Melt Depth Research Articles

Geochemistry and petrogenesis of the Tsirub nephelinite intrusions, southern Namibia

Field studies and geochemical analysis of a nephelinite dyke and two plug-like bodies - Tsirub (south) and Tsirub (north), occurring in southern Namibia are reported. Bulk rock geochemical analyses show that the nephelinites have limited but significant compositional variation (MgO = 8.7–12.1 wt%; Mg# = 0.61–0.71; Zr = 415–525 ppm; Nb = 152–267 ppm; Ni = 105–305 ppm; Zr/Nb = 1.8–3.1; La/Smn = 3.8–6.1). In detail, systematic minor variations in incompatible trace element abundances and ratios and Sr and Nd isotope compositions (87Sr/86Sr = 0.70335–0.70441; 143Nd/144Nd = 0.51278–0.51272) are best accounted for by small differences in degree of partial melting and some source heterogeneity. Quantitative modelling of partial melting processes indicates that compositional variations can be accounted for by low but variable degrees of partial melting (2–6%) of a peridotitic mantle. Negative K and to a lesser extent Ti, anomalies on primitive mantle normalised diagrams require melting to have occurred in the presence of minor amphibole, constraining the depth of melting to less than ~38 kbar, i.e. within the subcontinental lithospheric mantle. Heat required to raise the ambient geotherm (to ~55 mWm−2) to allow low degrees of melting of a volatile-rich (H2O–CO2 undersaturated) peridotitic lithospheric mantle is attributed to the passage of the African plate over the Vema mantle plume at 40–50 Ma. The close spatial proximity of the Tsirub nephelinite to the Dicker Willem carbonatite, Schwarzeberg nephelinite and alkaline intrusive rocks associated with the Klinghardt phonolites is taken to indicate a similar emplacement age of ~30–50 Ma and a related cause of magmatism.

The influence of process parameters on the depth of substrate melting in the technology of laser metal deposition

The dependences of the depth and width of the melt zone of the substrate on the scanning velocity, the distance from the nozzle to the substrate and the shift of the laser beam focus at different mass flow of powder in process of the track formation are obtained in the laser deposition technology using the 400 W laser with wavelength of 1.07 µm. It is shown that the width of the melt zone of the stainless substrate weakly depends on the focus shift and scanning velocity at the mass flow rate of less than 12 g/min. It narrows with increasing velocity at mass flow rate above 12 g/min. The depth of the melt zone increases with increasing intensity of the laser beam and decreases with growing mass flow. The depth is weakly dependent on the scanning velocity at flow rate of less than 15 g/min and decreases at a flow rate of more than 15 g/min with growing the scanning velocity under the condition of constancy of the radiation intensity. The obtained results allow to establish optimal values of technological parameters.

Computational Investigation of Melt Pool Process Dynamics and Pore Formation in Laser Powder Bed Fusion

In the laser powder bed fusion additive manufacturing process, the presence of porosity may result in cracks and significantly affects the part performance. A comprehensive understanding of the melt pool process dynamics and porosity evolution can help to improve build quality. In this study, a novel multi-physics computational fluid dynamics (CFD) model has been applied to investigate the fluid dynamics in melt pools and resultant pore defects. To accurately capture the melting and solidification process, major process physics, such as the surface tension, evaporation as well as laser multi-reflection, have been considered in the model. A discrete element method is utilized to model the generation of powder spreading upon build plate by additional numerical simulations. Multiple single track experiments have been performed to obtain the melt pool shape and cross-sectional dimension information. The predicted melt pool dimensions were found to have a reasonable agreement with experimental measurements, e.g., the errors are in the range of 1.3 to 10.6% for melt pool width, while they are between 1.4 and 15.9% for melt depth. Pores are captured by both CFD simulation and x-ray computed tomography measurement for the case with a laser power of 350 W and laser speed of 100 mm/s. The formation of keyholes maybe related to the melt pool front wall angle, and it is found that the front wall angle increases with the increase in laser line energy density. In addition, a larger laser power or smaller scanning speed can help to generate keyhole-induced pores; they also contribute to produce larger sized pores.

