using the average compositions of the dominant sulfide phases and their relative proportions. The weighted mean (with regard for halo) composition can be assumed as an approximation of the composition of the initial sulfide liquid that was formed near the chill zone of the gabbronorite apophysis from the main intrusive chamber. The Cu content in the initial sulfide corresponds to the results of thermodynamic modeling (with the COMAGMAT-5 program package) of the geochemistry of primitive sulfides in ultramafite rocks from the basal zone of the massif. The differences in the composition of the halo and the main globule indicate the possibility of local migration (within a few millimeters) of the residual sulfide liquids enriched in Cu when the protosulfide melt differentiated. As a physical mechanism that produced the halo, we assumed that the latest sulfide fraction was pressed off into the pore space of rapidly crystallizing olivine orthocumulates.

Columnar-equiaxed transition in continuous casting based on a micro-macro solidification model with long-range solutal mixing

A novel model is proposed to describe the columnar to equiaxed transition (CET) in continuous casting. The model bases on Rappaz and Thevoz’s solute diffusion model for equiaxed dendritic growth, combined with a 1-Dimensional solidification model normal to the slab surface. The unique feature of the proposed model is the combination with a mixing term between interdendritic and extradendritic melt, representing long-range solutal mixing by convection. The model can also be applied to predict equiaxed to columnar transition (ECT), i.e. the chill zone thickness. The model consists of modules such as nucleation, growth kinetics, solute and heat balance, and a solute mixing module. Nucleation is considered with a fixed nucleation undercooling. The growth kinetics of the dendrites are treated according to the LGK model. A finite difference scheme is employed for solving 1-Dimensional heat transfer equations and finally, volume averaged solute balance equations are solved in a staggered scheme. Mixing of inter- and extradendritic liquid is, as a first step, treated ideally fast. When applied to Fe-C binary system with the thermo-physical properties obtained from literature and CALPHAD simulations, the model successfully predicts recalescence, phase fraction evolution, and concentration profiles in different phases. Realistic boundary conditions of the continuous casting process are obtained from macroscopic FEM simulation.

Dependence of cast iron chill from its carbon equivalent

Numerical relation of cast iron chill characteristics (distance of chilled layer H and volume quota of ledeburite in it Qл ) with its carbon equivalent СE was investigared. This data helps to prognosticate with high probability the evolution of the surface chilled layer forming at the production of castings with different thickness from cast iron of various chemical compositions. The object of study is the unalloyed induction melted cast iron with eight variants of chemical composition with carbon equivalent from 3.30 up to 5.53 %. From these cast irons we made the step-by-step castings with steps sizes of 10×60 mm and thickness of 5, 10, 20 and 40 mm. The distance (depth) of chilled layer was measured at the fractures of the castings and gaged on thickness of full chill zone. Ledeburite volume quota was detected by metallographic method using “Nexsys-Image expert pro 3” computer program. According to experimental data, when the casting thickness is 5 and 10 mm the through (at all thickness) full chill is formed at carbon equivalent ≤ 4.08 % and ≤ 3.67 % consequently. At the castings with 20 and 40 mm thickness the zone of full chill is absent, and in this case the chilled layer depth increases with a decrease of carbon equivalent and decreases with an increase of casting’s thickness X. The dependence of H from СЕ have the exponential character and can be described by the equation H = A exp (–k СE ), where A and k are empirical coefficients. Ledeburite volume quota near the contact surface of casting with chiller is near 90 %, but with an increase in the distance from the surface it decreases with different intensity depending on changes of carbon equivalent and casting’s thickness. By mathematical processing of the experimental data received for the distance of 5 mm from the contact surface of the casting with chiller, we have detected that numerical re lation Qл in casting chilled layer with value of CE can be described by the exponential dependence

Dependence of Cast Iron Chill from its Carbon Equivalent

The numerical relation of cast iron chill characteristics (distance of chilled layer H and volume quota of ledeburite in it Ql) with its carbon equivalent СE was investigated. This data helps forecast the evolution of the surface chilled layer forming at the casting production with different thickness from cast iron of various chemical compositions. The study focuses on the unalloyed induction-melted cast iron with eight chemical-composition variants with carbon equivalent from 3.30 up to 5.53%. From these cast irons, step-by-step castings were made with steps sizes of 10 × 60 mm and thickness of 5, 10, 20, and 40 mm. The chilled-layer distance (depth) was measured at the casting fractures and gaged on thickness of full chill zone. Ledeburite volume quota was detected by a metallographic method using the “Nexsys-Image expert pro 3” computer program. According to experimental data, when the casting thickness is 5 and 10 mm, the through (at all thickness) full chill is formed at a carbon equivalent ≤4.08% and ≤3.67%, consequently. At the castings with 20- and 40-mm thickness, the zone of full chill is absent. In this case, the chilled layer depth increases with a decrease of carbon equivalent and decreases with an increase of casting’s thickness X. The dependence of H from CE have the exponential character and can be described by the equation H = Aexp(–kCE), where A and k are empirical coefficients. Ledeburite volume quota near the contact casting surface with chiller is near 90%, but it decreases with different intensity depending on changes of carbon equivalent and casting’s thickness with an increase in the distance from the surface. By mathematical processing of the experimental data received for the 5-mm distance from the contact surface of the casting with chiller, a numerical relation Ql in casting chilled layer with value of CE can be described by the exponential dependence: Ql = 1000(7/(X + 10))exp(–CE).

Diabase Sills in the Outer Zone of the Emeishan Large Igneous Province, Southwest China: Petrogenesis and Tectonic Implications

Compositionally and texturally zoned diabase dykes and sills occur in the outer zone of the Emeishan large igneous province (ELIP) in the southern Guizhou Province, Southwest China. Based on the detailed petrology, whole rock geochemistry, zircon U-Pb geochronology and Hf isotopes and clinopyroxene mineral compositions studies, we investigate a representative diabase sill in the Luodian region with a view to understanding its petrogenesis and tectonic implications. Formed as composite zoned sub-volcanic intrusion, the diabase sill is characterized by gabbros and diabases in the inner zone and amygdaloidal diabases sporadically in the chilled zone within the upper sill margin. The diabasic and gabbroic rocks are composed of quartz-free and quartz-bearing groups. The quartz-free group rocks have low SiO2 (45.7 wt.%-49.5 wt.%), moderate MgO (5.66 wt.%-7.88 wt.%), high TiO2 (2.54 wt.%-3.65 wt.%), and Ti/Y values (536-747), corresponding to high-Ti type rocks. The quartz-bearing group rocks have higher SiO2 (49.8 wt.%-51.7 wt.%) and lower MgO (4.23 wt.%-4.74 wt.%), higher TiO2 (3.16 wt.%-3.63 wt.%), but lower Ti/Y values (399-419) than the quartz-free group ones, and thus belong to the low-Ti type. Both groups of rocks are enriched in LREE and LILE with negative Nb-Ta anomalies, and show broad tholeiitic affinity. The precursor magma of the high-Ti rocks might have originated from a source composed of mantle plume and subcontinental lithosphere mantle components, with minor crustal contamination during ascending. The magma of the low-Ti rocks was produced by mingling of the high-Ti diabasic rocks with minor injected intermediate-acidic magma plugs or blebs, suggesting magma mingling as one of the effective ways to change the high-Ti to low-Ti rocks of the ELIP. The diabasic sill underwent a rapid cooling event probably in response to a rapid tectonic uplift event, which probably occurred in the waning stage of ELIP during transition between the Middle and Late Permian after the domal uplift induced by the mantle-plume or in the Late Jurassic.