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The transformation of liquid–solid interface induced by the steady magnetic field (SMF) in the directionally solidified Ni-10 wt pct Cr alloy was studied experimentally. At the moderate pulling rate (50 μm s−1), it could be observed that the interface morphology gradually transformed from planar to cellular shape with increasing the SMF intensity (0 T, 3 T, 6 T). However, the cellular interface at the high pulling rate (100 μm s−1) was not influenced by the SMF. 3D numerical simulations suggested that the transformation of interface morphology originated from the thermoelectric magnetic convection near the wavelike interface at the early stage of solidification. From the composition measurement, it was found that the formation of microsegregation at the moderate pulling rate was associated with the interface morphology. Under the 3 T SMF, the liquid–solid interface remained planar and the microsegregation level increased in comparison with that without the SMF. Under the 6 T SMF, the liquid–solid interface became cellular and the microsegregation level was reduced. The factors affecting microsegregation were evaluated. The effective partition coefficient was estimated based on composition data. It was revealed that the effective partition coefficient increased with the 6 T SMF due to the thermoelectric magnetic and magnetic damping effects within the cellular structure. Additionally, the solid diffusivity was measured using the diffusion couple technique. It was found that the interdiffusion coefficient of Cr decreased with increasing the SMF intensity. The modified Brody model was used to predict the microsegregation behavior in the SMF. The predicted results were in agreement with experimental observation. It could be concluded that the decrease in solid diffusivity enhanced the formation of microsegregation for the planar interface, whereas the increase in effective partition coefficient in the SMF was beneficial for alleviating the extent of microsegregation for the cellular interface.

The grain refinement of 2024 Al alloy inoculated with Al-5Ti-1B master alloy in a steady magnetic field (SMF) was investigated. It was shown that the degradation in grain refinement was enhanced and a cellular–dendritic transition of equiaxed primary α-Al grains occurred under the SMF. Employing a differential scanning calorimeter, the nucleation temperature of primary α-Al phase was found to decrease in the SMF, i.e., the undercooling was enhanced, and the kinetics of phase transformation was modified in the SMF. The enhanced degradation in grain refinement and increase in undercooling are attributed to the modified solid/liquid interfacial free energy and the delay of formation of critical nucleus due to the retarded migration rate of atoms in the liquid phase in the SMF. The cellular–dendritic transition of primary α-Al grains is ascribed to the modified constitutional undercooling at the solid/liquid interface, which results from the change in solute distribution by the damped convection and retarded diffusivity in the SMF. Additionally, the increase in growth dimension and the modified solid/liquid interfacial free energy under the SMF are also responsible for the enhanced constitutional undercooling and the cellular–dendritic transition.

The effect of hot isostatic pressing on the tensile property of single crystal superalloys at elevated temperature is studied experimentally. The results show that the high temperature elongation of nickel based single crystal superalloys is obviously enhanced by hot isostatic pressing, while the yield strength is unchanged. Besides, it is found that the hot isostatic pressing causes the change of fracture surface. The enhancement of elongation and the change of fracture behavior are discussed.

The thermal and numerical simulation of the mould electromagnetic stirring (M-EMS) during continuous casting (CC) of the GCr15 bearing steel was performed. The thermal simulation apparatus ...

Experimental investigations on microsegregation during directional solidification of two Al–Cu alloys with and without a steady magnetic field (SMF) were carried out. The solidification morphologies and microsegregation behaviors were examined. The amount of non-equilibrium eutectics and the concentration versus solid fraction profiles were obtained. The results indicated that the amount of microsegregation was increased under an SMF when the solid/liquid interface was planar. For cellular and dendritic growth, however, the SMF alleviated the microsegregation level. The change of the factors affecting microsegregation under the SMF was analyzed. The reduction in solid diffusion coefficient in an SMF aggravated the microsegregation level, while the thermoelectric magnetic convection (TEMC) was found to have a positive effect. It was concluded that the change in microsegregation in different conditions might be attributed to the combined action of solid diffusion suppression and TEMC in mushy zone under an SMF. Based on Brody model, the microsegregation behavior in an SMF was predicted. The calculated results were in agreement with experiment observations.

