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Cu−0.5wt.%Cr alloy with high strength and high conductivity was processed by cryorolling (CR) and room temperature rolling (RTR), respectively. The microstructure, mechanical property and electrical conductivity of Cu−0.5Cr alloy after CR/RTR and aging treatment were investigated. The results indicate that obvious dislocation entanglement can be observed in matrix of CR alloy. The Cr particles in the alloy after CR and aging treatment possess finer particle size and exhibit dispersive distribution. The peak hardness of CR alloy is HV 167.4, significantly higher than that of RTR alloy. The optimum mechanical property of CR alloy is obtained after aging at 450 °C for 120 min. The conductivity of CR Cu−0.5Cr alloy reaches 92.5% IACS after aging at 450 °C for 120 min, which is slightly higher than that of RTR alloy.

Hot corrosion rates of Super 304H austenitic stainless steel pre-coated in Na2SO4–25%NaCl mixture salt film in air at 650 °C and 750 °C have been investigated by corrosion kinetics curves. The corrosion products are examined by means of X-ray diffraction and scanning electron microscopy coupled with energy-dispersive spectrometer, and electron probe micro-analyzer to analyze the scale structure and element distribution of the cross section. The results indicate that the kinetics curves are similar and display parabolic growth, and the mass gain obviously increases with the increasing temperature. A two-layer oxide scale composed of Fe oxides containing CuFe2O4 and Cr2O3 forms on the surface of the alloy and easily exfoliates with extending corrosion time or with improving corrosion temperature. Moreover, a corrosion-affected zone with micropores and micro-cracks appears beneath the oxide scale. It is concluded that the selective oxidation occurs and a protective oxide scale forms at the early corrosion stage. The melt salts destroy the integrity of the oxide scale and accelerate hot corrosion of the alloy by the cyclical oxidation–chlorination during the further corrosion processing. In addition, internal sulfidation also contributes to the corrosion of the alloy.

Three-layer 6009/7050/6009 aluminum alloy clad slab was fabricated by an innovative direct-chill casting process. To study the response of the clad slab to plastic deformation and heat treatments, homogenization annealing, hot rolling, solution and aging were successively performed on the as-cast 6009/7050/6009 clad samples. The results revealed that excellent metallurgical bonding between 7050 alloy layer and 6009 alloy layer was achieved under optimal parameters. The clad ratio obviously decreased when the annealed sample was rolled to 55% hot reduction level, and then changed slightly with further rolling. Furthermore, the content of rodlike Zn-rich phases increased significantly in 7050 alloy layer in the homogenized clad samples after rolling at 55%, 65% and 75% hot reduction levels, and the higher level of hot reduction resulted in narrower diffusion layer. Subsequent solution and aging significantly improved the hardness in 7050 alloy layer, interfaces and 6009 alloy layers of the rolled samples except for the thin side for the 75% hot reduction sample.

A series of CoCrFeNb x Ni ( x values in molar ratio, x = 0, 0.25, 0.45, 0.5, 0.75, 1.0 and 1.2) high entropy alloys (HEAs) was prepared to investigate the alloying effect of Nb on the microstructures and mechanical properties. The results indicate that the prepared CoCrFeNb x Ni ( x > 0) HEAs consist of a simple FCC solid solution phase and a Laves phase. The microstructures of the alloys change from an initial single-phase FCC solid solution structure ( x = 0) to a hypoeutectic microstructure ( x = 0.25), then to a full eutectic microstructure ( x = 0.45) and finally to a hypereutectic microstructure (0.5 x x = 0.45) alloy with a full eutectic microstructure possesses the highest compressive fracture strength of 2558 MPa and a fracture strain of 27.9%. The CoCrFeNi alloy exhibits an excellent compressive ductility, which can reach 50% height reduction without fracture. The Nb0.25 alloy with a hypoeutectic structure exhibits a larger plastic strain of 34.8%. With the increase of Nb content, increased hard/brittle Laves phase leads to a decrease of the plasticity and increases of the Vickers hardness and the wear resistance. The wear mass loss, width and depth of wear scar of the Nb1.2 ( x = 1.2) alloy with a hypereutectic structure are the lowest among all alloy systems, indicating that the wear resistance of the Nb1.2 alloy is the best one.

