Spinel Inclusions Research Articles

Textural and chemical variations in peridotite induced by hydrous melt migration in mantle under the back-arc spreading

This study presents the structural and petrological characteristics of mantle peridotites in relation to the rock-hydrous melt reaction found in the Hayachine ultramafic complex, NE Japan. We conducted sampling, microstructural observations, crystal-orientation analyses, and major element composition analyses of the major constituent minerals in the peridotites. We used 17 serpentinized peridotites that preserved better mantle textures. The peridotites are composed of lherzolite to harzburgite, consisting of olivine, orthopyroxene, clinopyroxene, amphibole, and spinel. The peridotites were classified into two textures according to olivine grain size: coarse-grained (ca. 2–3 mm) and fine-grained (ca. 0.3–0.5 mm). Fine-grained peridotites were newly found in this study and were characterized by aggregates of orthopyroxene and amphibole with a large number of spinel inclusions. Based on olivine crystal-preferred orientation (CPO), we found that the coarse-grained peridotites were further classified into Group 1 (A type CPO) and 2 (AG type CPO) and the fine-grained peridotites were accordingly classified into Group 3 (weak CPO). The systematic continuity in the chemical compositions of the minerals suggests that Group 1 peridotites partially melted to form Group 2 peridotites, followed by Group 3 peridotites, due to further reaction of Group 2 peridotites with hydrous melts. These textural and chemical variations in the peridotites could have resulted from rock-hydrous melt reactions under back-arc spreading and subsequent processes.

Three-Dimensional Imaging of Non-metallic Inclusions in Steel Using Ionoluminescence

Obtaining information on the morphology, size, distribution, and chemical composition of non-metallic inclusions in steel helps control the steel production process and the quality of the steel products. Two-dimensional analysis is commonly used to acquire this information; however, more accurate data can be obtained through three-dimensional analysis, leading to a better control of the quality of steel products and their production process. Currently, several techniques are proposed for the three-dimensional analysis of non-metallic inclusions; however, they are time consuming. Herein, the author presented a method to rapidly obtain three-dimensional images of non-metallic inclusions in steel using ionoluminescence (IL). A three-dimensional image of MgO·Al2O3 spinel inclusions was constructed based on two-dimensional IL images obtained every 10 min during argon–ion bombardment. The proposed IL imaging can cover an oval-shaped area of 1.17 mm × 0.26 mm on the semi-major and in the semi-minor axes, respectively, at a single measurement. Three-dimension images of MgO·Al2O3 spinel inclusions with sizes more than 20 μm can be obtained within 4 hours. Therefore, the IL imaging proposed here can provide a precise and rapid account of the effects of non-metallic inclusions on steel products and the steel production process.

Melt inclusions in spinel from a composite mantle xenolith

Composite mantle xenoliths from the Cima Volcanic Field (CA, USA) contain a variety of melt (now glassy) inclusions hosted within mantle phases. The compositions and textures of these melt inclusions have the potential to constrain their trapping processes, melt sources, and the rates of ascent of their parent xenoliths. Here we focus on unusual spinel-hosted melt inclusions from one composite xenolith, reporting glass and daughter mineral compositions and textures and attempting to reconstruct inclusion bulk compositions. The xenolith contains spinel-hosted melt inclusions in its harzburgite, olivine-websterite and lherzolite layers; there are none in its orthopyroxenite layer.The glass compositions and reconstructed bulk compositions of the partly-crystallized inclusions correspond to alkaline intermediate melts, mostly trachyandesites. Such melts are most likely to be generated and trapped by vapor-undersaturated phlogopite or amphibole dehydration melting to an assemblage of liquid + spinel + olivine ± pyroxenes. We modeled the near-liquidus phase relations of the inclusion bulk compositions and noted the closest approach of each inclusion to simultaneous saturation with spinel and either phlogopite or amphibole, resulting in estimated trapping pressures of ∼0.5–1.5 GPa and temperatures of ∼1000–1100 °C. The large size of the hosting spinel grains suggests a slow process associated with these breakdown reactions, probably thinning of the lithosphere and steepening of the geotherm during regional extension.A linear correlation between the vesicle area and inclusion area (as proxies for volume) suggests an in-situ exsolution process from melts of relatively uniform volatile initial contents, consistent with trapping of vapor-undersaturated melts that later exsolve vapor during cooling and daughter crystal growth. A negative correlation between the glass content in melt inclusions and the size of the inclusion itself suggests a control on the degree of crystallinity with the size. There appears to be a two-stage cooling history captured by the inclusions, forming first prismatic daughter crystals and large round vesicles at the wall of the inclusion, followed by quenching to form a mat of fine crystallites and small vesicles in most inclusions. We connect the final quench to rapid ascent of the xenolith in its host melt, which also triggered partial breakdown of remaining amphibole to fine glassy symplectites.