The microsegregation behavior of the Al-4.5 wt%Cu alloy solidified at different cooling rates under the alternating magnetic field (AMF) was investigated. The experimental results showed that the amount of non-equilibrium eutectics in the interdendritic region decreased upon applying the AMF at the same cooling rate. The change in microsegregation could be explained quantificationally by the modifications of dendritic coarsening, solid-state back diffusion and convection in the AMF. The enhanced diffusivity in the solid owing to the AMF was beneficial for the improvement in microsegregation compared to the cases without an AMF. In contrast, the enhanced dendritic coarsening and forced convection in the AMF were found to aggravate the microsegregation level. Considering the contributions of the changes in above factors, an increase in solid diffusivity was found to be primarily responsible for the reduced microsegregation in the AMF. In addition, the microsegregation in the AMF was modeled using the analytical model developed by Voller. The calculated and experimental results were in reasonable agreement.

The effects of forced flows at different velocities on microstructure and solute distribution during the directional solidification of Sn-10 wt% Bi alloys under a simultaneous imposition of a transverse static magnetic field (TSMF) and an external direct current (DC) have been investigated experimentally and numerically. The experimental results show that the solid-liquid interface will gradually become sloping with the increase of the forced flow velocity when the thermoelectric magnetic convection (TEMC) dominates the forced flow at solidification front. However, the interface will gradually become planar as the flow velocity further increases when the electromagnetic convection (EMC) dominates the forced flow. Moreover, when the flow velocity gradually increases, the primary dendrite spacing decreases from 384 to 105 μm accordingly. The simulation results show that the solute distribution at the two sides of the sample can be significantly changed by the forced flow at solidification front. The rejected solute will be unidirectionally transported to one side of the sample along the TEMC (a low-velocity forced flow), thereby causing the formation of a sloping interface. However, the rejected solute will be returned back along the EMC (a higher-velocity force flow), which results in a planar interface. Furthermore, the solute content at the two sides of the sample under the forced flows at different velocities was measured. The results are in good agreement with the simulation results, which shows that the solute content difference between the two sides of the sample reaches the maximum when a 0.5 T TSMF is applied, while the solute content difference decreases to zero with a simultaneous application of a 0.5 T TSMF and a 1.6 × 105 A/m2 external DC.

The formation of the microstructures in the hypo- and hypereutectic Al Cu alloys in the steady magnetic field (SMF) was investigated using the conventional quenching technique. In comparison with quenched structures without the SMF, the additional bulky phases, i.e. θ-Al2Cu phase and the supersaturated α solid solution, were found to form in the Al-26 wt%Cu and Al-45 wt%Cu alloys quenched in the SMF, respectively. The temperature measurements showed that the maximum cooling rate of the quenched sample in the SMF was markedly higher than that without the SMF and thus a larger undercooling was obtained in the SMF. The microstructure formation in the SMF can be rationalized using the Al Al2Cu phase diagram with metastable extensions and the coupled growth zone.

The effect of a two-step heat treatment including solution and aging heat treatments in an alternating magnetic field (AMF) on microstructure and mechanical properties of the Ni-based superalloy DZ483 was investigated. In the solution heat treatment, the AMF significantly reduced the chemical segregation. In the aging heat treatment, the application of the AMF was found to not only modify the partition ratios of some elements like Al and Ti between the γ′ precipitate and the γ matrix, but also to distinctly accelerate coarsening of γ′ precipitates and to result in a larger mean particle size. Additionally, the morphology of γ′ precipitates gradually evolved from a quasi cube without an AMF to a regular cubic shape in the AMF. Mechanical performance tests showed that hardness and tensile strength of the samples heat treated in the AMF were increased in comparison with those without an AMF. It is shown that the enhanced diffusivity in the AMF is mainly responsible for the change in microsegregation, particle size, and morphology evolution. Furthermore, the AMF promotes the solid solution strengthening and the order strengthening, both of which contribute to the improvement of mechanical properties.

