High Homogenization Temperatures Research Articles

Refinement mechanism of cerium addition on solidification structure and sigma phase of super austenitic stainless steel S32654

• Ce addition could modify MgO and MnS into Ce 2 O 3 and Ce 2 O 2 S in S32654. • Ce addition leads to noticeable refinement of both dendrite structure and σ phase. • Effective Ce-bearing inclusions could serve as nucleation cores of γ and σ phase. • Solute Ce markedly enhances undercooling degree, further refining dendrite structure. • Solute Ce promotes σ phase nucleation, while dendrite refinement limits its growth. The influence of Ce addition on the solidification structure and σ phase of super austenitic stainless steel S32654 was systematically investigated via microstructural characterization and thermodynamic calculation. The results indicate that a small addition of Ce could modify MgO and MnS into Ce-bearing inclusions Ce 2 O 3 and Ce 2 O 2 S. Ce addition led to noticeable refinement of both the dendrite structure and σ phase. The refinement mechanism could be attributed to the combined actions of effective Ce-bearing inclusions and solute Ce. Effective Ce-bearing inclusions could serve as heterogeneous nucleation cores of austenite as well as σ phase, which provided a favorable prerequisite for their refinement. Solute Ce significantly enhanced the undercooling degree of the system, further promoting dendrite structure refinement. Meanwhile, solute Ce improved the eutectic precipitation conditions of σ phase and further promoted its nucleation, while the dendrite refinement limited its growth space. Finally, more fine and dispersed σ phase particles formed in S32654 with Ce addition. The refinement of dendrite structure and σ phase will reduce the temperature and time required for high-temperature homogenization, which is beneficial to the hot working of this steel.

Diagenetic Fluid and Its Impact on Sandstone Reservoirs in the Southern Boxing Sag, Dongying Depression, Bohai Bay Basin, China

Diagenesis typically exerts a crucial impact on the formation of high-quality sandstone reservoirs in the Eocene Shahejie Formation, Dongying Depression. To better understand the formation process of petrophysical properties, this research conducts petrographic and geochemical analyses to investigate the nature of diagenetic fluids. Petrographic observations suggest that the dominant cements are carbonate, authigenic quartz, and clay minerals, accompanied with the dissolution of feldspar and calcite. The homogenization temperature of aqueous inclusions in quartz overgrowth usually exceeds 90°C corresponding to the maturity of organic matter. Quartz overgrowths contain higher amounts of CaO and Al2O3 than detrital quartz. This indicates that the siliceous fluid mainly originates from the dissolution of feldspar. Moreover, the conversion of clay minerals also provides trace amounts of silica into pore water during the burial process. Carbonate cements consist of early-stage calcite as well as late-stage Fe-calcite and ankerite. Calcite with relatively higher MnO proportions shows yellow luminescence and dissolution signs. Fe-calcite and ankerite cements have a higher homogenization temperature than that of quartz overgrowth and mainly concentrate in FeO and MgO as well as contain a small amount of Na+, K+, and Sr2+. The rare earth element (REE) pattern of bulk mudstone and carbonate cements as well as C–O isotopic evidences indicate that the diagenetic fluids of carbonate cementation are primarily controlled by the adjacent mudstone, whereas mineral dissolution and altered clay minerals in sandstone provide additional cations for the local reprecipitation of late-stage carbonate. Therefore, diagenetic fluids within sandstone reservoirs are typically subject to alkaline–acid–alkaline conditions and are influenced by internal sources in a closed system. Compaction significantly reduces the pore space of sandstone reservoirs in the Boxing Sag. Carbonate cementation further increases the complexity of pore structure and obeys the principle of mass balance.

High‐sulfidation epithermal–porphyry transition in the Kumbokarno Prospect, Trenggalek district, East Java, Indonesia: Constraints from mineralogy, fluid inclusion, and sulfur isotope studies