The Effect of Ca Pretreatment on the Characteristics of Rare‐Earth Nonmetallic Inclusions in Super‐Duplex Stainless Steel

Rare‐earth treatment enhances steel properties. Nevertheless, this beneficial effect can be counterbalanced by the formation of large‐sized rare‐earth inclusions. To refine and spheroidize these inclusions, Ca pretreatment is employed between Al deoxidation and Ce treatment stages for super‐duplex stainless steel 2507 at 1580 °C, using a vertical tube furnace. A systematic analysis is performed to compare the characteristics of nonmetallic inclusions between the Ca‐untreated and Ca‐treated tests. Prior to Ce addition, Ca pretreatment transforms irregular and clustered MgO–Al2O3 spinel inclusions into spherical CaO–MgO–Al2O3 inclusions. Additionally, Ca pretreatment significantly reduces mean diameter of the inclusions from 2.36 ± 0.54 to 1.27 ± 0.47 μm. After Ce addition, rare‐earth inclusions appear near‐spherical with few clustered inclusions in Ca pretreatment case. Conversely, the absence of Ca treatment results in numerous clustered inclusions, thereby yielding significantly larger rare‐earth inclusions, measuring 2.75 ± 1.66 μm compared to 1.99 ± 1.09 μm. CaO component in CaO–MgO–Al2O3 inclusions is largely reduced by Ce. Consequently, Ca pretreatment only yields slight alterations in chemical composition of rare‐earth inclusions. Ce in situ reduces parent inclusions, initiating from the periphery and progressing toward the center. Therefore, the size and morphology of final rare‐earth inclusions are largely inherited from parent inclusions.

Study on the Causes and Control Measures of Mg–Al Spinel Inclusions in U75V Heavy Rail Steel

U75V heavy rail steel production uses an aluminum-free deoxidation process; however, large particles of MgO–Al2O3 inclusions form in the steel, which has a great impact on product quality. In this paper, we try to explain how spinel inclusions, which affect the metallurgical quality of heavy rail steel, are produced by thermodynamic and experimental methods, and then determined measures for avoiding such inclusions. The formation mechanism of spinel inclusions in U75V heavy rail steel was determined through the analysis of nozzle clogging in the pouring process and typical inclusions in steel. The results show that there are two types of spinel inclusions in heavy rail steel: one is pure Mg–Al spinel inclusions and the other is Mg–Al spinel inclusions coated with calcium aluminate. The small, pure Mg–Al spinel inclusions were precipitated during the solidification of the molten steel, and the precipitation temperature was related to the composition of the molten steel. The large spinel inclusions were derived from clogging of the submersed nozzle. Mg–Al spinel inclusions coated with calcium aluminate were transformed from CaO–SiO2–Al2O3–MgO complex inclusions in the steel during cooling, and the formation temperature was related to the content of Al2O3 and MgO in the inclusions. The content of Al2O3 and MgO in the inclusions was the key to the formation of the Mg–Al spinel inclusions. Therefore, in order to control the production of spinel inclusions in steel, it is necessary to strictly control the content of impurity elements such as magnesium and aluminum in the alloy auxiliary materials, to reduce the secondary oxidation of liquid steel and to reduce the erosion of refractory materials.