Wettability of solids by liquid metals plays an important role in numerous technological processes. In this work, the effect of a steady magnetic field (SMF) on the wettability of copper and silica substrates by a Ga–In–Sn liquid alloy was investigated using the sessile drop technique. It was found that the contact angles on both substrates increased with increasing SMF intensity. The reduced wettability can be attributed to a change in liquid surface tension under the action of an SMF. In combination with the equations of state, the increase of the contact angle with the SMF intensity is predicted, which is in reasonable agreement with experimental results.

An external direct current (DC) was introduced to counteract the thermoelectric magnetic effect during the directional solidification of Sn-10 wt pct Bi alloy under a 0.5 T transverse static magnetic field. The results show that the single-side Bi segregation induced by the thermoelectric magnetic effect gradually becomes weakened, disappeared, and then reversed with the increasing current density of the external DC. Therefore, a new method for counteracting the thermoelectric magnetic effect during materials processing under the magnetic field was proposed. In order to verify this method, the absolute thermoelectric power of Sn-10 wt pct Bi alloy and the internal thermoelectric current under the experimental conditions were measured and calculated, respectively. A 2D numerical simulation was established to simulate the evolution of the solid–liquid interface morphology, flow field, and composition segregation with the increasing current density of the external DC during directional solidification under a transverse static magnetic field. The present study not only facilitates the understanding of the effects of the forced flows on the directionally solidified microstructures and composition segregation, but also provides a new way for eliminating segregation and obtaining the higher-quality solidification structure by using the electromagnetic compounding technique.

The effect of a high magnetic field on the γ′ phase of Ni-based single crystal superalloy during directional solidification is investigated experimentally. The results clearly indicate that the magnetic field significantly reduces the γ′ phase size. Further, the quenching experiment is carried out, and the results found that the length of mushy zone is obviously decreased under a high magnetic field. Based on both experimental results and nucleation mechanism, it is found that the decrease of γ′ phase size should be attributed to the fact that a high magnetic field causes the increase of temperature gradient in front of solid/liquid interface and leads to the increase of undercooling of γ′ phase.

For applying an alternating magnetic field (AMF) in materials processing it is of high significance to understand the physical mechanisms behind the change in diffusivity in the AMF. In this work, the effect of the AMF on interdiffusion in a Ni-Cr alloy was investigated with a diffusion couple. The interdiffusion coefficient was found to increase with increasing AMF intensity. The faster diffusivity is a consequence of the enhancement of the dislocation density in the diffusion couples that was confirmed by the broadening of X-ray diffraction peaks. The higher dislocation density is attributed to the magnetoplastic effect (MPE). Theoretical considerations on the relation of MPE, dislocation density and diffusivity are in agreement with the experimental results.

The effect of heat treatment with the aid of an alternating magnetic field (AMF) on chemical segregation and morphology evolution of γ′ precipitates in the DZ483 superalloy was investigated. It was found that the application of the AMF during heat treatment significantly reduced chemical segregation, increased the mean particle size and accelerated morphology transition. These phenomena could be attributed to the enhanced diffusivity of alloying elements in the AMF, which was proved by diffusion experiments.

The effect of heat treatment with the aid of a steady magnetic field (SMF) on microstructure and mechanical properties of the superalloy DZ483 was investigated. The SMF was found to reduce the average size of γ′ precipitates and also to delay their splitting in the dendrite core, but had no pronounced effect on the morphology of the precipitates in the interdendritic region. Measurement of the distribution of alloying elements showed that the degree of microsegregation in the samples heat treated in the SMF was higher than in those without the SMF. It is concluded that the SMF reduced the diffusivity of the alloying elements and thus decreased the coarsening rate of the precipitates, which led to a reduction of their average size and a delay of their splitting. With respect to the mechanical properties it was found that the Vickers hardness and the tensile strength of the samples after heat treatment in the SMF increased. According to the precipitation hardening theory, the Orowan process is the dominating deformation mechanism in DZ483 at a high temperature and thus the DZ483 samples with a smaller size of γ′ precipitates after heat treatment in the SMF showed a better tensile performance.

