Flux Melting Research Articles

A Novel High-Entropy Alloy AlMgZnSnPbCuMnNi with Low Free Corrosion Potential

A novel AlMgZnSnPbCuMnNi high entropy alloy was prepared by flux melting in the atmosphere. The microstructure and the electrochemical performances of the as-prepared alloy were studied by electrochemical workstation, X-ray diffraction and scanning electron microscopy. It was found that the free corrosion potential is as low as-1.33V in the 3.5%NaCl solution in spite of the content of Al, Mg and Zn element of the high entropy alloy is far below than that of the traditional zinc or aluminum sacrificial anode material while the free corrosion current density is 2.93×10-5 A/cm2 which is close to the typical aluminum sacrificial anode material.

ChemInform Abstract: Molten Salt Flux Synthesis and Crystal Structure of a New Open‐Framework Uranyl Phosphate Cs3(UO2)2(PO4)O2: Spectroscopic Characterization and Cationic Mobility Studies.

AbstractYellow single crystals of Cs3(UO2)2(PO4)O2 are prepared by flux melting of the precursor (UO2)3(PO4)2 (H2O)4 using excess CsI as fluxing agent (Pt crucible, 750 °C, 10 h; 7 °C/h cooling rate).

Crustal construction and magma chamber properties along the Eastern Lau Spreading Center

The L-SCAN active-source seismic tomography experiment maps the crustal structure and magmatic system along a 120-km-long section of the back-arc Eastern Lau Spreading Center (ELSC), where the ridge undergoes abrupt changes in morphology and composition associated with increasing proximity to the Tofua volcanic arc. Using this dataset, we picked ~197,000 P-wave travel times from 57 seismic airgun lines recorded at 83 ocean bottom seismograph stations, and inverted for a 3-D P-wave velocity image. The seismic images reveal a prominent, but narrow, seismic low velocity volume (LVV) located beneath all surveyed ridge segments, consistent with the high temperatures and melt of a crustal magmatic system. Crustal magmatic systems thus underlie spreading axes even where previous seismic reflection surveys did not detect magma lens reflectors, accounting for the heat source of high-temperature hydrothermal vents in these areas. The top of the LVV closely follows the ridge axis and steps across three overlapping spreading centers. As the offset of the overlap increases, the LVV becomes increasingly discontinuous across the ridge limbs. Surprisingly, the LVV is as much as twice as wide, but deeper, in the northern part of the ridge system where the crust is thinner, as compared to the LVV beneath the southern segments, where the crust is relatively thicker. The width of the LVV may be modulated by the degree of deep hydrothermal activity or temporal variations in melt supply, and thus may not correlate directly with the average melt flux as indicated by crustal thickness. Over the past 4Myr, the location of the ridge has swept across different mantle compositional domains, and the crust produced at the ridge formed a zoned pattern. The interpretation is that thick, highly porous, volcanic layers with felsic compositions cap regions of thick crust; thinner volcanic layers of basaltic composition cap regions of thinner crust. The zonal pattern indicates that the influence of slab-derived water on crustal construction has substantially decreased over time.

ChemInform Abstract: Synthesis, Structure, and Properties of Ln2Ru3Al15 (Ln: Ce, Gd): Comparison with LnRu2Al10 and CeRu4(Al,Si)15.58.

AbstractAttempts to obtain phase‐pure Ln2Ru3Al15 (Ln: Ce, Gd) from the elements by either flux melting, induction heating, or arc melting show that the latter method is the most suitable one (alumina crucible, final annealing at 1150 °C, 6 d).

Melting of Iron at Earth’s Inner Core Boundary Based on Fast X-ray Diffraction

Earth's core is structured in a solid inner core, mainly composed of iron, and a liquid outer core. The temperature at the inner core boundary is expected to be close to the melting point of iron at 330 gigapascal (GPa). Despite intensive experimental and theoretical efforts, there is little consensus on the melting behavior of iron at these extreme pressures and temperatures. We present static laser-heated diamond anvil cell experiments up to 200 GPa using synchrotron-based fast x-ray diffraction as a primary melting diagnostic. When extrapolating to higher pressures, we conclude that the melting temperature of iron at the inner core boundary is 6230 ± 500 kelvin. This estimation favors a high heat flux at the core-mantle boundary with a possible partial melting of the mantle.