Implications of the melting depth and temperature of the Atlantic mid-ocean ridge basalts

Mid-ocean ridge basalts (MORBs) are characterized by large variations in trace element compositions and isotopic ratios, which are difficult to be interpreted solely by using magmatic process such as partial melting of a peridotitic mantle and subsequently fractional crystallization. Geochemical diversity of MORBs have been attributed to large-scale heterogeneity within the underlying mantle, and the heterogeneity might have been caused by addition of recycled crustal component, subcontinental lithosphere, metasomatized lithosphere and outer core contribution. In this study, we investigated the MORBs along the Mid-Atlantic Ridge (MAR) by estimating the temperature and pressure of partial melting, and comprehensively comparing trace element and isotope ratios. The data for MORBs from areas close to mantle plumes show large variations. Mantle plumes can affect mid-oceanic ridges 1 400 km away, but plume effects did not cover all of the ridge segments, and those segments without plume effects did not have any abnormalities in temperature, trace element or isotope ratios. We ascribed the above phenomena to result from the shapes of the plume flow, which we categorized as “pipelike channels” and “pancake-like channels”. The “pancake-like channels” plumes affected the ambient mantle nondirectionally, but the range of the mantle affected by the “pipe-like channels” plumes were selective. Element ratios of MORBs reveal that the mantle source of the MORBs along the MAR is highly heterogeneous. We suggest that most of source heterogeneities of the MORBs may be due to the presence of subducted slab and delaminated lower crust in the source. In addition, the plume that carried materials from the core-mantle boundary may affect some of the segments.

Simulation of the Divertor Target Shielding During Major Disruption in DEMO

Simulation of divertor target damage during thermal quench of the disruption in the future DEMO tokamak has been performed using the TOKES code. This parametric study includes damage estimation for disruptions of the plasma energy E0 in the DEMO core in the range of 0.4 to 1.3 GJ and of time duration 1 to 2 ms. According to the simulations, the maximum melt depth on the divertor targets is ~80 μm, independent of the energy content in the core. The melted pool maximum area grows from ~20 m2 for 0.4-GJ disruption to ~120 m2 for 1.3-GJ disruption. Maximum erosion depth is 4 μm for 1.3-GJ disruption and decreases to less than 1 μm with decreasing E0. The total quantity of vaporized tungsten ranges from 2 ∙ 1021 to 3 ∙ 1024 atoms for disruptions of 0.4 to 1.3 GJ. An additional parametric study has revealed weak dependence of the results from the characteristic widths λq of the disruptive flux in the scrape-off layer.

Ore-blending optimization for Canadian iron concentrate during iron ore sintering based on high-temperature characteristics of fines and nuclei

Canadian iron concentrate (CIC) can elevate the ferrous grade and lower the contents of gangue components and harmful elements in the sinter. To understand high-temperature characteristics of CIC and typical iron ore, the formation of the melt was calculated mainly through FactSage 7.2, and melt fluidity (MF) test for iron ore fines and penetration characteristic test of CIC melt into iron ore nuclei were carried out via micro-sintering method. The results show that hematite, calcium ferrites, dicalcium silicate, and magnetite take part in the formation of the melt in N2. The formation temperature of the liquid for CIC is higher than that for hematite/limonite ore. The MF of CIC is lower than that of hematite/limonite ore fines. The MF of hematite/limonite ore fines is dominated by the liquid amount and melt viscosity. The penetration depth (PD) of CIC melt into limonite ore nuclei is smaller than that into hematite ore nuclei. The PD is related to the reaction ability of the nuclei with the melt. Based on above results, sinter pot tests were conducted. The result shows that in the base ore blends including two hematite ores and two limonite ores, adding CIC deteriorates the sintering indexes. Increasing the proportion of high-MF and small-PD hematite ore can significantly improve the sintering indexes. 10 mass% is a suitable proportion for adding CIC in ore blends.