High magnetic fields are widely used to improve the microstructure and properties of materials during the solidification process. During the preparation of single-crystal turbine blades, the microstructure of the superalloy is the main factor that determines its mechanical properties. In this work, the effects of a high magnetic field on the microstructure of Ni-based single-crystal superalloys PWA1483 and CMSX-4 during directional solidification were investigated experimentally. The results showed that the magnetic field modified the primary dendrite arm spacing, γ′ phase size, and microsegregation of the superalloys. In addition, the size and volume fractions of γ/γ′ eutectic and the microporosity were decreased in a high magnetic field. Analysis of variance (ANOVA) results showed that the effect of a high magnetic field on the microstructure during directional solidification was significant (p

The creep properties of nickel-base single crystal superalloy CMSX-4 with and without high magnetic field at 980 °C/250 MPa are investigated. Superalloy CMSX-4 is shown with an excellent rupture life under high magnetic field. Fracture surface results indicate that small square-shaped facets are shown and microporosities are formed at the bottom of dimple without high magnetic field, while the dimple surface shows large square-shaped facets and microporosities disappear from the bottom of dimple with high magnetic field. The mechanism of the enhancement of rupture life and the change of fracture behavior are explored in detail.

The effect of primary dendrite orientation on stray grain formation in a cross-section change region during the directional solidification of Ni-based superalloy is investigated through both experimental observations and numerical simulation. The results clearly show that the orientation of primary dendrite affects the formation of stray grains in the cross-section change region. It is observed that, for the primary dendrite without misorientation, no stray grain is formed in the cross-section change region; for the primary dendrite with a moderate misorientation (15 deg), stray grains are formed only on the side converging from the mold wall in the cross-section change region. When the misorientation is 25 deg, stray grains are formed on both the side converging from the mold wall and the side diverging from the mold wall in the cross-section change region (the converging side and the diverging side for short). The simulation results are in accordance with experimental results. Furthermore, the correlation among factors such as stray grain formation, primary dendrite orientation, and withdrawal velocity has been analyzed. The mechanism of stray grain formation in various oriented primary dendrites is discussed.

The suppression of stray grains during seed melt-back of single-crystal superalloy through thermal resistance technique has been investigated based on both experimental observations and numerical simulation. The results indicate that the introduction of thermal resistance layer significantly suppresses the stray grain formation of single-crystal superalloy. Based on both theoretical analysis and numerical simulation, above results should be attributed to the decrease of radial heat transfer of sample in the thermal resistance layer.

Textured porous Si3N4 ceramics with fine and coarse β-Si3N4 powders as the raw materials were prepared by gel casting in a strong magnetic field of 6T and subsequent pressureless sintering. These results showed that highly textured porous Si3N4 ceramics could be obtained by adjusting the ratio between fine and coarse β-Si3N4 powders in 6T. The Lotgering orientation factor in green bodies showed the value of 0.72∼0.74 with the increase of coarse powder content. The sintering process promoted texture development of the samples by Ostwald ripening owing to the big difference in the β-Si3N4 initial powder size. After sintering at 1800oC for 2 h, the degree of texture (Lotgering orientation factor) in the sample, prepared with fine and coarse powders at the ratio of 1:1, reached the maximum value (0.91), and it had relatively high density (66.91%) and low apparent porosity (34.51%). The crystallographic texture in porous Si3N4 ceramics led to the anisotropic bending strength. The method combined with g...