Spasmodic growth during the rapid solidification of undercooled Ag-Cu eutectic melts

A melt fluxing technique has been used to undercool Ag-Cu eutectic alloy by 10–70 K and the subsequent recalescence has been studied using high speed imaging. Spasmodic growth of the solidification front was observed, in which the growth front would make a series of quasi-periodic jumps separated by extended periods during which time growth appeared to arrest. Evidence of this previously unreported mode of growth is presented. The high speed images and microstructural evidence support the theory that anomalous eutectics form by the growth and subsequent remelting of eutectic dendrites.

Along-arc variations in lithospheric mantle compositions in Kamchatka, Russia: First trace element data on mantle xenoliths from the Klyuchevskoy Group volcanoes

We provide results of a detailed study of the first peridotite xenoliths of proven mantle origin reported from Bezymyanny volcano in the Klyuchevskoy Group, northern Kamchatka arc. The xenoliths are coarse spinel harzburgites made up mainly of Mg-rich olivine as well as subhedral orthopyroxene (opx) and Cr-rich spinel, and also contain fine-grained interstitial pyroxenes, amphibole and feldspar. The samples are unique in preserving the evidence for both initial arc mantle substrate produced by high-degree melt extraction and subsequent enrichment events. We show that the textures, modal and major oxide compositions of the Bezymyanny xenoliths are generally similar to those of spinel harzburgite xenoliths from Avacha volcano in southern Kamchatka. However, coarse opx from the Bezymyanny harzburgites has higher abundances of light and medium rare earth elements and other highly incompatible elements than coarse opx from the Avacha harzburgites. We infer that (1) the sub-arc lithospheric mantle beneath both Avacha and Bezymyanny (and possibly between these volcanoes) consists predominantly of harzburgitic melting residues, which experienced metasomatism by slab-related fluids or low-fraction, fluid-rich melts and (2) the degrees of metasomatism are higher beneath Bezymyanny. By contrast, xenolith suites from Shiveluch and Kharchinsky volcanoes 50–100km north of the Klyuchevskoy Group include abundant cumulates and products of reaction of mantle rocks with silicate melts at high melt/rock ratios. The high melt flux through the lithospheric mantle beneath Shiveluch and Kharchinsky may be related to the asthenospheric flow around the northern edge of the sinking Pacific plate; lateral propagation of fluids in the mantle wedge south of the plate edge may contribute to metasomatism in the mantle lithosphere beneath the Klyuchevskoy Group volcanoes.

An investigation on interfacial reaction between in-situ melted AZ91D magnesium alloy and ceramic shell mold during investment casting process

The reaction between ceramic shell investment mold and AZ91D magnesium alloy as well as the related mechanism involved during investment casting process using in-situ melting technique were explored. AZ91D granules were melted in a ceramic shell investment casting mold at 750 °C in an argon protected environment and a melting flux. The interface of adhered investment-AZ91D cast alloy and the residues that appeared on the surface of the castings, as the mold–metal reaction products, were analyzed to determine the morphology, elements and compounds that may have developed due to the reactions. It was discovered that the high process temperature and high affinity of magnesium with oxygen developed cracks in the ceramic shell investment mold. Penetration of molten metal through the cracks also occurred and caused adherence of investment on the casting surface. The results showed that the black residue with a granular morphology has the same microstructure as that of AZ91D alloy and also comprises of MgO and Mg2Si on its surface. The findings revealed that two types of products formed on the shell surface due to the mold–metal reaction. The first product formed on the surface as a result of the reaction between AZ91D alloy and the binder producing MgO and MgAl2O4. The second product formed because of the penetration of Mg into the ceramic shell investment mold followed by reaction with oxygen bearing materials forming MgO and Mg2Si.