AbstractAn indication of high‐sulfidation epithermal–porphyry transition was observed in the Kumbokarno prospect, East Java, Indonesia. The prospect is composed of two Middle Miocene intrusions with tonalitic and dioritic compositions. Tonalite, the main host‐rock was subjected to argillic, advanced argillic, and vuggy quartz alteration, whereas the juxtaposing diorite was subjected to peripheral propylitic alteration. Three types of vein exist in the research area, which are massive quartz, comb quartz, and stockwork vein. In addition, supergene alteration represented by goethite and hematite pervasively superimposed both the hydrothermal alteration and mineralization. Fluid inclusion petrography and microthermometry analysis on three types of quartz veins distinguished primary fluid inclusions into two groups, that is, V30 group composed of vapor (30 vol%)–liquid (70 vol%), and the second group V30H group composed of vapor (30 vol%)–halite (30 vol%)–liquid (40 vol%). The homogenization temperatures of both the groups show a similar range of ca. 350–480°C, but the V30H group has significantly higher salinity (35–50 wt% NaCl eq.) compared to the V30 group (10–20 wt% NaCl eq.). In terms of the vein types, the massive quartz vein has the highest homogenization temperatures, followed by the comb quartz vein and lastly the stockwork veins. The presence of alunite and its sulfur isotope compositions, δ34S = 19.6 (σ = 2.1‰), indicate acidic pH and presence of SO42− in the hydrothermal fluids. The prospect is an intrusion‐centered magmatic‐hydrothermal system reflecting the porphyry‐epithermal transition. The fluid inclusions with high homogenization temperatures up to 480°C and high salinity up to 50 wt% NaCl eq. also support the transition of porphyry to high‐sulfidation epithermal mineralization. The presence of two different types of primary fluid inclusions suggests that boiling process occurred and separated the original magmatic fluid into the liquid and vapor phases. More, this fluid underwent dilution and mixing with meteoric waters. The migration of both the fluids were likely unrelated to the formation of the advanced argillic–argillic alteration halo because the quartz veins cut across this alteration. The prospect was later subjected to intensive weathering process that altered most of the sulfides into iron oxides and hydroxides. Small amounts of copper and minor gold were detected, especially in the iron oxides and hydroxides ones with colloform and bladed textures. The Kumbokarno prospect evidences the potential for high‐sulfidation to porphyry deposits at the Southern Mountain Arc, Indonesia.

Исследование высокотемпературной гомогенизации монокристаллического никелевого жаропрочного сплава 3-го поколения

High-alloyed nickel-based superalloys used for casting of single crystal blades of aircraft gas-turbine engines have to be subjected to a long-term high-temperature homogenization annealing for dissolution of nonequilibrium γ′-eutectics and smoothing of dendritic segregation of alloying elements. Single crystal nickel-based superalloy of the 3-rd generation CMSX-10 developed by Cannon-Muskegon corporation for casting highly loaded uncooled single crystal blades of the first stage of a high pressure turbine of an aviation gas turbine engine Trent 800 belongs to such alloys. In the present work, the processes occurring during high-temperature homogenization annealing of this alloy have been investigated. It is shown that the kinetics of dissolution of nonequilibrium γ′-eutectics strongly depends on temperature: in the range of 1340 – 1360 °C the dissolution rate increases by about an order of magnitude with increasing temperature by 10 °C. Two types of homogenization annealing with a stepwise increase of temperature proposed for CMSX-10 by Cannon-Muskegon have been investigated: a long 45-hour annealing with 10 steps of temperature increase and a shortened 20-hour annealing with 6 temperature steps. The change in the solidus temperature of the alloy during the homogenization was studied by the method of measurement of the specific electrical resistance. It is shown, that during homogenization annealing of the both types the nonequilibrium eutectics is completely dissolved, and a longer 45-hour annealing provides a deeper chemical homogenization of the alloy. This is especially important for such alloying element as rhenium, which has a high segregation coefficient and very slow diffusion mobility in nickel. Deeper homogenization provides better thermal stability of the alloy microstructure and consequently higher long-term creep strength. A negative effect of high-temperature homogenization is increased porosity resulting from the dissolution of γ′-eutectics. Homogenization porosity can be reduced by optimizing the alloy composition and reducing the fraction of nonequilibrium γ′-eutectics.

Role of homogenization on tensile properties and microstructures in a dilute Mg–Zn–Ca–Mn alloy sheet

The effect of homogenization on microstructures and tensile properties in a dilute Mg–Zn–Ca–Mn alloy sheet was investigated. High-temperature homogenization at 480 °C dissolved eutectic intermetallic phases before rolling; however, there was a significant growth of αMn precipitates, resulting in a coarse grain structure in the rolled and annealed alloy sheet. Although rolling without homogenization or after low-temperature homogenization led to a slight increase in the fraction of intermetallic phases in the annealed state, fine grain structure was achieved due to finely dispersed αMn precipitates. Especially, fine average grain size of 8.9 μm was obtained without any homogenization, and the annealed sheet exhibited good 0.2% tensile yield strength and elongation to failure of 176 MPa and 23.4% along the rolling direction. Unfortunately, the annealed sheet had an in-plane yield anisotropy, but the moderate 0.2% tensile yield strength of 142 MPa could be kept even along the transverse direction due to its fine grain structure.