The distribution rules of impurities contents in distilled metallic dysprosium were researched, and a theoretical analysis was carried out. The research results indicated that, the content of impurity in distilled metal, such as Al and Fe, was lower in the initial stage, increased slowly in the middle stage, and increased rapidly in the last stage during the process of distillation purification. The calculated method of separation coefficient of impurity in crude metal by content of impurity in distilled metal was not suitable for high pure metals, and the modified separation coefficient was proposed, and it equaled 1/6.1 and 1/16.9 for impurity Al and Fe. The physical process of distillation was coincident with that of solidification essentially, and solute re-distribution theory in solidifying front could be used to describe the impurity distribution near evaporating surface. In the former stage of distillation purification, the diffusion of impurity in liquid metal could reach a quasi-equilibrium state, the calculated result of impurity content in distilled metal agreed well with experiments. In the latter stage of distillation process, the diffusion rate of impurity in liquid metal decreased, and the content in distilled metal was larger than the calculated result.

The effect of a transverse magnetic field on stray grain formation during directional solidification of superalloy was investigated. Experimental results indicated that the transverse magnetic field effectively suppressed the stray grain formation on the side the primary dendrite diverges from the mold wall. Moreover, the quenched experimental results indicated that the solid/liquid interface shape was obviously changed in a transverse magnetic field. The effect of a transverse magnetic field on stray grain formation was discussed.

The Si3N4 ceramic was joined to DZ483 superalloy by partial transient liquid phase bonding using Ti/Au/Ni/Ti multi-interlayers. The interfacial microstructure and crystallographic orientations between the Si3N4 ceramic and the Ni interlayer were analyzed by scanning and transmission electron microscope. The results indicated that the interfacial microstructure of the joint consists of three main phases: a TiN reaction phase, an Au-rich phase, and a lamellar Ni-rich phase distributed homogenously in the Au-rich phase. The nano-scale wavy interface was observed at the Si3N4/TiN interface, which was thought to provide high mechanical strength. A possible mechanism for the formation of interfacial structure observed was discussed.

Silica ceramic cores prepared by heat-press molding were strengthened by impregnating silicone resin. The effect of heating treatment conditions on the properties of silica ceramic cores was analyzed. Results showed that the ambient bending strength increased from 9.3 ± 2.0 MPa to 24.8 ± 1.5 MPa by curing process at low temperature of 250 °C. However, further heating treatment at high temperature ranging from 1150 to 1300 °C made the strength of the samples lower than that of the cured samples owing to the decomposition of silicone resin. But the strength of the samples was still higher than that of raw samples. The increasing heating treatment temperature promoted an increase in the strength by a densification process.

The Al-4.5 wt%Cu alloy has been directionally solidified under a high static magnetic field up to 6 T. A novel α-Al dendrite morphology was presented when the primary trunk aligned to the magnetic field and temperature gradient. It is observed that tertiary dendrites grew asymmetrically on secondary arms in the plane perpendicular to the primary trunk, and a pinwheel-like pattern formed. A numerical simulation was performed using finite-element code COMSOL software to investigate the thermoelectric magnetic convection (TEMC) induced by the external magnetic field. The results show that the velocity of the TEMC increases with the increasing of the magnetic field and reaches a maximum value near 6 T. Meanwhile, the magnitude of the TEMC on two sides of the secondary arm becomes unequal. Comparison of the experimental and numerical results reveals that the development of the pinwheel-like appearance is in accordance with the flow pattern of the TEMC. It is implies that the modification of the tertiary dendrite could be attributed to the TEMC generated on dendrite scale. This work also provides direct experimental evidence that a high magnetic field (>1 T) induces fluid flow in mushy zone.

C-axis textured SiC ceramics were prepared by a strong magnetic field of 6 T assisted gel-casting and subsequent pressureless sintering. The optimal suspension parameters for gel-casting were determined by analyzing the influences of pH value and dispersant content on the stability and dispersibility of suspensions. The effect of sintering conditions on the texture development and properties of SiC ceramics was discussed. It was found that the increasing sintering temperature or holding time promoted the densification process of SiC ceramics. The c-axis of SiC grain was aligned parallel to the magnetic field by applying a strong magnetic field of 6 T. The degree of texture of SiC ceramics showed a slightly increasing trend with the increase of sintering temperature or holding time. When the samples were sintered at 1950 °C for 4 h or 6 h, the large elongated grains were formed in the samples, leading to the extremely evident anisotropic microstructure on different planes. Textured SiC ceramics exhibited the anisotropic bending strength.