Statistics and segmentation: Using Big Data to assess Cascades arc compositional variability

Abstract Primitive and mafic lavas erupted in the Cascades arc of western North America demonstrate significant patterns of along-arc heterogeneity. Such compositional diversity may be the result of differences in mantle melting processes, subduction geometry, regional tectonics, or compositions of the slab, mantle, or overlying lithosphere. Previous authors have partitioned the arc into four geochemically distinct segments in order to assess the importance and relative roles of these processes (Schmidt et al., 2008). However, despite the significant amount of data available from the Cascades arc, no previous study has utilized a statistical approach on a comprehensive dataset to address arc segmentation and its petrogenetic causes. To better characterize the heterogeneity of the entire arc, we first compiled >235,000 isotopic, major, and trace element analyses (glass and whole rock) from over 12,000 samples, which range in composition from mafic to felsic, and include data from arc-front and back-arc centers. We focus on the 2236 mafic arc-front samples in our compilation in order to assess potential causes for along-arc differences in less differentiated magmas, and to potentially lessen any effect of crustal assimilation. To minimize inherent sampling bias – the effect where well-studied volcanoes heavily weight conclusions – we use a weighted bootstrap Monte Carlo approach in which the probability of a sample being selected to the posterior distribution was inversely proportional to the number of samples within its 0.25° latitude bin. This methodology produces a more uniform and unbiased distribution from which we can assess regional, rather than local, compositional variability in the Cascades arc. Using a multivariate statistical approach, we demonstrate that the four segments designated by Schmidt et al. (2008) are, in fact, statistically distinct. However, using a modified hierarchical clustering mechanism, we objectively divide the arc into six regions which have geochemical differences that are up to 6.3 times more statistically significant than in the previous scheme. Our new, more robust segmentation scheme includes the Garibaldi (49.75–51°N), Baker (48.5–49.75°N), Glacier Peak (47.75–48.5°N), Washington (45.75–47.75°N), Graben (44.25–45.75°N), and South (41.25–44.25°N) Segments. By partitioning the arc into the most statistically distinct segments and calculating unbiased mean compositions for each, we explore the petrogenetic causes for the regional-scale differences in primitive lava compositions. These bootstrapped mean data indicate significant inter-segment differences in fluid-flux signature, mantle fertility, and depth and degree of melting. We suggest that differences in subduction geometry, regional tectonics and mantle heterogeneity are the primary causes for these intra-arc differences.

Transition metals in komatiitic olivine: Proxies for mantle composition, redox conditions, and sulfide mineralization potential