Entrapment history of aqueous fluids in Archean cherts from the Barberton Greenstone Belt, South Africa

We performed fluid inclusion microthermometric analyses of four cherts and one silicified anhydrite from various successions of the Mesoarchean Barberton Greenstone Belt, South Africa, and constrained the entrapment conditions and provenance of fluids that were incorporated during different magmatic or tectono-thermal events. Major saline aqueous fluid inclusion assemblages in cherts from the 3.2 Ga old Mendon Formation (Barite Valley Syncline, Power Line Road) and from the 3.42–3.45 Ga old uppermost Hooggenoeg Formation (Buck Reef Chert) correspond to fluids incorporated during metamorphism. Their documented P-T conditions compare well with reported petrologic constraints. In Buck Reef chert we also found a distinctive suite of inclusions with high salinities and low homogenization temperatures (61–118 °C). This is in agreement with a hydrothermal formation of these fluids at subseafloor conditions. Finally, we investigated quartz in a silicified anhydrite and its sandstone host from the Stolzburg Syncline (Moodies Group, ca. 3.2 Ga). One major inclusion assemblage in the evaporite and in adjacent quartz within the embedding sandstone share the P-T range observed for the cherts from the Mendon Fm. Its incorporation is postdating the silicification process. We also found two higher temperature inclusion types that favor a magmatic origin. In particular, one of these inclusion suites is only observed in quartz within the matrix and likely mirrors trapping of brines associated with magmatic fluids predating sedimentation of the sandstone, e.g., from the potential magmatic source region of the quartz. Our results indicate the presence of coexisting aqueous fluids in cherts derived from distinct source environments, spanning an age range of several 100 Ma on a grain scale. The earliest hydrothermal aqueous inclusions were documented in a Buck Reef chert (3.42–3.45 Ga), whereas the majority of aqueous fluids are metamorphic in origin and likely related to the documented 3.23 Ga and 3.1 Ga tectono-thermal events. Our findings demonstrate that constraining environmental conditions by the volatile record of Archean cherts requires analyses on inclusion, not grain scale.

Strength-ductility synergy in Mg98.3Y1.3Ni0.4 alloy processed by high temperature homogenization and rolling

A new Mg98.3Y1.3Ni0.4 alloy containing long period stacking ordered (LPSO) phases with good strength-ductility synergy was prepared by high temperature homogenization and rolling, which possesses a high ultimate tensile strength of 320 MPa and elongation of 17.0% and low work hardening rate during tensile deformation. Bulk LPSO phases with lamellar morphology exist in original grains after homogenization. Refined grains, broken LPSO phases and high-density geometrically necessary dislocations provide a good strength for as-rolled alloy with the strength increment of 146.3 MPa, 51.7 MPa and 68.3 MPa, respectively. Good ductility and low work hardening rate are attributed to weak basal texture, activation of non-basal slips with high Schmid factors and annihilation of high-density dislocations. In situ tensile testing result shows deformation coordination by non-basal slips, deformation twinning, grain rotation and absorption of plastic deformation energy by LPSO phases, which suggests a good ductility as well.

Atomic Layer Deposition (ALD) of Ultra-Thin Diffusion Barriers on ZnSe Microparticles for Phase Stability in Chalcogenide Glasses for Mid-Infrared Optics

ZnSe embedded chalcogenide glass (ChG) composites are optically active in the mid-infrared (IR) and are ideal for niche applications in medical diagnosis, military missile heat-sensing, and chemical identification. The embedded ZnSe crystals play a critical role in providing lasing activity while the ChG - As2S3-xSex matrix, acts as a host that can be drawn into fiber and provides the necessary mid-IR transparency. However, during synthesis, the ZnSe particles are prone to dissolution in the As2S3-xSex matrix due to a high temperature (650 oC) melting and homogenization process. Here we demonstrate that a thin amorphous barrier layer of Al2O3 deposited using atomic layer deposition (ALD) on ZnSe microparticles 5-10 mm in average diameter is successful to prevent ZnSe dissolution in the As2S3-xSex matrix even after extended melting and homogenization at 650 oC for 8 hours. This talk will highlight some of the key process innovations required to overcome challenges of ALD on powdered components for functionalizing and enhancing performance of multiphasic glasses for optical applications.Amorphous aluminum oxide (Al2O3) was deposited using alternate pulses of trimethyl aluminum and H2O on 1 gm batch size ZnSe using a customized rotary barrel reactor inside a viscous-flow ALD furnace attached to a quadrupole mass spectrometer (QMS). The temperature of deposition was kept at 180 oC and the number of cycles were varied from 100 to 300 cycles. The ZnSe particles were sieved to an average size of 5-10 mm and a maximum size ≤ 20 mm. The coated particles were characterized by x-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM). The crystallinity of the ZnSe-As2S3-xSex glasses were evaluated using x-ray diffraction (XRD) and their composition stability spatially mapped across individual ZnSe particles embedded in As2S3-xSex matrix using Raman microspectroscopy.Whereas 100 ALD cycles provide partial protection to dissolution for the ZnSe in As2S3-xSex, a 300 cycle ALD Al2O3 on ZnSe particles is sufficient to provide phase and composition stability to the ZnSe embedded As2S3-xSex glass. Through our investigation, we exemplify the efficacy and potential of ALD of ZnSe powder in improving the stability of optical materials while still achieving optimal mid-IR lasing and transparency.