Metamorphic P-T-t evolution of ultrahigh-temperature granulite facies metapelites from the Lundazi terrane, Irumide Belt, Eastern Zambia

The Lundazi terrane is part of the Mesoproterozoic Irumide Belt of Central Africa which together with other terranes of similar ages are interpreted to record collisional events relation to the amalgamation of the Rodinia Supercontinent. Pelitic granulites from the area preserve evidence of ultrahigh-temperature metamorphism and partial melting with complex textures involving garnet + sillimanite + spinel + quartz ± cordierite ± orthopyroxene, rare corundum, and ternary feldspars. Garnet porphyroblasts preserve inclusions of spinel + quartz and sillimanite + feldspar which indicate high temperatures were reached during the metamorphic peak. The metamorphic evolution of these rocks has been investigated using phase equilibria modelling and complemented by ternary feldspar thermometry and garnet-orthopyroxene thermobarometry which indicate peak conditions of up to ∼900–1000 °C and 6–9.5 kbar. The preservation of peak assemblages and textural features of these rocks suggest substantial melt loss during their prograde evolution. Melt-reintegrated pseudosections indicate isobaric heating prior to exhumation and subsequent cooling. Monazite EPMA dating identifies the thermal peak occurred at 1056–1028 ± 8 Ma, followed by retrograde recrystallization at 1003 ± 8–975 ± 7 Ma. The high-grade metamorphism is interpreted in terms of clockwise P-T-t paths with retrograde recrystallization marked by the partial resorption of garnet rims to form plagioclase, the growth of late cordierite around garnet and sillimanite, and alteration of monazite. The absence of a Neoproterozoic overprint in the area indicates the Lundazi terrane is part of the Irumide Belt s.s rather than the Southern Irumide Belt, and a revision of the boundary between the two regions is proposed.

Effect of α-Al2O3 content on microstructures, mechanical properties and purification efficiency on molten steel of MgO-based filters

In this study, five sets of MgO-based ceramic filters were prepared using porous MgO powder and α-Al2O3 micro-powder as raw materials. The effect of α-Al2O3 content on the microstructures, mechanical properties and purification efficiency of MgO-based filters were investigated via SEM, EDS, and immersion test in molten steel, etc. The results indicate that the reactive sintering between α-Al2O3 and MgO promoted the formation and growth of neck connections of magnesium aluminate spinel between grains, increased the density of the filter skeleton, and decreased the pore size inside the skeleton. The higher density and smaller pore size of the skeleton, as well as the neck connection of spinel and crack deflection effect caused by magnesium aluminate spinel, comprehensively improved the strength and thermal shock resistance of MgO-based ceramic filters. Furthermore, the results from the immersion test in molten steel revealed that an appropriate amount of high-temperature liquid phase, smaller pore size, and in-situ generated spinel were beneficial for the filters to adsorb dissolved aluminum, dissolved oxygen, alumina inclusions, and secondary spinel inclusions in the steel. The filter with 20 wt.% α-Al2O3 had the best overall performance with a compressive strength of 2.35 MPa, a compressive strength after thermal shock test of 1.91 MPa and an efficiency of 77.3% in reducing the total oxygen content of the steel.