Effect of the Separation of Large Limonite Ore Particles in the Granulation Process of Sinter Raw Materials

Sintering with large amount of limonite generally requires higher fuel consumption, either due to the dehydration of combined water or the evaporation of more added water. Although limonite can accelerate melt formation, the sintering strength indexes are in lower level on the contrary, proved to have much to do with the excessive assimilation.In order to improve the sintering behavior of sintering mix when large amount of limonite were used, a simplified method named separating large particles of limonite from granulation was investigated by measuring the bonding strength using quasi-particles on the base of confirming influence of excessive assimilation on effective liquid phase of limonite, and calculating changes in properties of sintering mix for moisture transferring. The results obtained were summarized as follows:Limonite nuclei adversely influenced bonding strength of quasi-particles mainly by the effective liquid phase, which was determined by volume decrease for penetration and viscosity increment by less fluxed melt, separation of limonite nuclei to reduce the contact interface is helpful in improving bonding of sintered body, and the separation ratio was suggested be within certain range by melt distribution in the whole bed. Less accumulation of condensed water and partial absorption by ungranulated dry limonite resulted in smaller increment in effective mean size and less decrement in void fraction, indicating better bed permeability.

Dynamic topography of the western Great Plains: Geomorphic and 40Ar/39Ar evidence for mantle-driven uplift associated with the Jemez lineament of NE New Mexico and SE Colorado

The causal mechanisms for the onset and patterns of post-Miocene erosion of the western Great Plains remain the subject of an enthusiastic debate concerning the roles of climatically modulated geomorphic parameters and tectonic rock uplift as drivers of long-term erosion. This study distinguishes between these drivers on the plains of New Mexico and Colorado, where post-Miocene erosion and late Cenozoic volcanism of the Jemez lineament have produced distinctive modern landscapes characterized by deep bedrock canyons and inverted, basalt-capped mesas. The 40Ar/39Ar ages of basalt-capped paleosurfaces define an episodic eruption history in the Raton-Clayton and Ocate volcanic fields and help to quantify patterns, amounts, and rates of differential erosion. Several data sets indicate patterns of NE-trending geologic features that require explanation, including: (1) crude volcanic “belts” of similar age, (2) parallel NE-oriented erosional escarpments retreating toward the NW, (3) differential denudation rates increasing systematically NW from a NE-trending hinge line of “low to no” erosion on the Great Plains, (4) a NE-trending zone of broad (50–100 km) convexities in stream profiles identified by an analysis of strath terraces and channel steepness (ksn), (5) reorganization of stream networks that took advantage of an apparent relative base-level fall in the SE, and (6) an ∼150-km-long, 40Ar/39Ar-dated composite paleosurface that has been tilted 64 millidegrees/Ma since 3.4 Ma. Our synthesis of new 40Ar/39Ar geochronology with new calculations of regional surface denudation, channel steepness, and tilt rates shows that post-Miocene patterns of landscape evolution are best interpreted as related to dynamic uplift along the NE-trending Jemez lineament, with second-order impacts from climate-driven geomorphic variables. We interpret this dynamic uplift to be ultimately due to changing mantle structure and buoyancy with associated crustal melt flux.

Heat-Transfer Phenomena Across Mold Flux by Using the Inferred Emitter Technique

An investigation was carried out to study the heat-transfer phenomena across mold flux film by using infrared emitter technique (IET). With IET, it is possible to develop the mold fluxes with a liquid layer at the top and a solid layer in contact with copper mold with the degree of varying crystallization. The dynamic crystallization and melting process of the mold fluxes as well as their effects on the overall heat-transfer rate in the mold were successfully conducted. The single hot thermocouple technique (SHTT) was also employed in this investigation to study the melting and crystallization behaviors of mold fluxes for the interpretation of IET results. The results suggested that the interfacial thermal resistance between the solidified mold flux and copper mold would significantly influence the heat-transfer rate in continuous casting and the melting of the mold flux tends to enhance the overall heat-transfer rate. The technique established in this article by utilizing the IET can be well applied to the investigation of mold flux thermal properties, which in turn gives guidelines for the design of new mold flux for continuous casting.