Cold sintering of the ceramic potassium sodium niobate, (K0.5Na0.5)NbO3, and influences on piezoelectric properties

Cold Sintering was applied to densify a Potassium-Sodium Niobate solid solution composition, 0.5KNbO3-0.5NaNbO3 (KNN); the process uses a transient chemical sintering aid, moderate pressure (400 MPa), and temperatures between 230–300 °C to obtain ceramics of ∼92 to 96 % theoretical density. Typically, sintering temperatures between ∼1000−1050 °C are required to density KNN using conventional methods. In this paper, the densification was investigated during heating, particularly the shrinkage in the first 60 min of the cold sintering process. The low-field dielectric and electrical properties of the resulting ceramics were found to be comparable to conventionally sintered KNN. Electric fields up to 80 kV/cm could be applied, however the ceramics showed pinched hysteresis loops, even after poling over a wide range of temperatures and electric fields. A Rayleigh analysis was used to investigate domain dynamics and high reversible permittivity. The irreversible behavior was an order of magnitude lower than in conventionally sintered KNN, likely associated with defect pinning of ferroelectric domains. A Transmission Electron Microscopy (TEM) study revealed a high density of line defects in most grains; dislocations in the grains limit poling and domain wall movement, thus suppressing both the piezoelectric properties and the hysteresis. Furthermore, TEM observations indicated crystalline grain boundaries that were faceted with terrace kink ledges. These observations point to the importance of the initial powder optimization and grain boundary diffusion when using cold sintering to prepare ceramics that are intended to show bulk cooperative properties such as ferroelectricity. The impact of limited high temperature homogenization of bulk diffusional processes is discussed.

Early-stage marine dolomite altered by hydrothermal fluids in the Middle Permian Maokou Formation in the eastern Sichuan Basin, Southern China

Deciphering the dolomitization process is the key to understanding the formation of massive dolostones on shallow-marine platforms, it also improves our understanding of dolostone reservoirs. Hydrothermal fluids are suggested to be a potential mechanism for dolomitization; however, determining whether hydrothermal fluids are responsible for dolomitization or the recrystallization of an early dolostones is poorly understood. The dolomite of Maokou Formation (Guadalupain) in the eastern part of the Sichuan Basin is a good case study on the hydrothermal dolomitization and recrystallization. Based on petrographic observation, the massive dolostone (MD) consists of fine-crystalline dolomite (D1), fine to medium crystalline dolomite (D2) and coarse-crystalline dolomite (D3), and the patchy dolostone (PD) which is composed of medium to coarse dolomite with an euhedral to subhedral texture. Since the fine-crystalline dolomite is cross-cut by low amplitude stylolites, and is composed of euhedral dolomite with a dull red luminescence, dolomitization is interpreted to have occurred in near surface condition. While the Fe, Mn, and ∑REE concentrations, δ13CVPDB values, 87Sr/86Sr ratios, and REE Pattern of D1 are comparable to those of the coexisting limestone, and the δ18OVPDB values are slightly higher than that of the coeval limestone, indicating that the dolomitization fluid of D1 was derived from Middle Permian seawater. In contrast, zebra fabrics and saddle dolomites are common in D2 and D3, and their geochemical characteristics and cathluminescence are quite different from those of D1 but they are similar to those of the saddle dolomites. Besides, the fluid inclusions in D2 and D3 have high homogenization temperatures and salinities, which are also similar to those of the saddle dolomite. Moreover, the D2 shows an inequigranular texture, and there are no obvious boundaries between D1, D2 and D3. Therefore, the D2 and D3 were recrystallized upon D1 by hydrothermal fluids related to the Emeishan magmatism. The patchy dolostone exhibits a non-stoichiometric composition and low degree of cation ordering, suggests rapid and incomplete dolomitization. The dolomitization of PD is interpreted to be the replacement caused by hydrothermal fluids as the PD exhibits negative δ18OVPDB values, high homogenization temperatures and salinity, positive Eu anomalies and REE Patterns similar to those of the saddle dolomites. The porosity and stoichiometry of the D1 are higher and lower, respectively, than those of D2 and D3, and the vugs are almost entirely filled. Thus, the hydrothermal fluids were destructive for the formation of the dolostone reservoir of Maokou Formation in the study area.

