Woven carbon fibers reinforced Al–Mg (95–5 wt%) matrix composites were successfully prepared by an electromagnetic casting method. In order to improve the wetting behavior, different stabilizers were respectively used in the electroless plating process to coat the fibers with a better Ni/P layer. The lactic acid offered the most outstanding stabilizing effect. The casting results indicated that the contact time between the molten metal and the carbon fibers was vital to the bonding degree: increasing the solidification time significantly reduced the cavity defects which located near the interface; however, an overly long solidification time would result in a tendency to crack in the centers of the woven fibers. The hot-pressing treatment with optimum parameters significantly mitigated the crack and cavity defects which are common in the composite prepared through casting method. The appropriate applied compression ratio turned out to be approximately 6%. Three point bending test showed that the bending strength of the composite had an improvement for 33.6% than that of Al-alloy matrix.

Iron is generally regarded as an unavoidable impurity in Al-Si casting alloys. The acicular Al3Fe and β-Al5FeSi (or Al9Si2Fe2) are common iron-containing intermetallic compounds (IMCs) in conventional structure which have a detrimental impact on the mechanical properties. In this paper, ultrasonic field (USF) was applied to modify acicular iron phases in Al-12%Si-2%Fe and Al-2%Fe alloys. The results show that the USF applied to Al-Fe alloys caused the morphological transformation of both primary and eutectic Al3Fe from acicular to blocky and granular without changes in their composition. In the case of Al-Si-Fe alloys, ultrasonic treatment led to both morphological and compositional conversion of the ternary iron IMCs. When the USF was applied, the acicular β-Al9Si2Fe2 was substituted by star-like α-Al12Si2Fe3. The modification rate of both binary and ternary iron IMCs relates to the USF treatment duration. The undercooling induced by the ultrasonic vibration contributes to the nucleation of intermetallics and can explain the transformation effect.

•The woven carbon fibers reinforced Al-matrix composites were successfully prepared by a casting process.•The optimization of the technological parameters and the combination mechanism were discovered.•The segregation phenomenon of elements had been properly explained by the mixing enthalpy theory.Woven carbon fibers reinforced Al–Mg (95–5 wt%) matrix composites are successfully prepared through an electromagnetic casting process. The Ni/P coating is obtained using an electroless plating method to offer a better wettability in the casting. The appropriate pre-heating temperature of reinforcement is determined to be 600 K, and the molten matrix temperature should be controlled at approximately, 1013 K. Due to the presence of Ni/P coating, the infiltrated metal is able to spread out on the fiber surface readily. Finally, the accumulation of the metal on the fibers eventually fills all interspaces in the woven fibers. The addition of Mg shows a beneficial effect during the casting process by transferring itself into the coating more readily than Al and by segregating closely around the fibers, which effectively limits the formation of the Al4C3 brittle phase. The mixing enthalpy theory is introduced to explain the distribution of elements in this composite.

Copper–chromium matrix composites reinforced by TiB2 particles were prepared by in situ reaction between titanium and copper–boron alloy in the melt. The microstructures, mechanical, and electrical properties of the composite were investigated under as-cast and aging conditions. The results indicate that the TiB2 particles are formed by in situ reaction in matrix. The addition of TiB2 in composite reduces the segregation degree of Cr particles in matrix and inhibits the coarsening of Cr particles at high aging temperature. High hardness of Cu–Cr–TiB2 composite is achieved due to the multiple hardening mechanisms, which are in situ TiB2 particles hardening and precipitation hardening from Cr particles. The wear resistance of composite presents a dramatic improvement due to the formation of TiB2 particles, and TiB2 particles have significant effect on wear mechanism of Cu–Cr–TiB2 composite. The conductivity of composite is lower than that of Cu–Cr alloy, which is attributed to higher resistivity of TiB2 particles and the incremental interface scattering caused by TiB2 particles. But the composites with high TiB2 content still have considerable conductivity after aging.

•3003/4045 clad hollow billet was fabricated by horizontal continuous casting.•Metallurgical bond occurs during the solidification due to diffusions of Si and Mn.•The shear strength of the interface is higher than that of the 3003 alloy.•Incompatible deformation between 3003 and 4045 occurs during rolling processes.The 3003/4045 clad hollow billets are prepared in the present study. Microstructures, solute distribution and bonding strength of the interfacial regions were investigated. The effects of plastic deformation on the evolution of microstructure and microhardness of the interfaces were also studied. The results show that metallurgical bonding between the solid and liquid Al alloys can be obtained with optimal parameters. Si and Mn atoms diffuse across the interface to form a diffusion layer with the thickness about 30 μm on average. The mean tensile-shear strength of as-cast clad hollow billet is 85.3 ± 9.2 MPa, and the strength of the interface is higher than that of 3003 alloy. Incompatible deformation between 3003 and 4045 layers occurs during rolling processes, and the needle-like Si phase transforms to the dispersive particles. The gradient distribution of microhardness across the interface is retained after the deformation.

