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Abstract: The thermal instability of the Fe fibers in the heavily deformed Cu–12.8wt.%Fe composites is investigated experimentally and numerically. The fiber evolution is characterized by a field emission scanning electron microscopy (FESEM). The results show that the dominant instability of the Fe fibers is the longitudinal boundary splitting which is determined by the greater cross sectional aspect ratio (width/thickness, w/t) and the larger ratio of boundary to interfacial energy (γ B/γ S). The longitudinal boundary splitting makes the ribbon-like Fe fibers evolve into a series of cylindrical fibers. Then the cylindrical Fe fibers undergo the instability process in terms of the breakup, growth and coarsening concurrently. The breakup times are accurately predicted by the Rayleigh perturbation model. The growth process primarily contributes to the higher increasing rate of the fiber radius during isothermal annealing at 700°C than that calculated by the coarsening theory developed for cylindrical fibers, since the Cu-matrix of composites is highly supersaturated after casting/cold-working process. [Copyright &y& Elsevier]

Abstract: With the imposition of a high magnetic field up to 11.5T, the morphologic transition of the MnBi phase and the magnetic properties of the Bi–4.36wt.% and 8.25wt.% Mn alloy specimens solidified from a semi-solid state were investigated. Compared with the irregular shape and unequal dimensions of MnBi grains under 0T, the coarsened MnBi grains were connected together and tended to be parallel to the direction of the external field of 11.5T. The changes might be attributed to the Ostwald ripening of ferromagnetic grains in the isothermal holding stage and subsequent aggregation along the direction of external field driven by mutual magnetic force among the grains. The uniform orientation of the ferromagnetic MnBi grains obtained in the microstructures effectively improves the saturation magnetization of the Bi/MnBi composite materials, but the oversized grains and the defects in grains make the coercivity decrease. [ABSTRACT FROM AUTHOR]

Abstract: The magnetic properties of Fe–49%Sn monotectic alloys were investigated after the alloys were solidified with and without a high magnetic field of 10T. The results showed that there was a significant difference between their hysteresis loops measured parallel and perpendicular to the applied high magnetic fields for the solidification process. Therefore, high magnetic fields applied in solidification process increased the magnetic anisotropy in the alloys. Along the parallel directions of the high magnetic field applied in their solidification process, the saturation magnetization M s, magnetic susceptibility dM/dH M and remanent magnetization of Fe–49%Sn monotectic alloys were increased obviously, which resulted from the improvement in the aligned microstructure of Fe–Sn alloys by applying the high magnetic field to the solidification process. A modified Stoner–Wohlfarth model was introduced to explain the experimental results. [Copyright &y& Elsevier]

Molecular dynamics simulation with the embedded atom method was applied to study the melting and coalescence in the mixed Cu-Ni nanoclusters. The validity of the model was tested by examining the consistency of the phase diagrams of the (CuNi) and (CuNi) clusters with the Cu-Ni bulk. The coalescences of two mixed Cu-Ni clusters and a pure Cu cluster with a pure Ni cluster were simulated. The coalesced temperature T forming a liquid complex and melting temperature T of the cluster with the same size were compared. The results indicate that T is higher than T for the coalescences of both (CuNi) and (CuNi) clusters. The analysis of the relationship between the Cu-Ni bond content and T indicates that the formation of the Cu-Ni bonds contributes a lot to the phenomenon. [ABSTRACT FROM AUTHOR]

Abstract: Mn–89.7wt.%Sb alloy specimens were solidified in various magnetic fields with different holding times. The influence of the high magnetic field on the orientation of both the primary and eutectic MnSb crystals and on the alignment of the primary MnSb grains in the alloys has been investigated. It was found that the primary MnSb crystals were oriented with their c-plane parallel to the imposed magnetic field direction, but the eutectic MnSb from a eutectic MnSb alloy could not be oriented by the high magnetic field. The primary MnSb dendrites were aligned along the magnetic field direction. This alignment may be attributed to combined effects of crystal orientation, crystal growth feature and heat flow. [Copyright &y& Elsevier]

Abstract: The melting points of bulk Cu–Ni over the complete range of compositions were simulated by a model of molecular dynamics with general embedded atom method (EAM). The melting point of bimetallic Cu–Ni clusters was also studied by using the same model. The results show that the changing trend of the simulated melting points for the bulk Cu–Ni agrees with the experimental phase diagram very well. The melting point of the cluster increases with the increase of Ni composition and the increasing trend agrees well with the theoretical phase diagram of bimetallic nanoparticles. The melting point of the cluster is higher than those of clusters without segregation and composition-dependent because the segregation of Cu atoms decreases the melting point. The simulation for the size-dependent melting points of the clusters with 20%, 50%, and 80% Ni shows a linear relation between the inverse cluster sizes and the melting points. The linear relation is not affected by the segregation. [Copyright &y& Elsevier]