The effect of heat treatment on the structure and mechanical properties of cold-rolled sheets made of Al – Cu – Mn alloys with varying copper to manganese ratios

This paper presents the results of analysis of the structure and properties of the commercial alloy 1201 (Cu:Mn=18,3) and the model alloy 2Mn2Cu (Cu:Mn =1,1) both in the cast state and after various modes of thermodeformation processing, including annealing at temperatures of 250–400 oC. It is shown that even after high-temperature homogenization at 540 oC, the ingot of alloy 1201 is not able to undergo high-quality cold deformation, and therefore the production of semi-finished products requires mandatory hot rolling. At the same time, cold-rolled sheets with a reduction ratio of 95% were obtained from the 2Mn2Cu alloy ingot without any intermediate annealing. The calculation method in the Thermo-Calc soft-ware shows that with an increase in temperature to 400 oC, more than 8 wt.% of the Al20Cu2Mn3 phase dispersoids are formed in the model alloy, which is more effective for containing the recrystallization process than the Al2Cu phase precipitates, which in thepredominant amount (~7 wt.% ) are formed in alloy 1201. The calculation results were confirmed by electron microscopy. After cold rolling, the structure of both alloys contains compact inclusions of intermetallides, and the grain structure shows a fibrous character. After processing according to the modes T, T1, T2 (T4, T6, T7) and annealing, the grade alloy underwent recrystallization at the stage of solution treatment, and after annealing at 400 oC, a coarsening of the secondary Al2Cu phase was observed. The grain structure of the model alloy after step annealing up to 400 oC remained unchanged, due to the presence of fine Al20Cu2Mn3 particles (with average size less than 100 nm). This difference especially affects the mechanical properties. In the state of maximum hardening, alloy 1201 has an advantage (UTS = 431 MPa, YS = 310 MPa, HV = 140). But after annealing at 400 oC strength properties degrade to the level of UTS =227 MPa, YS=86 MPa, HV=55. After step-by-step annealing up to 400 oC, the model alloy underwent a slight softening in terms of UTS value (371 MPa in the cold-worked state versus 277 MPa after annealing), but at the same the elongation increased from 2.7 to 11.5%. Based on the results of the work, it can be argued that the ternary model alloy 2Mn2Cu is a promising matrix for the development of heat-resistant aluminum alloys that do not require homogenization and quenching.This research was funded under Grant No. 20-19-00249 by the Russian Science Foundation.

Thermodynamic Optimization of the Ternary Ga-Sn-Te System Using Modified Quasichemical Model

Thermoelectric (TE) materials are of great interest to many researchers because they directly convert electric and thermal energy in a solid state. Various materials such as chalcogenides, clathrates, skutterudites, eutectic alloys, and intermetallic alloys have been explored for TE applications. The Ga-Sn-Te system exhibits promising potential as an alternative to the lead telluride (PbTe) based alloys, which are harmful to environments because of Pb toxicity. Therefore, in this study, thermodynamic optimization and critical evaluation of binary Ga-Sn, binary Sn-Te, and ternary Ga-Sn-Te systems have been carried out over the whole composition range from room temperature to above liquidus temperature using the CALPHAD method. It is observed that Sn-Te and Ga-Te liquids show the strong negative deviation from the ideal solution behavior. In contrast, the Ga-Sn liquid solution has a positive mixing enthalpy. These different thermodynamic properties of liquid solution were explicitly described using Modified Quasichemical Model (MQM) in the pair approximation. The asymmetry of ternary liquid solution in the Ga-Sn-Te system was considered by adopting the toop-like interpolation method based on the intrinsic property of each binary. The solid phase of SnTe was optimized using Compound Energy Formalism (CEF) to explain the high temperature homogeneity range, whereas solid solution, Body-Centered Tetragonal (BCT) was optimized using a regular solution model. Thermodynamic properties and phase diagram in the Ga-Sn-Te and its sub-systems were reproduced successfully by the optimized model parameters. Using the developed database, we also suggested several ternary eutectic compositions for designing TE alloy with improved properties.