Flux of carbonate melt from deeply subducted pelitic sediments: Geophysical and geochemical implications for the source of Central American volcanic arc

We determined the fluid‐present and fluid‐absent near‐solidus melting of an Al‐poor carbonated pelite at 3–7 GPa, to constrain the possible influence of sediment melt in subduction zones. Hydrous silicate melt is produced at the solidi at 3–4 GPa whereas Na‐K‐rich carbonatite is produced at the solidi at ≥5 GPa for both starting compositions. At ≥5 GPa and 1050°C, immiscible carbonate and silicate melts appear with carbonate melt forming isolated pockets embedded in silicate melt. Application of our data to Nicaraguan slab suggests that sediment melting may not occur at sub‐arc depth (∼170 km) but carbonatite production can occur atop slab or by diapiric rise of carbonated‐silicate mélange zone to the mantle wedge at ∼200–250 km depth. Flux of carbonatite to shallower arc‐source can explain the geochemistry of Nicaraguan primary magma (low SiO2and high CaO, Ba/La). Comparison of carbonate‐silicate melt immiscibility field with mantle wedge thermal structure suggests that carbonatite might temporally be trapped in viscous silicate melt, and contribute to seismic low‐velocity zone at deep mantle wedge of Nicaragua.

Granitic Pegmatites as Sources of Strategic Metals

Rare-element granitic pegmatites are well recognized for the diversity and concentrations of metal ores that they host. The supply of some of these elements is of concern, and the European Commission recently designated metals such as tantalum and niobium as “critical materials” or “strategic resources.” Field relationships, mineral chemistry, and experimental constraints indicate that these elements are concentrated dominantly by magmatic processes. The granitic melts involved in these processes are very unusual because they contain high concentrations of fluxing compounds, which play a key role at both the primary magmatic and metasomatic stages. In particular, the latter may involve highly fluxed melts rather than aqueous fluids.

Simulating Heinrich event 1 with interactive icebergs

During the last glacial, major abrupt climate events known as Heinrich events left distinct fingerprints of ice rafted detritus, and are thus associated with iceberg armadas; the release of many icebergs into the North Atlantic Ocean. We simulated the impact of a large armada of icebergs on glacial climate in a coupled atmosphere–ocean model. In our model, dynamic-thermodynamic icebergs influence the climate through two direct effects. First, melting of the icebergs causes freshening of the upper ocean, and second, the latent heat used in the phase-transition of ice to water results in cooling of the iceberg surroundings. This cooling effect of icebergs is generally neglected in models. We investigated the role of the latent heat by performing a sensitivity experiment in which the cooling effect is switched off. At the peak of the simulated Heinrich event, icebergs lacking the latent heat flux are much less efficient in shutting down the meridional overturning circulation than icebergs that include both the freshening and the cooling effects. The cause of this intriguing result must be sought in the involvement of a secondary mechanism: facilitation of sea-ice formation, which can disturb deep water production at key convection sites, with consequences for the thermohaline circulation. We performed additional sensitivity experiments, designed to explore the effect of the more plausible distribution of the dynamic icebergs’ melting fluxes compared to a classic hosing approach with homogeneous spreading of the melt fluxes over a section in the mid-latitude North Atlantic (NA) Ocean. The early response of the climate system is much stronger in the iceberg experiments than in the hosing experiments, which must be a distribution-effect: the dynamically distributed icebergs quickly affect western NADW formation, which synergizes with direct sea-ice facilitation, causing an earlier sea-ice expansion and climatic response. Furthermore, compared to dynamic-thermodynamic icebergs, a homogeneous hosing overestimates the fresh water flux in the Eastern Ruddiman belt, causing a fresh anomaly in the Eastern North Atlantic, leading to a delayed recovery of the circulation after the event.

Research on Lagging Melt Phenomenon and Influencing Factors of Flux Cored Arc Welding

Lagging melt phenomenon is the special phenomenon of flux cored arc welding, studying lagging melt phenomenon is very valuable for the design and improvement of flux cored wire. Used digital camera technology, recorded the lagging melt phenomenon of acid、basic and metallic slag systems flux cored arc welding in CO2 protective atmosphere. Analyzed its mechanism and influencing factors of lagging melt phenomenon. The results shows that lagging melt phenomenon under low welding criterion is not obvious in comparison to high welding criterion but still shows lagging melt tendency. Under high welding criterion lagging melt degree increases and metal droplet separated from lagging melt flux core forms separated transfer. Under same welding criterion, lagging melt degree of basic slag system is maximum, acid slag takes the second place and metallic slag system is minimum.