COMPOSITION OF PHENOCRYSTS OF LAMPROITE LAVA, GAUSSBERG VOLCANO, EAST ANTARCTICA

This paper presents numerous new data on the geochemical composition of olivine, clinopyroxene, and leucite phenocrysts, as well as spinel inclusions in olivine and quench glass from lamproites of the Gaussberg Volcano (East Antarctica). Most of the olivine phenocrysts in the Gaussberg lamproites are high Mg varieties (Fo 89–91) with elevated Ni contents (up to 4900 ppm) and high Ni/Co ratios. According to the data of about 320 analyzes of clinopyroxenes, two groups of phenocrysts belonging to the diopside group have been established. Group I consists mainly of high-Mg varieties (Mg#80), while group II clinopyroxenes are less magnesian (Mg# 52–80). The main difference between the clinopyroxenes of the two groups is manifested in the increased contents of Al2O3, FeO and reduced TiO2, Cr2O3, and NiO in the compositions of group II compared to group I, as well as different contents of trace elements, which may reflect their crystallization from different types of primary melts. According to the study of about 550 grains of leucite phenocrysts in Gaussberg lamproites, it was shown that they correspond to the ideal stoichiometry of leucite K[AlSi2O6] and are enriched in Na2O (0.05–0.35 wt %), but depleted in K2O (19.9–20.9 wt %) compared to with leucites from lamproites of other provinces. The BaO content reaches 0.3 wt %. %, SrO –0.04 wt. %. The iron content in most leucite phenocrysts varies within 0.7–1.2 wt % Fe2O3, with individual grains with low Fe2O3 contents (0.5 wt %). In microlites of leucite in the groundmass and rims of phenocrysts, the iron content can reach 2.4 wt % Fe2O3, which may indicate more oxidized conditions at the time of lava eruption.Based on the study of natural samples, existing experimental data and computational models, the order and conditions of crystallization of Gaussberg lamproites were restored. Crystallization proceeded in the following order: chrome spinel - chrome spinel + olivine - olivine + leucite (± chrome spinel) - olivine + leucite + clinopyroxene (± chrome spinel). The near-liquidus association, represented by high-Mg olivine phenocrysts with inclusions of Cr-spinel, was formed in the temperature range from 1180 to 1250°C. Further crystallization of the melt with the formation of an association of olivine+leucite+clinopyroxene phenocrysts could occur at pressures below 2 GPa and temperatures of 1070–1180°C, corresponding to the presence of water in the magmatic system. Estimates of the redox conditions of crystallization of lamproites, obtained using different oxybarometers, vary in a wide range from QFM-0.5 to QFM+2.3.Elevated Ni contents in liquidus olivines of Gaussberg indicate high nickel contents in the source. It is shown that the possible formation of ultraalkaline magmas in the region of Gaussberg Volcano occurred during the melting of the continental lithosphere, which was heterogeneous and included both the peridotite mantle and hydrous pyroxenite fragments.

Composition of Phenocrysts in Lamproites of Gaussberg Volcano, East Antarctica

—This paper presents numerous new data on the geochemical composition of olivine, clinopyroxene, and leucite phenocrysts, as well as spinel inclusions in olivine and quench glass from lamproites of Gaussberg volcano (East Antarctica). Most of the olivine phenocrysts in the Gaussberg lamproites are high Mg varieties (Fo89–91) with elevated Ni contents (up to 4900 ppm) and high Ni/Co ratios. According to data of about 320 clinopyroxene analyses, two groups of diopsidic phenocrysts have been established. Group I consists mainly of high-Mg varieties (Mg#>80), while group II clinopyroxenes are less magnesian (Mg# 52–80). The main difference between the clinopyroxenes of the two groups is the elevated contents of Al2O3, FeO and reduced TiO2, Cr2O3, and NiO in the compositions of group II compared to group I, as well as different contents of trace elements, which may reflect their crystallization from different types of primary melts. According to the study of ~550 grains of leucite phenocrysts in the Gaussberg lamproites, it was shown that they correspond to the ideal stoichiometry of leucite K[AlSi2O6] and are enriched in Na2O (0.05–0.35 wt %), but depleted in K2O (19.9–20.9 wt %) compared to leucites from lamproites of other provinces. The BaO content reaches 0.3 wt %, SrO –0.04 wt %. The iron content in most leucite phenocrysts varies within 0.7–1.2 wt % Fe2O3, but some grains have the low Fe2O3 contents (<0.5 wt %). In leucite microlites of the groundmass and rims of phenocrysts, the Fe2O3 content can reach 2.4 wt %, which may indicate more oxidized conditions at lava eruption. Based on the study of natural samples, existing experimental data and numerical models, the order and conditions of crystallization of the Gaussberg lamproites were obtained. Crystallization proceeded in the following order: chromian spinel → chromian spinel + olivine → olivine + leucite (± chromian spinel) → olivine + leucite + clinopyroxene (± chromian spinel). The near-liquidus assemblage represented by high-Mg olivine phenocrysts with inclusions of Cr-spinel was formed in the temperature range from 1180 to 1250°C. Further crystallization of the melt with the formation of an association of olivine+leucite+clinopyroxene phenocrysts could occur at pressures below 2 GPa and temperatures of 1070–1180°C, corresponding to the presence of water in the magmatic system. Estimates of the redox conditions of crystallization of lamproites obtained using different oxybarometers vary in a wide range from QFM-0.5 to QFM+2.3. The elevated Ni contents in liquidus olivines of Gaussberg indicate the high nickel contents in the source. It is shown that the formation of ultra-alkaline magmas in the Gaussberg volcano area is likely related to melting of the continental lithosphere, which was heterogeneous and included both the peridotite mantle and hydrous pyroxenite fragments.