The effects of a high magnetic field on microstructures during seed melt-back of superalloy were investigated. Experimental results indicated that the high magnetic field significantly modified the melt-back interface shape and the melt-back zone length. In addition, stray grain on the edge of sample was effectively suppressed in the high magnetic field. Based on experimental results and quantitative analysis, the above results should be attributed to the increasing temperature gradient in a high magnetic field.

Porous alumina based ceramics were fabricated by injection method, where alumina powders were used as raw materials and solvent silicone resin was used as binder. During the heat treatment process, an organic-inorganic transformation occurred in silicone resin. The increase of heating temperature promoted the formation of mullite phase when the temperature was higher than 1500°C. The weight loss of porous alumina based ceramics was maintained at 5.7∼5.9%. When the heating temsperature was 1500°C, porous alumina based ceramics showed the biggest shrinkage rate, lowest apparent porosity and highest bending strength.

The selective laser melting (SLM) technology is widely used for the manufacturing of Ti6Al4V alloy components in the biomedical and aerospace industries, and the residual pores are one of the significant defects obstructing its further application. X-ray computed tomography (XCT) technique was applied for the examination and analysis of the spatial and morphological features of pore defects, which will influence the tensile properties of the SLM-manufactured Ti6Al4V samples. Hence, the effects of processing parameters on pore defects and their formation mechanism are discussed thoroughly. The results showed that two major types of pore defects are observed: the lack-of-fusion caused by low volumetric energy density (VED), and the keyhole mode resulting from excessive energy densities. The highest relative density of 99.995% was obtained at a VED value of 58.8 J/mm3. Besides, the quantitative information of the porosity defects, such as size distribution, morphology and formation direction, was evaluated using XCT to reveal their formation mechanisms. Furthermore, the tensile properties of SLM-manufactured Ti6Al4V alloy under different VED values were evaluated to correlate with the porosity variation. Overall, the tensile strength and ductility were notably degraded with the increase of porosity. The fractography study based on XCT and SEM showed that lack-of-fusion and porosities are responsible for the early fracture. In conclusion, the XCT technique can provide direct and precise inspection of the process of laser-based additive manufacturing to control the overall quality.

The effect of a steady magnetic field on reactive diffusion in Ni–Al diffusion couples was investigated. The diffusion couples prepared by the electrodeposition technique were annealed in the temperature range of 530–590 °C with and without the magnetic field of 6 T. Regardless of the magnetic field, two intermetallic compounds, i.e., Ni 2 Al 3 and NiAl 3 , were present in the product layers of diffusion couples. NiAl 3 phase shows island-like structures at relatively lower temperatures while the Ni 2 Al 3 phase forms a typical layered structure. The growth of Ni 2 Al 3 layer was found to be parabolic. When the diffusion direction was perpendicular to the direction of the magnetic field, the external magnetic field reduced the growth rate of the Ni 2 Al 3 phase. Whereas the magnetic field had no obvious effect on the growth rate of Ni 2 Al 3 layers in the diffusion configuration of mutually parallel directions. The magnetic field intensity and direction dependence of growth rate of Ni 2 Al 3 intermetallic layers can be attributed to the change in number of collision of an atom with neighbors during diffusion due to spiral motion under the action of the Lorentz force, which leads to change the frequency factor, not activation energy, for layer growth.

The textured porous Al2O3 ceramics were prepared by slip casting in a strong magnetic field of 6 T and subsequently sintering. The c axis of Al2O3 grain was oriented parallel to the direction of the magnetic field and the textured porous microstructure with plate-shape grains was formed. The porosity of textured porous Al2O3 ceramic was 30.37% and the relative density reached 66.29% when the sintering temperature is 1600°C. The textured porous Al2O3 green body showed the linear shrinkage anisotropy. The bending strength of the textured porous Al2O3 ceramics depended on the alignment direction of plate-shape grains.