Rapid magmatic processes accompany arc–continent collision: the Western Bismarck arc, Papua New Guinea

New U–Th–Ra, major and trace element, and Sr–Nd–Pb isotope data are presented for young lavas from the New Britain and Western Bismarck arcs in Papua New Guinea. New Britain is an oceanic arc, whereas the latter is the site of an arc–continent collision. Building on a recent study of the Manus Basin, contrasts between the two arcs are used to evaluate the processes and timescales of magma generation accompanying arc–continent collision and possible slab detachment. All three suites share many attributes characteristic of arc lavas that can be ascribed to the addition of a regionally uniform subduction component derived from the subducting altered oceanic crust and sediment followed by dynamic melting of the modified mantle. However, the Western Bismarck arc lavas diverge from the Pb isotope mixing array formed by the New Britain and the Manus Basin lavas toward elevated 208Pb/204Pb. We interpret this to reflect a second and subsequent addition of sediment melt at crustal depth during collision. 238U and 226Ra excesses are preserved in all of the lavas and are greatest in the Western Bismarck arc. High-Mg andesites with high Sr/Y ratios in the westernmost arc are attributed to recent shallow mantle flux melting at the slab edge. Data for two historical rhyolites are also presented. Although these rhyolites formed in quite different tectonic settings and display different geochemical and isotopic compositions, both formed from mafic parents within millennia.

New Mössbauer measurements of Fe3+/ΣFe in chromites from the mantle section of the Oman ophiolite: evidence for the oxidation of the sub-oceanic mantle

AbstractRoom temperature Mössbauer and electron-probe measurements of Fe3+/ΣFe in chromite from the mantle section of the Oman ophiolite define two groups of samples: a low Fe3+/ΣFe group (with Fe3+/ΣFe = 0.21–0.36) have cr# = Cr/(Cr + Al) in the range 0.49–0.75, whereas a smaller more geographically localized high Fe3+/ΣFe group (with Fe3+/ΣFe = 0.71–0.78) have a more restricted range of cr# ratios of 0.72–0.75. The low Fe3+/ΣFe chromitites have very variable Fe3+/ΣFe ratios. They are thought to have crystallized from melts that have interacted with depleted mantle and thereby acquired their variable Fe3+/ΣFe ratio. The high Fe3+/ΣFe chromitites are restricted to one small area of the mantle and their high oxidation state is thought to be post magmatic. They are either the product of later heating, related to melt flux or interaction with a later oxidising melt. A difference in oxygen fugacity between the MORB-depleted harzburgite host, which is at the quartz–fayalite–magnetite (QFM) buffer and the later chromite-bearing melts (QFM + 2) implies that there is a real difference in the oxidation state of the MORB and arc-magma sources.

Sensitivity of a distributed temperature-radiation index melt model based on AWS observations and surface energy balance fluxes, Hurd Peninsula glaciers, Livingston Island, Antarctica

Abstract. We use an automatic weather station and surface mass balance dataset spanning four melt seasons collected on Hurd Peninsula Glaciers, South Shetland Islands, to investigate the point surface energy balance, to determine the absolute and relative contribution of the various energy fluxes acting on the glacier surface and to estimate the sensitivity of melt to ambient temperature changes. Long-wave incoming radiation is the main energy source for melt, while short-wave radiation is the most important flux controlling the variation of both seasonal and daily mean surface energy balance. Short-wave and long-wave radiation fluxes do, in general, balance each other, resulting in a high correspondence between daily mean net radiation flux and available melt energy flux. We calibrate a distributed melt model driven by air temperature and an expression for the incoming short-wave radiation. The model is calibrated with the data from one of the melt seasons and validated with the data of the three remaining seasons. The model results deviate at most 140 mm w.e. from the corresponding observations using the glaciological method. The model is very sensitive to changes in ambient temperature: a 0.5 °C increase results in 56 % higher melt rates.