Semisolid-rolling method was successfully developed to prepare the Ni-coated woven carbon fibers reinforced Al-matrix composite. Due to the appropriate matrix flowability and rolling pressure, the Al-matrix could infiltrate into the woven fibers sufficiently and attach to the reinforcements closely forming a smooth interface. The rolling speed of 4 rad/min offered a subtle equilibrium between the heat transfer and the material deformation. The covering matrix should be controlled at semisolid state to provide a better infiltration behavior and a protective effect on the carbon fibers. With the addition of fibers, an improvement for more than 25% was obtained in the bending strength of the materials. Furthermore, the woven carbon fibers could strengthen the composite in multiple directions, rather than only along the fiber longitudinal directions. The annealing process promoted the Ni coating to react with and to diffuse into the matrix, resulted in an obvious increase of the bending strength.

6009/7050 alloy bimetal slab was prepared by a direct-chill (DC) casting process. Homogenizing annealing, hot rolling and T6 treatment were successively performed and their effects on microstructure and properties of the slab were studied. The results reveal that the average diffusion layer thickness of as-cast slab, determined by interdiffusion of elements Zn, Cu, Mg and Si, was about 400 µm. Excellent metallurgical bonding was achieved because all tensile samples fractured on the softer 6009 alloy side after homogenizing annealing. After homogenizing annealing plus rolling, the average diffusion layer thickness decreased to 100 µm, while the network structure of 7050 alloy side transformed to dispersive nubby structure. Furthermore, subsequent T6 treatment resulted in diffusion layer thickness up to 200 µm and an obvious increase of the Vickers hardness for both 7050 and 6009 sides. The layered structure of the as-cast 6009/7050 bimetal is retained after hot rolling and T6 treatment.

The influences of slight amount of B element on the microstructure and properties of AlCoCrFeNiBx high entropy alloys (x = 0, 0.01,…, 0.09 and 0.1, mole fraction) were investigated. The AlCoCrFeNi high entropy alloy exhibits equiaxed grain structures with obvious composition segregation. However, with the addition of B element, the alloys exhibit dendrite structures. Inside the dendrites, spinodal decomposition structure can be clearly observed. With the addition of B element, the crystal structures change from (B2 + BCC) to (B2 + BCC + FCC) structures, and the hardness firstly increases from HV 486.7 to HV 502.4, then declines to HV 460.7 (x ≥ 0.02). The compressive fracture strength firstly shows a trend of increasing, and then declining (x ≥ 0.08). The coercive forces and the specific saturation magnetizations of the alloys decrease as B addition contents increase, the decreasing coercive forces show a better soft magnetic behavior.

In order to study the wear behavior of different kinds of contact wires, the dry sliding wear behaviors of Cu–Sn, Cu–Ag and Cu–Mg alloys prepared by up-drawn continuous casting and followed continuous extrusion were studied. The research was tested on a block-on-ring wear tester. The results indicate that the friction coefficient is remarkably influenced by the formation of a continuous tribofilm, which consists of oxidation film. The abrasion, adhesion, oxidation and plastic deformation are observed. Oxidation and abrasion wear mechanisms dominate at the lower sliding velocity and load. The combination of oxidation and adhesion play leading roles with the increasing load and velocity. Plastic deformation is detected under higher applied load and sliding velocities.

A nickel-based coating was deposited on the pure Al substrate by immersion plating, and the Al/Cu bimetals were prepared by diffusion bonding in the temperature range of 450–550 °C. The interface microstructure and fracture surface of Al/Cu joints were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The mechanical properties of the Al/Cu bimetals were measured by tensile shear and microhardness tests. The results show that the Ni interlayer can effectively eliminate the formation of Al-Cu intermetallic compounds. The Al/Ni interface consists of the Al 3 Ni and Al 3 Ni 2 phases, while it is Ni-Cu solid solution at the Ni/Cu interface. The tensile shear strength of the joints is improved by the addition of Ni interlayer. The joint with Ni interlayer annealed at 500 °C exhibits a maximum value of tensile shear strength of 34.7 MPa.