An innovative direct chill casting process to prepare Al–10 wt%Si and Al–1 wt%Mn alloy circular clad ingots has been developed in the present study. The experimental casting parameters were determined by theoretical analysis, numerical simulation and experimental processes. The interface of clad ingots was investigated by methods of metallographic examination, electron probe microanalysis (EPMA) and transmission electron microscopy (TEM). The results showed that excellent metallurgical bonding of two different aluminum alloys could be achieved by direct chill casting. The Al–1Mn alloy which was poured into the mold earlier served as the substrate for heterogeneous nucleation of Al–10Si alloy. Because of diffusion of Si and Mn elements, a diffusion layer with a thickness of about 40 μm on average between the Al–10Si and Al–1Mn alloys could be obtained. The tensile strength of the clad ingot was 106.8 MPa and the fractured position was located in the Al–1Mn alloy side, indicating the strength of the interfacial region is higher than that of Al–1Mn alloy.

Purifying of metallurgical grade silicon through electron beam melting is a method used to provide high-purity material. In this research, the influence of refining temperature, refining time, electron beam power and feed rate on refining effectiveness are studied. With the improvement of refining temperature, saturated vapor pressure of each impurity element increase quickly, but at the same time the evaporation of the silicon increase. Refining temperature is 2773 K in order to improve the removal of the impurity. In order to make the impurity content decrease by one order of magnitude, the refining time should be 3 h. Through the calculation of electron beam energy, the relationship between melting temperature, electron beam melting power and refining time is calculated. According to the fitting equation of feed rate, silicon ingot coefficient and refining time, feed rate can be calculated from processing parameters. In this research, impurities can be removed effectively through electron beam melting and twice directional solidification. Most industrial silicon impurities can be removed below 10 ppmw, and the concentration of some impurities are even lower than 1 ppmw.Highlights► Electron beam melting is a method used to provide high-purity material. ► Refining parameters are refining temperature, refining time, electron beam power and feed rate. ► Most impurities can be removed below 10 ppmw, some are even lower than 1 ppmw.

•The acicular β-AlSiFe phase was replaced by α-AlSiFewith ultrasound at 720 °C.•The acicular β-AlSiFe was fractured when power ultrasound was applied at 610 °C.•The transformation is ascribed to the cavitation nucleation and failure mechanisms.In general, the iron impurity is detrimental to the mechanical properties of Al–Si alloys. The α-phase and β-phase are the most important and common iron-containing intermetallic compounds (IMCs) in Al–Si alloys. During conventional casting, the acicular β-phase is stable, and considered to be harmful. In this paper, the Al-12%Si-2%Fe alloy was treated by power ultrasound and solidified under different cooling conditions. The effects of ultrasonic treatment (UST) and cooling rate on morphology and composition of IMCs were investigated. The results showed that UST can change the morphology and composition of iron-containing IMCs and promote the formation of metastable α-phase. When the ultrasound was applied at 720 °C, the amount of starlike α-phase increases and the acicular β-phase decreases with increasing applied time of UST. In addition, the polygonal α-phase is formed and substitutes for the β-phase when quenching after UST for 60 s and 120 s, suggesting that the formation of β-phase can be suppressed under this condition. For the case of UST at 610 °C which the β-phase has been nucleated, the β-phase transforms from an acicular shape to the rod-like morphology, indicating that the cavitation-induced fracture of β-phase.

The Al–10%Si alloy and Al–1%Mn alloy bimetal slabs are prepared by continuous casting. The microstructures around the interface are investigated, chemical composition distributions across the interface are detected, and tensile strengths are evaluated at the top, center and bottom regions of the bimetal slab. The results show that the Al–1%Mn alloy serves as a substrate of heterogeneous nucleation of Al–10%Si alloy at the bimetal interface. The metallurgical bonding is excellent without any discontinuities along the interface due to the diffusions of Si and Mn elements. The thickness of diffusion layers is about 40 μm on average. The tensile strengths of the top, center and bottom regions of the bimetal slab tend to be uniform.Highlights► The bimetal slab consisting of Al–10%Si alloy and Al–1%Mn is produced by cast. ► Metallurgical bond occurs during the solidification due to diffusions of Si and Mn. ► The thickness of the diffusion layer of the bimetal slab is about 40 μm. ► Al–1%Mn alloy serves as the substrate for heterogeneous nucleation of Al–10%Si alloy.

