For the investigation of vapour explosions, droplet impingement experiments were performed with the binary system Pb–Sn and the pseudo-binary system PbS–Cu2S. The experiments were performed with a ...melt at 600 °C (Pb–Sn) or 700 °C (PbS–Cu2S) and a water bath at ambient temperature and pressure. A hydrophone and a high-speed camera were used to study the interaction and from this data, the explosion probability and intensity were determined.
The explosion probability had a single minimum around 70 wt% Sn, close to the eutectic composition. Moreover, the explosion probability increased approximately linearly with changing composition towards the pure melts, and was similar for pure tin and pure lead. On the other hand, the explosion intensity was comparable for tin and the eutectic alloy while clearly lower for lead. Almost all intermediate alloys had a reduced explosion intensity.
Based on the variation in composition, the effects of the liquidus or solidus temperature and the liquidus-solidus gap on the explosion behaviour were also investigated. The explosion probability in both systems increased with increasing liquidus temperature. Also, the maximum explosion intensity in the Pb–Sn system increased with increasing liquidus temperature. Both could be related to easier triggering due to (partial) solidification. On the other hand, the explosion intensity was found to decrease with increasing gap between liquidus and solidus temperature, as was also found in literature. No significant trends for the explosion intensity were found for experiments with PbS–Cu2S.
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•With Pb–Sn, lowering the liquidus-solidus gap increased the explosion probability.•With PbS–Cu2S, raising the liquidus-solidus gap increased the explosion probability.•No statistically significant trend for the hydrophone peak signal.•With PbS–Cu2S, the explosion intensity showed no statistically significant trend.•With Pb–Sn, the explosion diameter increased with decreasing liquidus-solidus gap.
The thermal cycle during dissimilar friction spot welding of Al alloy AA5754 to Mg alloy AZ31 was measured by thermocouples located in the weld region. The results revealed that the weld is exposed ...to a non-equilibrium solidus temperature induced by rapid heating and cooling. Microstructural analyses showed that the grain structure development in the stir zone was affected by grain boundary diffusion, interfacial diffusion and dynamic recrystallization, which resulted in fine equiaxed grains of Al12Mg17 in the weld center.
One of the central challenges in accurately estimating the mantle melting temperature is the sensitivity of the probe for detecting a small amount of melt at the solidus. To address this, we used a ...multichannel collimator to enhance the diffuse X‐ray scattering from a small amount of melt and probed an eutectic pyrolitic composition to increase the amount of melt at the solidus. Our in situ detection of diffuse scattering from the pyrolitic melt determined an anhydrous melting temperature of 3,302 ± 100 K at 119 ± 6 GPa and 3,430 ± 130 K at the core‐mantle boundary (CMB) conditions, as the upper bound temperature. Our CMB temperature is approximately 700 K lower than the previous estimates, implying much faster secular cooling and higher concentrations of S, C, O, and/or H in the region, and nonlinear, advocating the basal magma ocean hypothesis.
Plain Language Summary
The heat stored in the Earth's deep interior has been the primary fuel for a range of global processes from mantle convection to surface tectonics, but quantitative estimation of the heat remains uncertain. The melting temperature of mantle materials is one of the key parameters to understanding the thermal evolution and present‐day state of the Earth's interior, but it has been poorly constrained, with recent measurement discrepancies as large as 600 K. Here, we report melting temperatures of mantle compositions measured over a wide range of pressures expected for the lower mantle. We investigated a eutectic mantle composition using multichannel collimator filtered X‐ray diffraction in combination with the laser‐heated diamond‐anvil cell. Fitting our melting data over the range of 46–145 GPa led to a solidus temperature of 3,430 ± 130 K at the core‐mantle boundary. This temperature is approximately 700 K lower than the previous estimates, implying much faster secular cooling at the lower mantle than previously believed. Furthermore, our solidus curve constrained for a wide pressure range is strongly nonlinear and thus supports the basal magma ocean hypothesis.
Key Points
Combined usage of multichannel collimator and laser‐heated diamond‐anvil cell improved detection of silicate melt
This led to the lowest solidus temperature of anhydrous pyrolite, 3,430 ± 130 K, at the core‐mantle boundary conditions
We advocate Fe‐enriched provinces at the core‐mantle boundary to be originated from the magma ocean
•An analytical solution of the solidification equations of steel was obtained.