The combined effects of direct current pulsed magnetic field (DC-PMF) and inoculation on pure aluminum were investigated, the grain refinement behavior of DC-PMF and inoculation was discussed. The experimental results indicate that the solidification micro structure of pure aluminum can be greatly refined under DC-PMF. Refinement of pure aluminum is attributed to electromagnetic undercooling and forced convection caused by DC-PMF. With single DC-PMF, the grain size in the equiaxed zone is uneven. However, under DC-PMF, by adding 0.05% (mass fraction) Al–5Ti–B, the grain size of the sample is smaller, and the size distribution is more uniform than that of single DC-PMF. Furthermore, under the combination of DC-PMF and inoculation, with the increase of output current, the grain size is further reduced. When the output current increases to 100 A, the average grain size can decrease to 113 μm.

Multi-elements alloy with good thermal stability is expected to serve as the superheater tube material of ultra-supercritical boiler and may suffer from hot corrosion under the coal-fired atmosphere. In this study, the corrosion resistance behavior of multi-elements alloy CoCrFeNiTi0.5 coated with alkali metal sulfates at 750°C is investigated systematically. The results showed the corrosion kinetics curves of the alloy followed a parabolic growth rate. The corrosion products, which consisted of volatile Na (CrO4) (SO4), (Fe,Ni) xSy, Cr/Ti oxide as well as compound oxides with spinel structure AB2O4, were found in the oxide scale and internal attack zone of the alloy. The oxide layer had good adhesion with the matrix at the beginning of corrosion. Prolonging corrosion time, the oxide layer in thickness increased and became loose as well as porous. The micro-pores generated in the interface between the oxide scale and matrix with the occurrence of the internal oxidation and internal sulfidation. In a word, the corrosion resistance behavior of multi-elements alloy CoCrFeNiTi0.5 at 750°C can be attributed to the formation of the protective oxide layers and to the basic fluxing in molten Na4SO4 induced by low melting point eutectic.

At the late stage of solidification with ultrasonic treatment (UST) in Al-Si alloys, a part of semisolid overflows and climbs along the probe. The interesting phenomenon and its influence on the solidification microstructure were investigated in order to better study the mechanism of UST. It is considered that the overflowing phenomenon occurs due to the changes of vibration and flow in the remaining semisolid. Because the overflowed portion comes from the region with intense UST effect and vibrates with the probe during solidification, great modification of primary and eutectic Si (about 10 μm in length) and refinement of primary α(Al) (about 70 μm in size) are observed in this portion.

In order to improve the quality of clad ingots, diverse physical fields including electromagnetic stirring, power ultrasonic and compound field of ultrasonic and electromagnetic stirring were attempted to prepare clad ingots of 3003/4004 alloys. The solidification structures near the interface in clad ingots were investigated. The experiment results indicate that the solidification structure of 4004 alloy changes from dendritic crystals to petal-like grains when the clad ingot is treated by electromagnetic stirring. With the effect of power ultrasonic, the solidified microstructure of 4004 alloy exhibits the refinement of both primary α(Al) and eutectic silicon. Under the compound field, the primary α(Al) is refined, the morphology of eutectic silicon has a transition from a coarse plate-like form without treatment or thin acicular-like form with power ultrasonic to fine coral-like form.

A new purification process was developed to remove impurities in metallurgical grade silicon (MG-Si) by electromagnetic induction slag melting (EISM). Vacuum melting furnace was used to purify boron in different slag systems. The results show that the removal effect in SiO2-CaO-Al2O3 systems is better than that in other slag systems by EISM. The boron content in MG-Si is successfully reduced from 1.5×10−5 to 0.2×10−5 during EISM at 1 823 K for 2 h. Meanwhile, Al, Ca and Mg elements in MG-Si are also well removed and their removal efficiencies reach 85.0%, 50.2% and 66.7%, respectively, which indicates that EISM is very effective to remove boron and metal impurities in silicon.