AbstractWe present the results of a comprehensive study on the concentrations of first-row transition elements (FRTE: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn), as well as Ga and Ge, in liquidus olivine from 2.7–3.5 Ga old Al-undepleted and Al-depleted komatiites from the Kaapvaal and Zimbabwe Cratons in southern Africa, the Yilgarn Craton in Australia, and the Superior Craton in Canada. The sample set includes komatiites that remained sulfur-undersaturated upon emplacement, as well as komatiites that reached sulfide saturation owing to assimilation of crustal sulfur.All olivine grains display concentrations of Mn, Zn, Ge, Co, Fe, Mg, and Ni similar to the Bulk Silicate Earth (BSE) values, with significant negative anomalies in Sc, Ti, V, Cr, Ga, and Cu. Olivine from the studied Al-depleted komatiites displays on average higher 100×Ga/Sc ratios (>5) than olivine from Al-undepleted komatiites (≤5). Because garnet preferentially incorporates Sc over Ga, the data suggest that elevated Ga/Sc ratios in komatiitic olivine are indicative of garnet retention in the source region of komatiites, highlighting the potential of olivine trace element chemistry as a proxy for the depth of komatiite melting and separation of the magma from the melting residue. Copper concentrations in the studied olivine grains are controlled by sulfur saturation of the host komatiite during olivine crystallization. Olivine from sulfur-undersaturated komatiite systems displays Cu concentrations mostly between 1 and 10 ppm, whereas olivine from sulfide-bearing komatiites has Cu contents of <0.5 ppm. Because komatiites contain some of the world's highest metal tenor magmatic Ni-Cu sulfide deposits, the Cu variability in olivine as a function of the sulfide-saturation state highlights a potential application of olivine chemistry in the exploration for sulfide ore deposits.Olivine from the Paleo-Archean (3.5–3.3 Ga) komatiites displays overall higher V/Sc ratios (V/Sc = 2.1 ± 0.96; 2 S.D.) than olivine from their Neo-Archean (2.7 Ga) counterparts (V/Sc = 1.0 ± 0.81, 2 S.D.). Vanadium and Sc behave similarly during partial melting of the mantle and are similarly compatible in majorite garnet. However, V is redox-sensitive and its compatibility in olivine increases as the system becomes less oxidized, whereas Sc is redox-insensitive. We argue that olivine from the studied Paleo-Archean komatiites crystallized from more reduced magmas than their Neo-Archean counterparts. Elevated Fe/Mn ratios in olivine from Paleo-Archean komatiites mimic the V/Sc signatures and are interpreted to reflect that Fe2+ is more compatible in olivine than Fe3+. These results imply that V/Sc and Fe/Mn in komatiitic olivine may potentially provide insight into the evolution of the oxidation state of the Archean mantle. Additional studies that integrate the chemistry of komatiitic olivine with those of relict interstitial glass and melt/fluid inclusions are encouraged to fully understand and quantify the potential of FRTE in olivine as a proxy for the oxidation state of the mantle sources of komatiite magmas.

Geochemical characterization of a reconstructed 1110 Ma Large Igneous Province

1110 Ma Large Igneous Province (LIP) fragments in the Kalahari craton, southern Africa (Umkondo LIP); Dronning Maud Land, Antarctica; Bundelkhand portion of Indian craton (Mahoba dolerite dykes); Congo craton (Huila-Epembe dolerite dykes); and Amazonia (Rincon del Tigre-Huanchaca LIP) have been reconstructed as a single LIP with plume centre beneath the NW part of the Kalahari Craton. This paper offers the best estimates for the paleoposition of the Indian and Amazonian cratons along with conjoined Kalahari-SF/Congo reconstruction. This 1110 Ma mafic magmatism is dominantly tholeiitic, ranging from basalt to andesitic basalt in composition, generated over a range of mantle melting depths [(Gd/Yb)N = 1.2–2.3], exhibit low to high contamination with crustal components (negative Nb anomalies, eNd (0 to −12), and elevated Th/Yb). The data fall into two Groups based on TiO2 content, with Group 1 (low Ti) of andesitic basalt composition, and Group 2 (high Ti) exhibiting a basaltic affinity. Group 1 magmas were generated in the spinel lherzolite field followed by significant contamination likely during passage through metasomatised lithospheric mantle in crustal magma chambers. A greater melting depth reaching into the garnet lherzolite field is proposed for the Group 2 magmas. The majority of Group 2 units are located in the Kalahari and Congo cratons, and this reflects onset of deeper melting closer to the interpreted plume axis in our reconstruction.

Melting and solidification behavior of Ti-6Al-4V powder during selective laser melting

To investigate melting and solidification behavior during selective laser melting (SLM), the shape of the solidified materials and energy balance during SLM were evaluated through temperature measurements with a two-color pyrometer. The laser power and scanning speed were selected as parameters to melt Ti-6Al-4V powder in a square area. The input energy per unit area used during SLM was 5, 10, 16, or 20 J/mm2. The melting depth and width increased as the input energy increased. However, the aspect ratio of the melted area was constant. The mass ratio of melted to sintered material decreased as input energy increased. It was considered that the surplus input energy was used for sintering when the energy was high. Color maps show that the surface temperature distribution around the laser irradiation area was asymmetric, in which the temperature gradient at the solidified material side was smoother than that at powder side. The temperature history showed that melting and solidification occurred repeatedly during irradiation.