Abstract: The effects of high magnetic fields on the migration and rotation of TiAl3 particles in an Al–7wt.% Si alloy were studied. Without magnetic fields, the rod-like TiAl3 particles segregate at the lower part of the solidified structure. Under high uniform magnetic fields, these particles rotate to an orientation with their longitudinal axes parallel to the direction of the magnetic flux. The segregation of the particles reduces with the increase of the magnetic flux density. A negative gradient field enhances the effect of the uniform magnetic field. By altering high magnetic fields, Al–Si alloy samples containing homogeneously distributed and preferably aligned TiAl3 particles were prepared. [Copyright &y& Elsevier]

Abstract: The effects of high magnetic fields on the as-cast microstructure and grain boundaries of binary Al–Li alloy were investigated. It was found that secondary dendrite arm spacing (SDAS) decreased and the distribution of the SDAS became uniform under high magnetic fields. The application of a high magnetic field had no effect on the type of precipitated phases in the alloy, although δ′ (Al3Li) precipitates coarsened under the field of 11.5T. Area fraction of grain boundary (AFGB) slightly decreased at first and then increased with increasing magnetic flux density under uniform magnetic fields, while it decreased under magnetic field gradients. [Copyright &y& Elsevier]

Abstract: Solidification experiments of aluminum–nickel binary alloys under uniform high magnetic fields have been conducted. The effects of high magnetic fields on the crystal orientation of Al3Ni were investigated by XRD and the alignment of primary phases Al3Ni were also analyzed. Experimental results showed that the easy magnetization axis of Al3Ni crystal oriented parallel to the imposed magnetic fields and the primary phase Al3Ni aligned perpendicular to the magnetic fields. Magnetic orientation of crystal was determined by magnetic anisotropy energy. Whereas the phase alignment should be contributed to the combined effects of magnetic orientation, crystal growth and the effects of magnetic fields on mass transport during solidification. [Copyright &y& Elsevier]

MnSb/Sb–MnSb functionally graded material (FGM) has been successfully fabricated using a semi-solid forming process under magnetic field gradients. Mn–Sb alloy with a hypoeutectic composition was used to produce particle-dispersed composites. The graded composition of MnSb particles could be controlled by adjusting the BdB/dz value of the field gradient and the holding time. The direction along which the volume fraction of the particles increased could also be controlled artificially by adjusting the field gradient direction. [Copyright &y& Elsevier]

Bulk layered synthetic Mn–Sb composites, with a gradient structure in morphology and composition towards the surfaces, were fabricated directly in situ under high magnetic field gradient conditions. Both of the primary phases of Mn–Sb binary system, i.e. MnSb and Sb, were found to segregate simultaneously from desired domains with a gradient interface in morphology in those alloys with hypo-eutectic composition. The volume fraction of the segregated phases strongly depended on the product of the magnetic flux density and its gradient. [Copyright &y& Elsevier]

Abstract: The effects of magnetic field on nucleation barrier of the phase transformation from austenite to ferrite at different cooling rates in 42CrMo steel have been investigated. The microstructures of ferrite and pearlite aligned along the magnetic field direction (parallel to the hot-rolling direction) are obtained at a cooling rate of 10°C/min, resulting from the kinetic effects of the applied magnetic field during cooling and the microstructural influences of an inhomogeneous deformation occurring during the previous hot rolling. In this case, the formation of ferrite grains at higher temperatures is attributed mainly to the preferential nucleation at austenite boundaries. However, a fairly uniform microstructure of randomly distributed ferrite and pearlite is formed at a high cooling rate of 46°C/min in the magnetic field of 14T, as a result of both intergranular and intragranular nucleation at relatively low temperatures. Probing into this issue is helpful to gain a better understanding of kinetic influences of magnetic field on the phase transformation from austenite to ferrite. [Copyright &y& Elsevier]

Abstract: The effects of high magnetic field annealing on the interdiffusion of Co/Ni bilayer films were investigated in this paper. A clear CoNi alloying zone can be observed by field emission scanning electron microscopy and energy dispersive spectroscopy, for samples annealed with and without magnetic field. Significant Co and Ni interdiffusion was verified by X-ray photoelectron spectroscopy. Based on the thickness of the diffusion layer, the distribution of atoms and the microstructure of interfacial products, the interdiffusion coefficients of the bilayer diffusion couples were calculated. Compared with the no-field case, the interdiffusion coefficient clearly increased when a high magnetic field of 12T was applied. This effect can be attributed to an increase in the chemical potential gradient induced by magnetic free energy in a high magnetic field. [Copyright &y& Elsevier]

Abstract: This paper studies the freezing of Co clusters with diameters ranging from 2.52 to 4.62nm by using molecular dynamics simulation with an embedded atom method. It was found that the frozen structures are closely related to cluster sizes. When the cluster size is small (≤2.94nm), an icosahedron is formed. When the cluster size is large (≥3.79nm), an hcp bulk-like structure is formed. If the cluster size is 3.37nm, a decahedron is formed. It was also found that the frozen structure is strongly dependent on the energy of geometric shapes at given sizes. The size-dependent frozen structures of clusters provide a new method for fabricating novel materials with nano microstructures. [Copyright &y& Elsevier]