The maximum undercooling up to 550 K was achieved in the bulk eutectic Ni 78.6 Si 21.4 alloy melt through glass fluxing, which was combined with cyclic superheating. Transmission electron microscope (TEM), scanning electron microscope (SEM) and optical microscopy techniques were adopted to investigate the microstructure, and identified the phase composition. The directional growth, quasi-regular and refined microcrystalline microstructures were achieved in the as-solidified structure with the increased undercooling. With the increase of undercooling, the relationship between the microstructure and the hardness including the size effect of crystal grain were systematically investigated. The experimental results show that directional growth, quasi-regular and refined microstructure produced large strengthening effect, and improved the hardness to 56.5 on the Rockwell hardness C (HRC) scale. The fact is also proved by the Vickers hardness.

The effects of separation time and magnetic induction intensity on the separation efficiency of alumina particles with diameters varying from 30 to 200 μm in aluminum melt were investigated. The experimental results show that the particle-accumulated layer is formed in the periphery of the solidified specimen when the diameter of the separated molten metal, the magnetic induction intensity and the separation time are 10 mm, 0.04 T and 1 s, respectively. When the separation time is 2 s, the particle-accumulated layer can be observed obviously and the separation efficiency is about 80%. There are few alumina particles in the inner of the solidified specimen when the separation time is 3 s. The separation efficiency higher than 85% can be achieved when the separation time is longer than 3 s. When the magnetic induction intensity is 0.06 T, the visible particle-accumulated layer can be formed in 1 s and the separation efficiency is higher than 95%. The experimental results were compared with the calculated results at last.

Non-metallic particles, especially alumina, are the main inclusions in aluminum and its alloys. Numerical simulation and the corresponding experiments were carried out to study the motion behavior of alumina particles in commercial pure aluminum under high frequency magnetic field. At the meantime, multi-pipe experiment was also done to discuss the prospect of continuous elimination of non-metallic particles under high frequency magnetic field. It is shown that: 1) results of numerical simulation are in good agreement with the experimental results, which certificates the rationality of the simulation model; 2) when the intensity of high frequency magnetic field is 0.06 T, the 30 μm alumina particles in melt inner could migrate to the edge and be removed within 2 s; 3) multi-pipe elimination of alumina particles under high frequency magnetic field is also effective and has a good prospect in industrial application.

The electromagnetic, thermal and fluid fields during ISM (Induction Skull Melting)of TiAl alloy are simulated. The effects of ampere-turn, frequency and relative position between crucible and coil on the distribution of thermal and flow fields are numerically studied. The simulation model is verified by experiments and the simulation results are discussed in detail.

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 microstructure of sub-rapid solidification processed AZ61A magnesium alloy was presented and discussed. The results show that the grain size of the foil is significantly refined, and the grain morphology is cellular or globular. The eutectic transformation L → α -Mg+ β -Mg 17 Al 12 and microsegregation in conventionally solidified AZ61A alloy are suppressed to a great extent. The β -Mg 17 Al 12 phases located in the α -Mg grain boundaries are largely decreased due to high solidification cooling rate. As a consequence, the alloying elements Al, Zn, Mn show much higher solid solubility and the sub-rapid solidification microstructure dominantly consists of supersaturated α -Mg solid solution. The mechanical properties and fractographic analysis reveal that the fracture mechanism and corresponding morphology of the rapture surface of tensile bars are linked to the microstructure obtained and depend on the sub-solidification processes.

The results of experiments and simulations show that there is a turbulent flow in the molten aluminum and it is hard to be restrained in the thin tubule (diameter of 6 mm) when the electromagnetic body force is applied. The electromagnetic elimination experimental results show that the flow has serious effect on the elimination of 5 μm alumina inclusions, but has little effect on the 30 μm and 100 μm primary silicon. The effects of the electromagnetic field and the turbulent flow on the electromagnetic elimination are discussed.