In this paper, the textured Si3N4 ceramics were prepared by adding seed particles during gel-casting in the magnetic field of 6 T, followed by pressureless sintering. The effect of pH on the stability and dispersibility of Si3N4 slurry and the effect of seed particles content on texture formation of Si3N4 ceramics were both studied. Those results showed that the slurry with good stability and dispersibility was obtained when pH was about 11.6. The a or b-axis of Si3N4 particles or crystals was aligned parallel to the direction of the magnetic field in the magnetic field of 6 T. The degree of texture of Si3N4 ceramics further increased during sintering. With the increasing of additional β-Si3N4 particles in the magnetic field of 6 T, the degree of texture increased from 0.19 without seed particles to 0.76 with 9% (mass fraction) seed particles. The increase of seed particles content promoted the texture formation of Si3N4 ceramics.

The effect of static magnetic heat treatment on microstructures and mechanical properties of DZ483 alloy was investigated in combination with high temperature tensile experiments. It was found that the morphology of γ′ precipitates became spherical in the magnetic field of 12 T. Additionally, the application of magnetic field increased the tensile strength, elongation and micro-hardness of the superalloy. However, the magnetic field had no obvious effect on the reduction in area of alloys. The changes in microstructures could be attributed to the variation of the γ/γ′ lattice misfit and interfacial energy in the magnetic field.

The effect of a high magnetic field on the stray grains in cross-section change region was investigated experimentally during directional solidification of superalloy. The microstructures showed that the high magnetic field significantly suppressed the stray grains formation in cross-section change region. Meanwhile, the temperature curves indicated that the nucleation undercooling was significantly increased in a high magnetic field. The effect of a high magnetic field on the stray grains was discussed based on the nucleation mechanism.

The nucleation undercoolings of non-magnetic metals like paramagnetic aluminium in high magnetic fields were measured by the differential thermal analysis technique. It was shown that the nucleation undercooling of pure aluminium increased with increasing the magnetic field, while its melting temperature was hardly changed. Based on the model of magnetic dipoles at the interface, it is proposed that the magnetic-field-induced interfacial energy mainly contributes to the increase in undercooling. The change in undercooling in the magnetic field is calculated theoretically, which is in comparison with experimental data. Additionally, the inhibition of atom diffusion in the magnetic field plays a role in the change of undercooling.

The effect of a high magnetic field on the dendrite morphology of superalloy DZ417G during directional solidification at a low solidification velocity has been investigated experimentally. It was found that the magnetic field induces columnar to equiaxed transition (CET) and makes the primary dendrite arm spacing decrease. In addition, the magnetic field causes deformation of the solid–liquid interface shape and the macrosegregation in the mushy zone. Based on these results, it was found that both of the thermoelectric magnetic convection (TEMC) and the thermoelectric magnetic force (TEMF) cause CET, the change of solid–liquid interface shape and the formation of macrosegregation. This is in good agreement with predicted values of the TEMC and TEMF, respectively. The primary dendrite arm spacing was changed by the interdendritic TEMC in the magnetic field.

The contact angle (CA) goniometer adaptable to a superconducting magnet was developed based on the sessile drop method. The goniometer mainly consisted of the sampling system, the supporting system, and the image acquisition system. Some improvements were taken to avoid the effects of the magnetic field (MF) on the CA measurement. As an example, the CAs of water on two substrates of silica and polymethyl methacrylate (PMMA) were measured using the goniometer. The results with and without a MF showed a good repeatability and reliability. Additionally, the MF was found to reduce the CA of water, which probably stemmed from the change of the surface tension in the MF. The CA goniometer will become an important tool which is used to study the wettability of liquids on a solid in the MF.