An approximate analytical model has been developed to obtain simultaneous solutions for nonlinear solute- and ...heat-transfer equations for multi-component alloy steels; in this model, a linear relation between the solid fraction and the temperature in the mushy zone was assumed. This model predicts important parameters, such as the solidus temperature for the multi-component steel materials that have not been well confirmed by the reliable measurement in a real process. The predicted temperature, solidification constants, and effective partition ratios of solutes were in good agreement with both the reported measurements and generally accepted values. The predicted solidus temperatures were also in reasonable agreement with the reported zero ductile temperature of Fe–C–Mn steel and the thermo-analytically measured solidus temperatures of steels of various grades. The solutions were also in good agreement with those separately performed numerical thermal analysis. The model involves the solution for Fe-C binary alloy which is consistent with the Neumann’s solution in the low carbon range. Thus, this model provides approximate analytical solutions that can reduce the computational load, saving time and cost.
When cemented carbide contacts molten cast iron during the insert casting process, the binder phase of the cemented carbide is thought to melt even if the molten temperature of the cast iron is ...lower than the solidus temperature of the cemented carbide (1593 K). It is important to understand the melting mechanism to clarify the interface formation mechanism, and subsequently control the interface structure. The purpose of this study is to clarify the interface formation mechanism from the microstructural change of cemented carbide dipped in molten cast iron. A round bar specimen made of cemented carbide was dipped in molten cast iron at 1473 to 1596 K, and pulled up after a predetermined time. Microstructure observation, elemental analysis, and hardness test were performed on the cross-section of the specimen. The specimen changed from a homogeneous sintered structure to a two-layer structure, the center side was a non-reacted layer that did not change, and the outer side was the transition layer where melting had occurred. The diffusion of Fe and C is thought to have decreased the solidus temperature of the binder phase significantly that the binder phase melted. The non-reacted layer radius could be expressed by the rate equation derived from the Nernst-Brunner equation. Structural changes were seen at the interface such as increased outer diameter of the cemented carbide round bar specimen, occurrence of shrinkage cavities in the transition layer, and characteristic concentration of Co at the boundary. These are thought to be due to liquid phase migration occurring in the molten binder phase and decreased WC solubility due to the increase in Fe concentration.
The knowledge on constitutive mechanical behavior at the temperatures close to the solidus is essential for predicting high-temperature deformation and fracture, e.g. cold and hot cracking of ...aluminum alloys. In this work we studied the tensile mechanical properties of an as-cast AA7050 alloy in a near-solidus temperature regime. Tensile tests were carried out using Gleeble-3800™ system at temperatures from 400 to 465°C and at strain rates from 0.0005 to 0.05s−1. The results show that the strength decreases with increasing temperature and decreasing strain rate. Meanwhile, ductility decreases with the increase of temperature and strain rate. The constitutive parameters were extracted by fitting the test data to the extended-Ludwik and creep-law equations. The parameters for the extended-Ludwik equation are continuous with the values from a lower temperature regime obtained earlier, while the parameters for the creep-law equation are comparable with those obtained on other 7XXX aluminum alloys. We observed a change in fracture mode at 450°C; from ductile transgranular to intergranular. This temperature coincides with the discontinuity point of the temperature-ductility slope. On the fracture surface of a sample that was deformed at 465°C with a strain rate of 0.0005s−1, we observed features characteristic of micro-superplasticity. Considering the test conditions, viscous flows of incipient melt or liquid-like substances are suggested to be responsible for the formation of this feature.
During the extrusion of aluminum alloys profiles using porthole dies, the temperature of the material in the welding chamber is one of crucial parameters determining the quality of longitudinal ...welds. In order to extend the permissible temperature range, the billets intended for this process should be characterized by the maximum attainable solidus temperature. Within the present work, the homogenization of AlZnMgCu alloys DC-cast (Direct Chill-cast) billets was investigated, with the aim of solidus temperature maximization. Conditions of soaking and cooling stages were analyzed. The materials were homogenized in laboratory conditions, and the microstructural effects were evaluated on the basis of DSC (Differential Scanning Calorimetry) tests and SEM/EDS (Scanning Electron Microscopy/Energy-Dispersive Spectroscopy) investigations. For all examined alloys, the unequilibrium low-melting microstructure components were dissolved during soaking, which led to the significant solidus temperature increase, in comparison to the as-cast state. The values within the range of 525–548 °C were obtained. In the case of alloy with highest Cu concentration, the application of two-step soaking was necessary. In order to take advantage of the high solidus temperature obtained after soaking, the cooling rate from homogenization must be controlled, and the effective cooling manner is strongly dependent on alloy composition. For high-Cu alloy, the solidus decreased, despite the fast cooling and the careful billets preheating being necessary.
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