First measurements of the Fe oxidation state of spinel inclusions in olivine single crystals from Vulture (Italy) with the in situ synchrotron micro-Mössbauer technique

Abstract. The redox state of the Earth's upper mantle (i.e., oxygen fugacity, fO2) is a key variable that influences numerous processes occurring at depth like the mobility of volatile species, partial melting, and metasomatism. It is linked to the oxidation state of peridotite rocks, which is normally determined through the available oxythermobarometers after measuring the chemical composition of equilibrated rock-forming minerals and the Fe3+ in redox-sensitive minerals like spinel or garnet. To date, accurate measurements of Fe3+ / ∑Fe in peridotites have been limited to those peridotites (e.g., harzburgites and lherzolites) for which an oxythermobarometer exists and where spinel (or garnet) crystals can be easily separated and measured by conventional 57Fe Mössbauer spectroscopy. Wehrlitic rocks have been generally formed by the interaction of a lherzolite with carbonatitic melts and, therefore, have recorded the passage of (metasomatic) fluids at mantle conditions. However, no oxythermobarometer exists to determine their equilibrium fO2. The aim of this study was to retrieve the fO2 of the mantle beneath Mt. Vulture volcano (Italy) through the study of a wehrlitic lapillus emitted during the last eruption (∼ 140 kyr ago) that contain olivines with multiple tiny spinel inclusions with sizes &lt; 40 µm. To our knowledge, the Fe oxidation state of these inclusions has been never determined with the Mössbauer technique due to their small sizes. Here, we present measurements of the Fe3+ / ∑Fe using in situ synchrotron Mössbauer spectroscopy coupled with chemical and spectroscopic analysis of both host olivine and spinel inclusions. The results show Fe3+ / ∑Fe ratios of 0.03–0.05 for olivine and 0.40–0.45 for the included spinels, the latter of which appear higher than those reported in literature for mantle spinel harzburgites and lherzolites. Given the evidence of the mantle origin of the trapped spinels, we propose that the high fO2 (between 0.81 and 1.00 log above the fayalite–magnetite–quartz buffer; FMQ) likely results from the interaction between the pristine spinel lherzolite and a CO2-rich metasomatic agent prior to the spinel entrapment in olivines at mantle depths.

Effect of ferrochromium (FeCr) and ferroniobium (FeNb) alloys on inclusion and precipitate characteristics in austenitic stainless steels

Lab-scale alloying experiments were carried out by first adding commercial low-carbon ferrochrome (LCFeCr) alloys and then adding ferroniobium (FeNb) alloys in 316-grade austenitic stainless steel in this study. The inclusion and precipitation characteristics in LCFeCr and FeNb were evaluated as well as in a 316 austenitic stainless steel after the alloy additions by using two- and three-dimensional characterization methods in combination with thermodynamic calculations. The results showed that MnCr2O4 spinels and pure Al2O3 were the main types of inclusions in LCFeCr alloys, while pure TiOx, Al2O3 inclusions and complex TiOx-Al2O3 aggregates were mainly found in FeNb alloys. After the addition of LCFeCr alloy to the steel, the SiO2 contents in liquid inclusions decreased to some extent, while more inclusions containing higher MnO contents were observed. Some MnCr2O4 spinel inclusions can be reduced by Si in steel and form liquid inclusions. Some MnCr2O4 spinel and Al2O3 inclusions from LCFeCr alloy can remain in the steel melt, which decreased the steel cleanliness. After the addition of FeNb alloy, pure TiOx inclusions present in this alloy can hardly be found in the steel melt. The inclusion types in steel were not changed so much but high Nb-containing phases were found around the inclusions and coarse Laves phases were formed in the matrix. Overall, this work aims to understand the impurity particle behavior during the alloying process when using ferroalloys to produce high-performance stainless steels.