Hydrocarbon gas leakage from high‐pressure system in the Yanan Sag, Qiongdongnan Basin, South China Sea

Despite high pressure being ubiquitous in the Yanan Sag of the Qiongdongnan Basin, South China Sea, its potential effect on gas migration‐accumulation remains unclear. In this study, a series of geochemical indicators combined with the origin of high pressure were used to elucidate the cause of gas accumulation failure in the overpressured YC19‐1 structure. Drill‐stem tests, mud weights, and well‐loggings reveal two vertical overpressure systems. Pore pressure in the deep Lingshui and Yacheng formations almost reaches a lithostatic magnitude, which was interpreted as a result of gas generation and disequilibrium compaction triggered by the Pliocene‐Quaternary rapid subsidence. A thermal anomaly above the high‐pressure system was evidenced by high homogenization temperature (Th) of fluid inclusion, abnormally high vitrinite reflectance, and a rapid transformation from kaolinite to illite. The high thermal field likely resulted from a cross‐stratal fluid migration from the deep high‐pressure system. Both methane‐bearing inclusions in sandstones and abnormal Rock‐Eval data of mudstones above the high‐pressure surface suggest an influx of external hydrocarbons. Based on primary aqueous inclusion Th and salinity, carbon and oxygen isotope compositions, and petrographic observations, widespread silica and carbonate cements near the overpressure surface were interpreted to be derived from extraformational materials carried by deep‐seated basinal fluids. Fluid inclusion Th coupled with burial model suggests that the gas leakage took place at circa 1.6 Ma, coinciding well with the stages of both gas generation and overpressure. These observations suggest an upward leakage of gas‐bearing fluids induced by pressure release, thus leading to the existence of only non‐commercial gas‐bearing aquifers in the overpressured YC19‐1 structure.

Origin of Drusy Dolomite Cement in Permo-Triassic Dolostones, Northern United Arab Emirates

While the characteristics and origin of drusy calcite cement in carbonate deposits is well constrained in the literature, little attention is paid to drusy dolomite cement. Petrographic observations, stable isotopes, and fluid-inclusion microthermometry suggest that drusy dolomite cement in Permo-Triassic conglomerate/breccia dolostone beds in northern United Arab Emirates has precipitated as cement and not by dolomitization of drusy calcite cement. The low δ18OVPDB (−9.4‰ to −6.2‰) and high homogenization temperatures of fluid inclusions in drusy dolomite (Th = 73–233 °C) suggest that dolomitization was caused by hot basinal brines (salinity = 23.4 wt% NaCl eq.). The δ13CVPDB values (+0.18‰ to +1.6‰) and 87Sr/86Sr ratio (0.708106 to 0.708147) indicate that carbon and strontium were derived from the host marine Permo-Triassic carbonates. Following this dolomitization event, blocky calcite (Th = 148 °C; salinity = 20.8 wt% NaCl eq.) precipitated from the hot basinal brines. Unravelling the origin of drusy dolomite cement has important implications for accurate construction of paragenetic sequences in carbonate rocks and decipher the origin and chemistry of diagenetic waters in sedimentary basins.

Precipitation of Al3Zr by two-step homogenization and its effect on the recrystallization and mechanical property in 2195 Al–Cu–Li alloys

To improve the recrystallization resistance of 2195 Al–Cu–Li alloys, we proposed a two-step homogenization (TS) to facilitate the homogeneous nucleation of Al3Zr, and the effect of Al3Zr precipitate on the recrystallization behavior and on the strength and ductility of 2195 alloys were investigated. It is shown that the first low-temperature homogenization in TS promotes the nucleation of Al3Zr due to large driving force, and second high-temperature homogenization helps to accelerate diffusion process of Zr, resulting in fine and dense Al3Zr distribution (radius of 22.6 ± 4.1 nm and number density of 1.94 × 1020/m3). As a result, the recrystallization resistance of 2195 alloys is significantly improved comparing with those treated by the traditional one-step homogenization (OS). The TS alloys exhibits best yield strength (566.7 MPa), tensile strength (598.8 MPa) and elongation of 11.9% comparing with OS alloys. The strength improvement of TS 2195 alloys mainly originates from Orowan mechanism and grain refinement induced by Al3Zr precipitate. The remained deformed lamellar structure in TS alloys effectively deflectes and zigzags the propagation of cracks, which is beneficial to the energy dissipation, leading to the enhancement of ductility.

Influence of Fe and Mn on the Microstructure Formation in 5xxx Alloys-Part I: Evolution of Primary and Secondary Phases.