Rotating magnetic field is introduced in the production process of Ni–Al precursor alloy of skeletal Ni catalyst. The results showed that the big dendrites of Al3Ni2 disappeared, the size of Al3Ni2 decreased from 64.5 μm to 37.2 and 35.5 μm, phase content of Al3Ni2 decreased while Al3Ni increased after applying field current of 80 A and 140 A, respectively. The change of phase content is probably caused by the increase of surface area between the Al3Ni2 phase and fluid which is favorable to the peritectic reaction.Research highlights► We report the effect of rotating magnetic field on the structure of Al–Ni peritectic alloy. ► Big dendrites of Al3Ni2 disappeared, and Al3Ni2 was finely divided in the alloy. ► Phase content of Al3Ni2 decreased while Al3Ni increased. ► Electromagnetic stirring is favorable to the peritectic reaction.

The purpose of this paper is to study large-sized copper billets refined with 5N ultrahigh purity after vacuum melting and directional solidification (VMDS). The precise impurity analysis of copper billets was carried out with a glow discharge mass spectrometer (GDMS). The results demonstrate that the total concentration of twenty-two impurities is decreased by 63.1wt.%–66.5 wt.%. Ag, P, S, Na, Mg, Se, Zn, In and Bi are easy to be removed due to lgPimp - lgPCu > 1.5, and they can be removed effectively under the vacuum condition of 1650–1700 K for 30 min. The electrical conductivity of 5N copper is higher than that of the raw material as the impurity concentrations decrease. The segregation effect in directional solidification can be remarkable when the equilibrium distribution coefficient (k0) value is less than 0.65 due to the strong affinity of Cu for some metallic and non-metallic impurities.

Rotating magnetic field (RMF) of commercial frequency is used in pilot scale of horizontal continuous casting of CuNi10Fe1Mn alloy hollow billets. The effect of RMF on solidification macrostructure, element distribution and mechanical properties is studied. The result shows that the formerly inhomogeneous columnar grain macrostructure turns into homogeneous equiaxed grain macrostructure with the application of RMF, the average grain size reduces from 6.1 to 0.56 mm and the element segregation is restrained, the ultimate tensile strength is increased by 20.3% and the elongation is improved by 65.7% compared to those without RMF. Moreover, the action mechanism of RMF is discussed to explain its effect on improving the solidification macrostructure, element distribution and mechanical properties.

Alternating magnetic field of commercial frequency was used during horizontal continuous casting of copper hollow billets. The effects of input current intensity of alternating magnetic field and casting parameters were studied to obtain good quality production. The result shows that the formerly unhomogeneous columnar grain structure turns into homogeneous equiaxed grain structure with the application of alternating magnetic field. Different casting parameters such as casting speed, casting temperature and cooling intensity are attempted to explore best techniques to match with the effect of alternating magnetic field. When the input current intensity is 50 A, casting speed is 0.0042 m/s, casting temperature is 1150 °C and cooling intensity is 1m3/h, the tensile strength is increased by 15.9% and the elongation is improved by 63.8% compared to those without alternating magnetic field.

A novel approach, was designed to obtain thixotropic structure of equiaxed or non-dendrtic grains for rheocasting, and demonstrated experimentally using A356 aluminum alloy. The circumstance in bulk liquid metal, which would burst into copious nucleation, and at the same time create homogeneous distribution of temperature and solute, was constructed by combined utilization of rotating magnetic fields and a cooling tube. Both the solidified microstructures in metal mold and sand mold exhibited non-dendritic characteristic. Analyses of the rheocasting A356 microstructure indicated that high density of nuclei occurred by inserting a cooling tube into rotating slurry at liquidus temperature. In the case of slow cooling rate, mushy slurry obtained with high nuclei density kept non-dendritic morphology of primary particles with holding time, accompanying grain particles’ coarsening and spheroidizing; moreover, the eutectic silicon got coarsening with retaining time.

The effects of the particle size of ground metallurgical grade silicon (MG-Si), the sort of acids, and the type of stirring on the purified efficiency of MG-Si were investigated. It was found that a particle size less than 0.1 mm was most effective for acid leaching; the extraction yield of impurities was increased by 9% with HF leaching compared with HCl leaching and HNO3 leaching, and increased by 7% with ultrasonic stirring compared with mechanical stirring. The principle of hydrometallurgical purification of metallurgical grade silicon under ultrasonic fields was also discussed.