International audience; Effect of static magnetic field on longitudinal macro segregation of primary silicon phase has been investigated in directionally solidified hypereutectic Al-Si alloy. Experimental and numerical simulation results indicate that the melt flow of Al-21 wt% Si alloy under magnetic field is the dominant factor leading to macro segregation of primary silicon phase. The intense melt flow, i.e., recirculation loops and microscopic flow, promotes solute Si to the mushy zone and sidewall of the crucible where the temperature is low and the primary silicon is more likely to precipitate, resulting in the formation of the U-shaped interface. The precipitated primary silicon tends to disappear during directional solidification, which induces the transition from the U-shaped interface to the planar interface. The increase of magnetic field intensity accelerates this transition process and increases the macro segregation. Furthermore, the freely drifted fine silicon particles in the bulk melt are transported to mushy zone by the forced flow, which contributes to macro segregation. This work facilitates the understanding of forced flow greatly changing the solidification structures of alloys under the magnetic field during directional solidification.

The magnetic field-assisted approach has been used in the synthesis of Co-doped SnO 2 diluted magnetic semiconductor nanocrystals. By annealing under the condition with or without magnetic field, 1D growth of the nanostructures can be induced, and the magnetic properties of the obtained nanocrystals are improved. Various techniques such as X-ray diffraction (XRD), transmission electron microscope (TEM), UV–visible spectrometry (UV–vis), Raman spectrometry and vibrating sample magnetometer (VSM) have been used to characterize the obtained products. The results show that the magnetic field holds important effects on the crystal growth of the Co-doped SnO 2 nanostructures, and improvement of magnetic properties. The intrinsic reasons are discussed.

The effect of magnetic field on the diffusion behavior of aluminum in Ni–Al alloy was investigated using diffusion couple technique. The results indicated that the diffusion of aluminum in the direction parallel to the magnetic field was suppressed and the frequency factor pertaining to the diffusion coefficient was decreased without much variation of the activation energy. The inhibition of diffusion with magnetic field was discussed based on the ambipolar diffusion theory.

The differential thermal analysis (DTA) apparatus has been designed in order to investigate the effect of magnetic fields on solid-melt phase transformation in pure bismuth. The endothermic peaks of DTA curves show that melting is insensitive to magnetic fields, which can be verified from thermodynamics. However, the exothermic peak obviously shifts to higher temperature as the magnetic field strength increases, from which the magnetic field does not affect the crystal growth but nucleation. On the basis of the assumption that there is an intermediate state between a crystal nucleus and a liquid atom, one possible reason for the shift of exothermic peaks is that kinetic barrier of nucleation is lowered and nucleation is activated by magnetic fields.

The high-magnetic-field tensiometer (HMFT) has been developed to measure surface tensions of liquids in high magnetic field based on the ring method. The HMFT was composed of three parts: weighing system, liquid circulatory system, and supporting system. Some improvements for the conventional tensiometer were made in order to overcome the magnetic effects. The surface tension of acetone was measured using the HMFT. The results showed that the surface tension of acetone linearly varied with the magnetic field intensity and increased by 0.69 mN m(-1) or 2.9% in the magnetic field of 10 T. The HMFT could better determine the surface tension of liquids with and without the magnetic field and it provided a simple and practical way to measure the surface tension of liquids at room temperature in a high magnetic field.

Objective: A system for real-time pyrosequencing by biolumino-metric assay coupled with a photodiode array is presented. The approach is based on the detection of DNA polymerase activity by an enzymatic luminometric inorganic pyrophosphate (PPi) detection assay. It is designed to offer a convenient pyrosequencing-based platform for DNA sequencing with low cost and simple structure. Method: Together with the automated dNTPs micro-dispensers, a photoelectric conversion circuit with high sensitive photodiode S1133-01 and ultra-low bias current monolithic operational amplifier OPA129 is chosen to detect the luminometric, monitoring the ATP production continuously. The signal to noise ratio is improved efficiently by routing PCB and shielding carefully. Results: A C14 standard light source is selected to compare the sensitivity of the system to the photomultiplier tubes (PMT). The results show that the magnification of the circuits is ten times higher than the PMT, which is sufficient for detecting the DNAs as small as 10 fmol. Four different type of dNTPs are injected into the reaction cell in turn and the peak of luminescence illuminates the result, which is coinciding with the commercial system. Conclusion: The system is small, simple and inexpensive, which is enough for real-time pyrosequencing. But there are many works to do to construct the fast and high-flux DNA sequencing system.