The increasing demands for Al sheets with superior mechanical properties and excellent formability require a profound knowledge of the microstructure and texture evolution in the course of their production. The present study gives a comprehensive overview on the primary- and secondary phase formation in AlMg(Mn) alloys with varying Fe and Mn additions, including variations in processing parameters such as solidification conditions, homogenization temperature, and degree of cold rolling. Higher Fe alloying levels increase the primary phase fraction and favor the needle-shaped morphology of the constituent phases. Increasing Mn additions alter both the shape and composition of the primary phase particles, but also promote the formation of dispersoids as secondary phases. The size, morphology, and composition of primary and secondary phases is further affected by the processing parameters. The average dispersoid size increases significantly with higher homogenization temperature and large primary particles tend to fragment during cold rolling. The microstructures of the final soft annealed states reflect the important effects of the primary and secondary phase particles on their evolution. The results presented in this paper regarding the relevant secondary phases provide the basis for an in-depth discussion of the mechanisms underlying the microstructure formation, such as Zener pinning, particle stimulated nucleation, and texture evolution, which is presented in Part II of this study.

Composition of ore-forming fluids in the Huangshuian carbonatite-related Mo-(REE) deposit: Insights from LA-ICP-MS analyses of fluid inclusions

The carbonatites in the southern margin of the North China Craton are distinguishable by containing abundant quartz and are closely spatially associated with Mo-(REE) deposits. Unveiling the nature of ore-forming fluids is key to understand the genesis of these Mo-(REE) deposits and to explore their potential genetic relationships with the quartz-rich carbonatites, but such issues were currently not convincingly addressed. Here, we provide detailed petrographic, microthermometric and LA-ICP-MS analyses of the fluid inclusions hosted in the primary quartz from the carbonatites in the Huangshuian Mo-(REE) deposit which is the largest Mo-(REE) one in the region, containing 0.4 million tons of Mo metal with REEs as the major by-product. Our results show that the fluid inclusions in the quartz of the carbonatites are two- and three-phase CO2-bearing types with high homogenization temperatures (average at 396 °C) and low salinities (average at 3.88 wt% NaCl equiv). The LA-ICP-MS analyses of these inclusions reveal that the primary fluids contain high concentrations of La, Ce, Pr, Nd, Sr, and Ba, similar to typical carbonatite-related fluids. In addition, they are characterized by high Y, Cu, Pb, and Zn. Such a metal association is broadly consistent with the mineral assemblages of the Huangshuian Mo-(REE) deposit, such as the widespread barite, bastnäsite, xenotime, chalcopyrite, galena, and sphalerite, strongly supporting the close genetic relation of the deposit with the quartz-rich carbonatites. Although the concentrations of Mo are extremely low in these inclusions (below the detect limit), it was constrained to be gradually enriched in evolved fluids. Considering that the recorded fluids in quartz represent earliest generation of fluids exsolved from carbonatite magmas, our new results highlight that quantifying metal budgets of fluid inclusions could be a robust way to evaluate fertility of carbonatites that are widespread in the southern margin of the North China Craton.

Fluid inclusion and C-O isotopic constrains on the origin and evolution of ore-forming fluids of the Badaguan Cu-Mo deposit, Inner Mongolia

The Badaguan porphyry Cu–Mo deposit is located in the Derbugan metallogenic belt. Aqueous (W-type), CO2-rich (WC-type), vapor-rich (V-type), and daughter mineral–bearing inclusions (S-type) were recognized in the hydrothermal quartz. Fluid inclusions in the early stage show high homogenization temperatures (247–374 ℃) and high pressures (66–191 MPa), with salinities of 0.95–12.15 wt% NaCl equiv. The presence of anhydrite in veins and phenocrysts suggests high oxygen fugacity conditions. The veins in the Mo- and Cu mineralization stages were formed by immiscible fluids at temperatures of 244–366 ℃ and 183–342 ℃, and pressures of 39–137 MPa and 30–98 MPa, respectively. They yielded salinities of 1.69–10.52 and 0.35–6.85 wt% NaCl equiv, respectively. Homogenization temperatures of fluid inclusions in late stage range from 194 to 269 ℃ with a salinity of 0.6–5.88 wt% NaCl equiv. It is concluded that the ore-forming fluids in the early stage were magmatic in origin, then gradually diluted and cooled by meteoric water. During this process, fluid immiscibility and CO2 release induced by pressure drop and oxygen fugacity decrease resulted in Mo mineralization, while temperature drop was the main trigger for the precipitation of chalcopyrite. Laser-Raman analyses suggest that the fluid inclusions of the Badaguan porphyry Cu-Mo deposit in Inner Mongolia are rich in CO2. Minor CH4 occurs in the Mo- and Cu-mineralization stage, which may be generated during water–rock interaction. The hybrid carbon isotope compositions of the fluid inclusions, mainly representing CO2, show a very depleted δ13CPDB (−21‰ to −28.3‰), which can be explained by the joint influence of ~ 0.5% subducted oceanic sedimentary contamination in the mantle and carbon isotope fractionation induced by 35–80% CO2 degassing. Petrographic observation, previous studies on the geochemical and isotopic characteristics of ore-causative rocks rule out the possibility of contamination of ascending magma with reducing wall rocks. The large variations in δ18Owater (−6.6‰ to +2.4‰) for quartz and calcite suggest the participation of meteoric water during water–rock interaction.