Effect of scanning speed on the solidification process of Al2O3/GdAlO3/ZrO2 eutectic ceramics in a single track by selective laser melting

Abstract Al2O3/GdAlO3/ZrO2 ternary eutectic ceramics with fine microstructure were directly fabricated from mixed pure ceramic powders by selective laser melting. The specimen forming quality, molten pool morphology and microstructure characteristic were investigated as functions of scanning speed. Solidification defects such as cracks and pores were effectively suppressed when the scanning speed was 12 mm/min. The relative density of the as-solidified eutectic specimens decreased from 98.7% to 95.7% with increasing the scanning speed up to 48 mm/min. The melting in this study was governed by conduction mode, leading to a decrease tendency of both melting width and depth with the increase of the scanning speed. Different from ordinary cognition, the eutectic spacing in top zone of the molten pool first decreased and then increased with increasing the scanning speed from 6 mm/min to 48 mm/min. The transition point appeared at 12 mm/min, where the dominant factor affecting the solidification rate changed from the scanning speed to the value of the angle between microstructure growth direction and laser scanning direction.

Pulsed laser melting of bismuth telluride thermoelectric materials

While laser melting, deposition, and annealing of semiconductor thin films are well-established, pulsed laser processing of bulk semiconductor material powders has been minimally investigated. This work investigates nanosecond pulsed laser melting of bismuth telluride, a common thermoelectric material. Using both experimental and computational modeling methods, a process window was determined in which melting is achieved before ablation occurs. The process window was determined for Bi2Te3 powder compacts, with melt depths on the order of 20–100 μm. The melted region had a fine-grained, columnar microstructure and showed typical selective laser melting defects such as microcracking. Stroboscopic imaging was used as an in situ imaging technique to observe molten pool features, revealing a teardrop-shaped molten pool with little resolidification between pulses. A simplified thermal model of the nanosecond pulsed laser melting process was developed, and two models for the solid phase thermal conductivity were used to investigate the impact of thermal conductivity on the size, shape, and duration of the molten pool. The results demonstrate the narrow process window available for pulsed laser processing of bulk bismuth telluride powders, and the discussion includes thermal management approaches possible for reducing defects such as microcracking.

Theoretical analysis of bubbles nucleating on surfaces of convex spherical inclusions in molten steel during vacuum treatment

Based on the theory of classical solidification nucleation, a thermodynamic model of bubbles nucleating on surfaces of convex spherical inclusions in molten steel was established. The expression of bubble critical-nucleation radius was derived. The differences between bubbles nucleating on convex spherical surface and flat substrate were discussed. The results show that the radii of spherical inclusions determine the degree of deviation on the two types of nucleation under same conditions and bubbles are more easily generated by flat substrate nucleation. In addition, the degree of deviation between the two types of nucleation decreases with the decrease of melt depth. The results also show that bubbles are easier to nucleate on the surface of inclusions with large radius or poor wettability. For a determined bubble critical-nucleation radius, the radii of spherical inclusions, the contact angles of spherical inclusions and the pressure of vacuum treatment have little influence on the depth range of bubble nucleation, while the pretreatment pressure shows significant impact on that. The probability of bubble nucleation reduced with the increase of melt depth, which was verified by related experiments.