In order to find the ways to improve the elimination efficiency with high frequency magnetic field, a mathematical model of electromagnetic elimination (EME) in the tubule with high frequency magnetic field was set up. The calculated results show that by ignoring the flow of molten metal, when the surface magnetic induction intensity of the metal ( B 0 ) is 0.03 T and the diameter of the tubule is 8 mm, the non-metallic inclusions with 30 μm diameter can be wiped off in 7 s from the center of the molten aluminum, whereas the elimination time of the 5 μm non-metallic inclusions is more than 240 s. When B 0 is 0.03 T, the diameter of the tubule is 8 mm and elimination time is more than 30 s, the elimination efficiency of 5μm, 10 μm and 30 μm non-metallic inclusions is about 60%, 90% and 100%, respectively, the elimination efficiency increases with the decreasing diameter of the tubule. It can be concluded that increasing the magnetic induction intensity or decreasing the diameter of the tubule can decrease the elimination time and improve the elimination efficiency in EME with high frequency magnetic field.

With admixture of n-diamond and diamond-like carbon powders (DLC) as carbon source, transparent wafers have been synthesized by hydrothermal process at 100 °C and atmosphere pressure. Scanning electron microscopy, X-ray diffraction, Raman spectroscopy, transmission electron microscopy, electron-probe microanalysis andFourier-transform infrared spectrometer were used to analyze those transparent wafers. These results indicated that the transparent wafers were amorphous sp3-banding carbon wafer, and that the wafers were not aggregate of DLC from the carbon source but a new kind of reaction product by hydrothermal treatment.

The fluctuation of the melt temperature in a tundish was measured during casting and experiments were conducted to investigate the effects of ultrasonic melt treatment on the surface quality and solidification structures of Al–1%Si ingots. The results show that the uniformity of melt temperature was enhanced with the application of ultrasonic melt treatment. When the ultrasonic power is 1000 W, the surface quality was evidently improved and grains of cast ingots were refined. Moreover, EPMA analysis was adopted to study the relationship between the ultrasonic power and boundary segregation of Si element. The result shows that boundary segregation is suppressed with the increase of ultrasonic power and the phenomenon was theoretically interpreted.

Cladding metals have been widely applied to many fields because they have many excellent physical, chemical and mechanical properties that can not be obtained from the single metals. There are many conventional processes for manufacturing cladding metals, for example roll bonding, diffusion bonding, explosive welding, extrusion cladding and casting cladding. Among these processes, continuous casting is an ideal process to prepare cladding metals which has the advantages of high production efficiency, low production cost and good interface bonding. This process can make two metals contact directly by the ways of one liquid-one liquid, one liquid-one solid or one liquid-one semi- solid and then the good metallurgical bonding can be obtained. So, this process is extensively studied by researchers engaging in material processing. The process of the direct water-cooled continuous casting to fabricate cladding 3003/4004 aluminum alloy circular ingot is researched in this paper. The 3003 aluminum alloy has excellent corrosion resistance, low strength and high melting point, while the 4004 aluminum alloy has poor corrosion resistance, high strength and low melting point. The cladding 3003/4004 aluminum alloy material can combine the advantages of two metals and can be widely used in many fields, especially in car engine and air conditioning heat sink. To obtain the good interface bonding, a special inner mold with the single-side cooling capability was applied in this process. By the special inner mold, the two alloys can make the contact of one liquid-one solid or one liquid-one

Solar cells are currently fabricated from a variety of silicon-based materials. Now the major silicon material for solar cells is the scrap of electronic grade silicon (EG-Si). But in the current market it is difficult to secure a steady supply of this material. Therefore, alternative production processes are needed to increase the feedstock. In this paper, EBM is used to purify silicon. MG-Si particles after leaching with an initial purity of 99.88% in mass as starting materials were used. The final purity of the silicon disk obtained after EBM was above 99.995% in mass. This result demonstrates that EBM can effectively remove impurities from silicon. This paper mainly studies the impurity distribution in the silicon disk after EBM.

In the experiment, acid leaching under an ultrasonic field (20 kHz, 80 W) was used to remove Al, Fe, and Ti impurities in metallurgical grade silicon (MG-Si). The effects of the acid leaching process parameters, including the particle size of silicon, the acid type (HCl, HNO3, HF,) and the leaching time on the purification of MG-Si were investigated. The results show that HCl leaching, an initial size of 0.1 mm for the silicon particles, and 8 h of leaching time are the optimum parameters to purify MG-Si. The acid leaching process under an ultrasonic field is more effective than the acid leaching under magnetic stirring, the mechanism of which is preliminarily discussed.