Minerals Filling in Anhydrite Dissolution Pores and Their Origins in the Ordovician Majiagou Formation of the Southeastern Ordos Basin, China

Mold pore cementation is the key factor constraining the reservoir property in the study area. The anhydrite dissolution pores in the Ordovician Majiagou Formation of southeastern Ordos Basin are commonly filled by minerals such as dolomite, calcite, pyrite, and quartz accounting for more than 90% of the total molds resulting in significant porosity volume reduction. The anhydrite dissolution pores in the Jingbian Gas Field in the middle east of the basin, however, are rarely filled by minerals with more than 30% molds, remaining open to become good reservoir space. Studies reveal that the calcite filling in anhydrite dissolution pores has a relatively negative δ18O value (-15.58‰~-8.96‰ VPDB) and negative δ13C value (-7.56‰~0.26‰ VPDB), which is interpreted to be caused by thermochemical sulfate reduction (TSR). The higher homogenization temperatures (140-234°C) and high salinity (19.13-23.18 wt.% NaCl equivalent) of the primary inclusions in calcite confirm the above interpretation. Dolomite is the second most abundant carbonate formed as by-product of TSR, which is promoted by the precipitation of calcite and resulted enriched in Mg2+/Ca2+ ratio in the pore water. Pyrite forms by the reaction of H2S released from TSR with the Fe2+ in the horizon, which is supported by its cubic habit and relatively high δ34S value (10.50‰~24.00‰VCDT). Quartz with relatively high homogenization temperature (113-154°C) is considered to precipitate in low-pH solution from calcite and pyrite precipitation after TSR. The southeastern Ordos Basin is much lower than the Jingbian Gas Field in paleogeographic location, which is submerged in the sea water of marine phreatic environments for a long time when sea water flooded from the southeastern direction. TSR occurs due to calcium sulfate enriched in pore water resulting in the minerals of dolomite, calcite, pyrite, and quartz filling in the molds leading to the low porosity and permeability of the study area.

Fluid inclusion evidence for hydrothermal evolution of the Sadaigoumen porphyry Mo deposit on the northern margin of the north China Craton

The Sadaigoumen porphyry Mo deposit is located on the northern margin of the North China Craton (NCC). In this study, in situ fluid-inclusion analyses including microthermometry, laser Raman spectroscopy, and LA–ICP–MS microanalysis, as well as Quartz H–O isotopes are present to precisely constrain the hydrothermal evolution of the Sadaigoumen deposit. Five stages of hydrothermal activity are identified, with Stage 1 characterized by the development of magnetite with rare sulfide minerals; Stage 2 by K-feldspar as the typical vein mineral; Stage 3 by molybdenite mainly in veins; Stage 4 by the development of fluorite–quartz and quartz–pyrite veins; and Stage 5 by barren carbonate–quartz veins. Fluid inclusion types were distinguished based on petrographic observations and microthermometric analysis, and fluid compositions were detected by LA–ICP–MS. Microthermometric analyses indicate decreasing homogenization temperatures in primary fluid inclusions from Stage 1 to Stage 3. Intermediate-density fluids of stages 1 and 2 are characterized by high homogenization temperatures (420 °C–470 °C), moderate salinities (6.3–11.2 wt%), and high Mo contents (52–541 ppm). Hydrothermal evolution during Mo mineralization in Stage 3 is characterized by immiscible inclusion assemblages that formed through phase separation from intermediate-density fluid. Fluid inclusions of Stage 3 were trapped at pressures fluctuating around the two-phase fluid surface, leading to at least two fluid immiscible phases (373 °C–414 °C and 311 °C–341 °C). The Mo contents of fluid inclusions vary greatly in Stage 3, with Mo tending to be enriched in brine. In stages 4 and 5, fluids display characteristics that indicate mixing with meteoric water, with homogenization temperatures (<299 °C) and salinities (<5.8 wt%) decreasing together with Mo content. The Cs/(Na + K + Mn + Fe) ratios of fluid inclusions are stable from stages 1 to 4, indicating a constant supply of ore-forming fluids from an underlying, geochemically uniform magma chamber. The fluid inclusion data suggest that Mo and Cu in the initial exsolved fluids of the Sadaigoumen porphyry Mo deposit display different migration and precipitation progresses, which is of great significance to the study of the delicate ore-forming progress of porphyry Mo (–Cu) deposits in the northern NCC.