The effect of anisotropic surface tension on interfacial evolution of a particle in the binary alloy melt

The dynamics of interfacial evolution of a particle in the binary alloy melt affected by anisotropic surface tension is studied by means of the multiple variable expansion method. The resulting analytical solution reveals the critical radius of nucleation in the binary alloy melt and the inward growth mechanism of interfacial evolution of the particle induced by the anisotropic effect of surface tension in the initial crystal growth immediately after nucleation. After nucleation, because of the anisotropic effect of surface tension, some parts of its interface grow outward, while some parts first grow inward in the initial crystal growth. Until the inward growth attains a certain distance (which is defined as ‘the melting depth’), these parts start to grow outward with other parts. During such a process the interface of the particle will form a remarkable concave and convex formation with the ear-like shape whose radius for some parts of the particle may be less than the critical radius of nucleation. The solute diffusion in the binary alloy melt changes the critical radius of nucleation and decreases the anisotropic effect of surface tension on interface deformation.

Impact of UV Nanosecond Laser Annealing on Composition and Strain of Undoped Si0.8Ge0.2 Epitaxial Layers

Ultraviolet Nanosecond Laser Annealing (UV-NLA) was performed on 30 nm-thick Si0.8Ge0.2 epitaxial layers. The various regimes encountered, depending on the melt depth after single pulse UV-NLA, are described and discussed in this paper. Energy densities around 2.00 J/cm² and above led to the formation of pseudomorphic layers with a strong Ge redistribution. Starting from uniform Si0.8Ge0.2 layers, Ge segregation toward the surface resulted in the formation of a Ge-rich surface layer with up to 55 at.% Ge for 2.00 J/cm². Such pseudomorphic SiGe layers with a graded composition and a Ge-rich surface may find promising applications such as contact resistance lowering in doped layers.

Microscopic Study on Mechanical Properties of Different Microregions during In-Service Welding

In-service welding has been gaining considerable attentions due to its significant economic benefits. At high temperature, several technical difficulties exist during repair process and burn-through has been one of the critical issues. To reveal the physical nature of burn-through, finite element simulation and molecular dynamics simulation are combined to investigate the micro dynamic properties of different micro regions in welded joint and the effect of crack on the microdynamic behavior in the process of material failure. The results indicate that burn-through is a failure process under the effect of tensile stress and high temperature. The performance near fusion line is the worst and a burn-through tends to occur at the regions behind maximum melting depth. The failure process of welded joints experience the initiation and development of micro defects. Continuous expansion of micro holes and micro cracks causes the structural fracture. Furthermore, the micro crack would decrease the structural strength and the failure mode differs for cracks in different direction. Failure process of crack structure has experienced the crack tip passivation and dislocation emission. And the formation of stacking fault is carried out in failure process. This paper reveals the microscopic mechanism of burn-through at the atomic level and provides a scientific basis for the continuous and safe operation of gas pipelines.

CHARACTERISTIC FEATURES OF THE SURFACE RELIEF FORMATION OF METALS MODIFIED BY COMPRESSION PLASMA FLOWS

Action of compression plasma flows (CPF) is a promising high-energy method for material modification ensuring uniform distribution of components in ultradeep (to about 100 μm) modified layers. In the present paper, using the scanning electron microscopy, we studied the surface relief and the thickness of a modified layer of W108 steel treated with compression plasma flows. To generate a plasma flux under experimental conditions, a magnetoplasma compressor of compact geometry with an energy storage battery of 15 kJ was used. It was established that during CPF action, the molten layer of material under the action of high-density plasma spreads over the surface. After the end of exposure, at the stage of rapid crystallization of the melt, a developed surface relief is formed with a height difference from 1 to 80 μm. With increase in the energy parameters of the acting CPF, the surface irregularities first increase and then decrease again, which is associated with the melt entrainment in the liquid phase. The dependence of the average melting depth of steel on the power density of the CPF action has been established. It is shown that the heat transfer model based on the Stefan problem allows one to predict the average melting depth of the target with sufficient accuracy; however, to determine the actual thickness of the modified layer, hydrodynamic entrainment and surface irregularities should be taken into account.