AZ91 magnesium alloy was rheoformed using rotating magnetic fields (RMFs) after isothermal near-liquidus treatment. Thixotropic microstructures obtained at different temperatures were characterized in detail and linked to the corresponding volume solid fraction, and serial sectioning experiments were performed to construct three-dimensional morphologies of clusters consisting of conglutinated primary grains. The experimental results indicated that incompact structure agglomerating a few primary solid particles was observed within structures of low solid fraction, while a reduction in the castings’ forming temperature and so increasing the fraction of primary solid phase brought out interaction among the primary particles within vigorously stirring melt, and thus caused slide and plastic deformation between or among the neighboring solid particles. In contrast with structure with low solid fraction, this slide and plastic deformation resulted in differently morphological 3D structures welded together with much more solid particles. Moreover, the increase in solid fraction mainly lied on the formation of new particles.

Using first-principles methods, we have performed a systematic investigation of the cubic, rhombohedral and hexagonal diamond polytypes, both in equilibrium and under hydrostatic pressure. For each of the diamond polytypes (2H, 3C, 4H, 6H, 8H, 9R, 10H-SiC form, 10H-ZnS form, 15R and 21R), the structural, energetic, and electronic properties are investigated. The calculated lattice parameters, mass densities and ground-state energies of the diamond polytypes show clear trends with their hexagonality, while bulk modulus and elastic parameters are rather insensitive to the hexagonality. It is found that there are no phase transitions between these diamond polytypes studied in this work, at a pressure range from 0 to 500 GPa. For the series of diamond polytypes studied, the calculated results indicate that the relationship between ground-state electronic band gap and hexagonality at zero pressure is different from that observed at the hydrostatic pressure of 500 GPa.

Rotating magnetic field (RMF) is used in horizontal continuous casting of CuNi10Fe1Mn alloy hollow billets. The result shows that the formerly inhomogeneous columnar grain macrostructure turns into homogeneous equiaxed grain with the application of RMF. The microstructure without RMF transforms from coarse and disordered dendrites to dense dendrites which have obvious orientation, while the microstructure with RMF from center to edge displays the evolution from spherical grains to disordered dendrites without orientation. The mechanical properties are improved remarkably.

Diamond is the hardest material with superior mechanical stability. Due to the widespread application in high pressure research, stability limit of diamond at ultrahigh pressure is an importance issue for theoretical and experimental studies, which remains controversy between theoretical prediction and experimental observations. In this paper, we report first-principle calculations on the relative stability of diamond under non-hydrostatic compression and the computational results demonstrate that the cubic diamond would become unstable with respect to the lonsdalite under isotropic stress tensor with mean stress as low as 26 GPa, while agree well with experimental findings under similar non-hydrostatic loading conditions.

The structural properties, heat of formation, elastic properties, and electronic structures of six kinds of binary Al–Ru intermetallics were studied using first-principle calculations. The structural properties of these intermetallic compounds agree well with previously reported experimental data except that the computed equilibrium lattice parameters of the orthorhombic Al5Ru2 crystal (Cmcm) are significantly different from the experimental data reported by Mi et al. [Intermetallics 2003;11:643]. With increasing Ru concentration, the bulk modulus of Al–Ru intermetallics increases linearly. Most of the Al–Ru alloys considered are conductors, while the Al2Ru alloy is an indirect band gap semiconductor with a band gap of 0.168 eV.

High entropy alloys (HEAs) usually possess weak liquidity and castability, and considerable compositional inhomogeneity, mainly because they contain multiple elements with high concentrations. As a result, large-scale production of HEAs by casting is limited. To address the issue, the concept of eutectic high entropy alloys (EHEAs) was proposed, which has led to some promise in achieving good quality industrial scale HEAs ingots, and more importantly also good mechanical properties. In the practical large-scale casting, the actual composition of designed EHEAs could potentially deviate from the eutectic composition. The influence of such deviation on mechanical properties of EHEAs is important for industrial production, which constitutes the topic of the current work. Here we prepared industrial-scale HEAs ingots near the eutectic composition: hypoeutectic alloy, eutectic alloy and hypereutectic alloy. Our results showed that the deviation from eutectic composition does not significantly affect the mechanical properties, castability and the good mechanical properties of EHEAs can be achieved in a wide compositional range, and at both room and cryogenic temperatures. Our results suggested that EHEAs with simultaneous high strength and high ductility, and good liquidity and castability can be readily adapted to large-scale industrial production. The deformation behavior and microstructure evolution of the eutectic and near-eutectic HEAs were thoroughly studied using a combination of techniques, including strain measurement by digital image correlation, in-situ synchrotron X-ray diffraction, and transmission electron microscopy. The wavy strain distribution and the therefore resulted delay of necking in EHEAs were reported for the first time.