Thermodynamic Formation and Three-dimensional Characterization of MnS–MgAl&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;4&lt;/sub&gt; Composite Inclusions in Steel

The distribution and morphology of inclusions in steel have an important effect on the quality of steel. It has been proved that the oxide inclusions can be modified into small and dispersed spinel inclusions by adding proper amount of Mg in steel. The MnS-MgAl2O4 composite inclusions are formed with the core of MgAl2O4 inclusions during the solidification process of molten steel, which has deforming ability and can improve the properties of materials steel. However, the investigation of the control of the composite inclusions is limited by the lack of understanding structure of the inclusions. In this study, the Mg treated steel samples were prepared by induction furnace in this study. In the experiment, SEM-EDS was used to characterize the samples, and thermodynamic calculations were used to describe the evolution mechanism of inclusions and MnS-MgAl2O4 composite inclusions formed in steel samples with different Mg contents. The atomic mismatch calculated between MnS and MgAl2O4 proves that they can nucleate effectively. The three-dimensional (3D) morphology of the composite inclusion of MnS-MgAl2O4 in steel samples were observed by using the X-ray Micro-CT in the beamline of BL16U2 at Shanghai Synchrotron Radiation Facility (SSRF). It is proved that MnS and MgAl2O4 phases exist in the form of co-associated, which is valuable for the control of composite inclusions in steel. The current work provide a powerful method to analyze the detailed structure of the composite inclusions in the steel.

Effect of Cerium on Inclusion Modification in a Secondary-Hardening Steel.

Owing to the continuous increasing of steel strength, mechanical properties including toughness and fatigue performance are becoming increasingly sensitive to inclusions in ultra-high strength steel. Rare-earth treatment is considered as an effective method to reduce the harmful effects of inclusions, but is rarely applied in secondary-hardening steel. In the present study, different amounts of cerium were added in a secondary-hardening steel to investigate the modification effect of Ce on non-metallic inclusions in steel. The characteristics of inclusions were observed experimentally using SEM-EDS and the modification mechanism was analyzed based on thermodynamic calculations. The results indicated that the main inclusions in Ce-free steel are Mg-Al-O + MgS. Thermodynamic calculation indicated that MgAl2O4 is firstly formed in liquid steel and then successively transformed into MgO and MgS during cooling process. When the Ce content is 0.0030%, the typical inclusions in steel were individual Ce2O2S and MgO + Ce2O2S complex inclusions. When the Ce content was increased to 0.0071%, the typical inclusions in steel were individual Ce2O2S- and Mg-containing inclusions. Ce treatment modifies the angular magnesium aluminum spinel inclusions into spherical and ellipsoidal Ce-containing inclusions, thus reducing the harmful effect of inclusion on steel properties.

Effect of Manufacturing Conditions and Al Addition on Inclusion Characteristics in Co-Based Dual-Phase High Entropy Alloy

Three Co-based dual-phase high-entropy alloys (HEAs) were produced by different manufacturing conditions: arc-melting with Ar protection (Ar-HEA), vacuum induction melting in Al2O3 crucible (Cr-HEA) and vacuum induction melting with 0.5 at. pct Al (Al-HEA), which resulted in different levels of impurity elements and inclusion characteristics. The inclusions that precipitated in different HEA samples were investigated through an electrolytic extraction process and scanning electron microscopy-energy dispersive spectroscopy (SEM-EDS) characterization. The results showed that Mn(S,Se) inclusions were presented in all three alloys. MnCr2O4 inclusions were presented only in Ar-HEA, pure Al2O3 inclusions were presented in Cr-HEA and Al-HEA, and Mn–Cr–Al–O inclusions were also found in Al-HEA. Thermodynamic calculation software FactSage and Thermo-calc were used to predict the inclusion formations of the HEAs, which showed a good agreement with the experimental findings. The stable inclusions can transform from MnCr2O4 to Mn(Cr,Al)2O4 and then to pure Al2O3 with the increase of Al content. The inclusions in Al-containing HEA are spinel or Al2O3 depending on the content levels of Al and O. It is proposed that the formation of spinel and Al2O3 inclusions can be avoided in liquid HEA when the O content is controlled to be very low, which can result in smaller-sized inclusions. Moreover, the calculated coagulation coefficient of spinel inclusions is close but lower than that of Al2O3 inclusions. The collision growth of inclusions was affected by a combination of physical parameters of HEA and inclusions as well as the inclusion size and amount.Graphical