Experimental investigation of focusing cathode region by cooling tungsten

Arc plasma is an important heat source for manufacturing. In TIG welding, arc properties can be influenced by the dynamic thermal behavior in the cathode region. In this study, to experimentally verify the focusing feasibility of cathode region by cooling the tungsten, a highly cooled tungsten TIG torch was proposed and designed. Based on the imaging sensor equipped with a near-infrared filter, high temperature cathode region (HTCR) images in the cathode tip were captured. From the image sequence, height and width of the HTCR were extracted after camera calibration. The stagnation ablation experiments were carried out with welding currents ranged from 100 A to 500 A. In the highly cooled torch, HTCR size parameters were smaller comparing to those obtained with the less cooled torch, the resultant anode diameter is also constricted with an increasing melting depth. The focusing effect of the cathode region in the cooling tungsten was experimentally verified and was analyzed in view of thermal balance. The research provides a new method to modify the arc properties in TIG welding process.

Fluid-present anatexis of Neoarchean tonalite and amphibolite in the Western Shandong Province

Metatonalite and amphibolite from the Taishan region of the Western Shandong Province in the North China Craton record c. 2.60 Ga fluid-present partial melting via the breakdown of biotite, plagioclase and quartz to produce peritectic hornblende and anatectic melt. Eight paired leucosome–melanosome samples from metatonalite and three paired samples from amphibolite were investigated to evaluate the composition of the melt. Hornblende, biotite and plagioclase in the leucosomes and hornblende and plagioclase in melanosomes from both rock types have similar compositions. Two leucosome samples from the metatonalite were influenced by the removal of heavy rare earth element-rich hornblende and the accumulation of plagioclase. The other leucosomes are interpreted to represent near initial melt compositions with a minor component of peritectic hornblende and are enriched in Si, Na and Sr and depleted in K, Ca, Ba and Rb relative to melanosomes. The enrichment of Na in the melt is inconsistent with experimental results of fluid-present melting of tonalite, but is broadly consistent with the experimental results of fluid-fluxed melting of amphibolite. The absence of K-feldspar in both rock types is a critical control on the composition of anatectic melt and initial melt compositions were probably similar for both rock types. Leucosomes inherited rare earth element patterns from their sources, which suggests that some trace element diagrams used to infer tectonic settings and depths of melting are not appropriate for reworked components of Archean grey gneisses. Whole-rockδ18O suggest that the fluids responsible for inducing local melting were derived from the intrusion and crystallization of ~2.60 Ga tonalites and trondhjemites in the Taishan region. One amphibolite sample has a relatively low δ18O suggestive of interaction with meteoric water or seawater possibly related to crustal extension and asthenosphere upwelling at ~2.60 Ga. Fluid-present partial melting reworked 2.75–2.60 Ga tonalites and amphibolites, generating ~2.60 Ga sodium-rich components of grey gneisses in the Western Shandong Province.

Determination of the particle content in laser melt injected tracks

Surfaces of machine parts or tools are subjected to corrosive stresses or wear. To increase the wear resistance of surfaces, metal matrix composite (MMC) can be applied. For higher wear resistance, it is important to achieve a high particle content and a homogenous particle distribution. In this work, aluminium bronze substrate was reinforced by spherical fused tungsten carbides via laser melt injection. The laser power, travel speed and powder mass flow were varied. The influence of these process parameters on the hard particle content was investigated in single tracks. Furthermore, laser melting and laser melt injecting were compared. Laser melt injecting resulted in a significant increase in the track volume. Analytical calculation showed that the volume increase was higher than the volume of the injected particles. Single tracks composed of MMC could be produced without cracks and pores. Depending on the energy input per unit length, undesired melting of the particles was observed. The particle content was investigated via binary pictures from metallographic cross-sections using two different software packages. An approach to calculate the particle content as a function of the width, depth and height of laser melt injected tracks via circle segments is presented.