Inter-element fractionation of highly siderophile elements in the Tonga Arc due to flux melting of a depleted source

Highly siderophile element concentrations (HSEs: Os, Ir, Ru, Pt, Pd, and Re) have been determined for a suite of fresh, submarine mafic lavas from the northern Tonga Arc front and the nascent backarc Fonualei Spreading Centre (FSC). Prior melt depletion of the Tongan mantle wedge combined with a high degree of fluid fluxed melting is thought to have produced boninitic magmas at several arc and FSC locations. As such, this arc system provides an opportunity to assess the fluid mobility of HSEs and to investigate the effects of fluid-induced melting and prior melt depletion on HSE behaviour during both mantle melting and magma evolution.Tongan lavas display extreme enrichment of Pt (2.5–32ng/g) and Pd over Os (0.002–0.6ng/g), Ir, and Ru, significantly greater than basalts from mid-ocean ridges. Magma evolution increases the degree of fractionation, resulting in the highest recorded Pt/Ru ratios (>300) in arc front samples with MgO <8 wt.%. This increasing fractionation is due to the mild incompatibility of Pt and Pd, and concurrent compatibility of Ru, during sulphide undersaturated magma evolution. However, the fractionation of Pt and Pd from Os, Ir, and Ru is observed in the highest MgO samples, indicating source inheritance. Prior melt depletion of the mantle and elevated oxygen fugacity both increase the likelihood of complete consumption of sulphide in the source during melting, which typically leads to melts with high concentrations of all the HSE. Indeed, modelling indicates that 25% aggregate partial melting of a depleted MORB-mantle source, proposed for the Tonga Arc, will lead to complete base-metal sulphide consumption unless there is considerable addition of S by the slab flux (at least 200μg/g). Although source enrichment of Pt, Pd, and Re by slab fluids may take place, the fractionation of Pt and Pd from Os, Ir, and Ru can largely be explained by relatively low-temperature, yet high-degree, melting of fluid-fluxed melt-depleted mantle. The high Pt and Pd contents can be produced by the exhaustion of sulphide in the source, while the presence of Ru–Os–(Ir) alloys or sulphides (e.g. laurite) associated with Cr-spinel can explain Os, Ir, and Ru retention in the source residue. Such phases have been documented in fluid-fluxed sub-arc mantle from ophiolites.Osmium isotopes co-vary negatively with Os abundance and thus appear to be dominated by shallow level contamination. The most Os-rich samples, however, have 187Os/188Os ratios (0.126–0.132) which are typical of DMM and MORB, suggesting an indistinguishable flux of radiogenic Os from the slab. The significant fractionation of Pt and Re from Os in arc settings will lead, over time, to elevated 186Os and 187Os which may be relevant to the observed enrichments of these isotopes in some mantle regions. In addition, the differing behaviour of Ru and Ir, and the implication of a mantle source containing Ru-rich microphases, may have consequences for the estimation of the HSE composition of primitive upper mantle.

Near-surface climate and surface energy budget of Larsen C ice shelf, Antarctic Peninsula

Abstract. Data collected by two automatic weather stations (AWS) on the Larsen C ice shelf, Antarctica, between 22 January 2009 and 1 February 2011 are analyzed and used as input for a model that computes the surface energy budget (SEB), which includes melt energy. The two AWSs are separated by about 70 km in the north–south direction, and both the near-surface meteorology and the SEB show similarities, although small differences in all components (most notably the melt flux) can be seen. The impact of subsurface absorption of shortwave radiation on melt and snow temperature is significant, and discussed. In winter, longwave cooling of the surface is entirely compensated by a downward turbulent transport of sensible heat. In summer, the positive net radiative flux is compensated by melt, and quite frequently by upward turbulent diffusion of heat and moisture, leading to sublimation and weak convection over the ice shelf. The month of November 2010 is highlighted, when strong westerly flow over the Antarctic Peninsula led to a dry and warm föhn wind over the ice shelf, resulting in warm and sunny conditions. Under these conditions the increase in shortwave and sensible heat fluxes is larger than the decrease of net longwave and latent heat fluxes, providing energy for significant melt.