Influence of Mg on Inclusions in 21-4N Valve Steel

In order to explore the influence of different magnesium contents on the morphology, size, distribution and composition of inclusions in 21-4N austenitic valve steel, the inclusions in 21-4N austenitic valve steel with different magnesium contents smelted by high temperature resistance furnace were analyzed by Zeiss metallographic microscope and scanning electron microscope. The results show that the average yield of magnesium in steel is only 4.50% due to the high vapor pressure of magnesium in the laboratory smelting process. When the mass fraction of magnesium is 0-60ppm, with the increase of magnesium content, the main inclusions in steel mostly change from the initial Al2O3 and Al-Mn-O inclusions to Al-Mg-O spinel inclusions and Al-Mg-O composite inclusions. With the further addition of Mg, a large number of large-size MgO inclusions began to appear in steel. The average size of inclusions in 21-4N steel decreased from 4.576μm to 2.89μm, and the density of inclusions increased from 54 to 132 /mm2. The distribution uniformity of inclusions is obviously improved.

Specific features of the microimpurity composition of chrome-spinel inclusions in diamonds from kimberlites of Sakha-Yakutia

Specific features of the microimpurity composition of chrome-spinel inclusions in 323 diamond crystals from eight kimberlite pipes of two diamond-bearing regions of Yakutia were revealed by microprobe analysis. Processed data on their content of the Ni, Zn, V, Mn, and Si impurities are presented. It is shown that chrome-spinels in diamonds from the kimberlite pipes of the different regions are characterized by different contents of the impurity elements. The revealed differences in the composition of chrome spinel inclusions in the diamonds, as well as in the defect-impurity composition of the hosting diamonds, from the different, including neighboring, kimberlite pipes of Yakutia, are evidence of a local heterogeneity in the mantle composition within a certain kimberlite field. These data confirm the opinion of most researchers on heterogeneity of the mantle composition in different regions of the Yakutian diamondiferous province.

The effect of Ce addition on purification and inclusion modification of CoCrFeNiMn high entropy alloy

This study focuses on purification and inclusion modification mechanism of equiatomic CoCrFeNiMn high entropy alloys with addition of various cerium (within the range of 0–0.0445 %) smelted by Vacuum Arc Melting (VAM), It was found that there are three types of inclusions in CoCrFeNiMn alloys: Mn(S, Se), AB2O4 spinel type, mixed type (Mn(S, Se) wraps AB2O4), and the average size of the three types of inclusions are 1.1 µm, 5.6 µm, and 4.8 µm, respectively. The addition of cerium can significantly reduce the oxygen content, as well as the sulfur content and selenium content are declined, the inclusions are refined and spheroidized simultaneously. The oxygen content, sulfur content and selenium content were reduced from 150 ppm, 46 ppm, and 105 ppm to 5–7 ppm, 22 ppm, and 80 ppm, respectively. When the cerium content is 0.0012 %, some of the inclusions are modified into three types of inclusions: Mn(S, Se) + Ce2O3, Mn(S, Se) + CeCrO3 and Mn(S, Se) + Ce2O3 + CeCrO3, while the average size of some unmodified AB2O4 spinel inclusions was reduced to 3.1 µm, and the average size of mixed inclusions was dropped to 2.6 µm. When the cerium content is 0.019 %, the inclusions in the alloy are completely modified into Ce2O2(S, Se) + Ce2(S, Se)3. Furthermore, the number density and area fraction of the inclusions are descended from 216.92 mm−2 and 0.1150 % of no cerium alloys to 121.64 mm−2 and 0.0602 %, the inclusions are well spheroidized, and the average size of cerium inclusions is 2.2 µm. Finally, the mechanism on the modification by cerium was discussed based on the composition evolution of inclusion during solidification with Factsage calculation and experimental results. The compositions of inclusions were also analyzed based on the inclusion evolution model.

A petrologic and microstructural study of a compact type A calcium‐aluminum‐rich inclusion from the Northwest Africa 5028 CR2 chondrite: Implications for nebular and parent‐body processes

AbstractCompact type A calcium‐aluminum‐rich inclusions (CTA CAIs) are believed to have experienced partial melting that erased all information on their original nebular condensation. To investigate this question, we report new microstructural data on a CTA CAI, composed primarily of melilite, spinel, and perovskite, in the Northwest Africa 5028 CR2 chondrite. The melilite grains contain low (5–10 mole%) åkermanite contents and are not compositionally zoned. Spinel and perovskite each occur as near endmember compositions MgAl2O4 and CaTiO3 and contain minor V and Al, respectively. A continuous rim composed of melilite, spinel, and perovskite, with minor hibonite grains occur around the CAI. We extracted two regions of interest from the interior CAI and two from the rim using focused ion beam techniques for detailed analysis using transmission electron microscopy. Evidence for thermal processing occurs as a perovskite–spinel–spinel triple junction in an interior section and a spinel inclusion within perovskite in a rim section. Evidence for parent‐body alteration occurs in the form of Fe‐rich sheet silicates in the rim, and localized amstallite in the interior of the CAI. While previous work suggested that many CTA CAIs experienced thermal processing in the solar nebula, including partial melting, our data show that signatures of primary condensation can be preserved in the form of more refractory phases contained within less refractory minerals, namely melilite and perovskite grains within spinel, and hibonite grains within perovskite, respectively. The inclusion we report on here has a complex history involving gas‐phase condensation, nebular thermal processing, and parent‐body alteration.

Erosion behavior of CMAS/VA infiltrated EB-PVD Gd2Zr2O7 TBCs: Special emphasis on the effect of mechanical properties of the reaction products

Aero-engines operating in sand-laden (CMAS/CaO–MgO–Al2O3–SiO2) environments often encounter severe problems with thermal barrier coatings (TBCs) due to CMAS infiltration and erosion damage. This study focuses on a deeper understanding of the erosion behavior of CMAS-infiltrated EB-PVD Gd2Zr2O7 TBCs. The study includes isothermal infiltration of different CMAS and subsequent erosion tests at room temperature.In addition to the erosion behavior of the entire coating, the influence of different reaction products within the reaction layer on erosion failure was investigated by measuring the hardness and Young's modulus of the individual phases using in-situ REM-Nanoindentation. It was found that a garnet layer above the reaction layer and spinel inclusions within a thick apatite/fluorite reaction layer, can improve the erosion resistance of this reaction layer by 30–40%. Furthermore, a correlation between the erosion behavior and the hardness vs. Young's modulus relation, obtained from nanoindentation over the entire coating, was observed for a consistent microstructure.

Physicochemical Parameters of Ultrabasic Magmatic Systems of the Northeastern Siberian Platform (Data on Melt Inclusions in Chromian Spinel)

Abstract —Experimental studies and analysis of silicate inclusions testify to the magmatic genesis of part of chromian spinel from the Triassic deposits of the northeastern Siberian Platform. The compositions of melt inclusions in the chromian spinel show the participation of alkaline (potassic) magmas in their crystallization. Most data indicate the presence of magmatic systems similar to melts in the Guli ultrabasic massif in the northern Siberian Platform. Studies of the distribution of trace and rare-earth elements in the melt inclusions show the existence of several magmatic systems. These are, first of all, magmas that formed Guli-type ultrabasic massifs and gave rise to meimechites and picrites in the Maimecha–Kotui province. There are also plume-related magmatic systems with kimberlites, lamprophyres, and/or other continental “hot spots”. The composition of the melt inclusions suggests the existence of several types of the primary sources of chromian spinel in the northeastern Siberian Platform, which confirms the earlier data on the heterogeneous composition of the deposits of the diamondiferous Carnian (Upper Triassic) Stage. Applying computer modeling with the well-known COMAGMAT, PETROLOG, and WinPLtb programs as well as the Ol–Sp geothermometers based on the melt inclusions in chromian spinel from the Triassic deposits of the northeastern Siberian Platform, we have determined the P–T conditions of crystallization of minerals in the igneous rocks being the sources of the examined chromites. The temperature of liquidus crystallization of chromian spinel is 1324–1275 ºC. The P–T conditions of formation of olivine and clinopyroxene inclusions in it are estimated at ca. 4.5–4.1 kbar, 1510–1150 ºC and 3.2–1.0 kbar, 1285–1200 ºC, respectively.