Spray Atomized and Codeposited Al-Li Based Metal-matrix Composites Processing and Properties

In spray atomization and codeposition, a molten stream of metal is disintegrated into a fine dispersion of droplets by high velocity gas jets. The resulting semi-solidified droplets are directed towards a substrate where they impact and collect as rapidly solidified splats. Relatively high rates of solidification are achieved as a result of the thinness of the splats and the rapid heat extraction during flight and upon impacting with the substrate. The processing method uses codeposition of the metallic semi-solidified droplets (metallic matrix) with the injected reinforcement ceramic particles. In the present paper, the microstructures, mechanical properties, interfacial properties, thermal stability and aging behaviour of spray atomized and codeposited Al-Li-X MMC's (injected X=SiC, Al2O3) are reported and correlated to the processing conditions.

Influence of core sand properties on flow dynamics of core shooting process based on experiment and multiphase simulation

The influence of core sand properties on flow dynamics was investigated synchronously with various core sands, transparent core-box and high-speed camera. To confirm whether the core shooting process has significant turbulence, the flow pattern of sand particles in the shooting head and core box was reproduced with colored core sands. By incorporating the kinetic theory of granular flow(KTGF), kinetic-frictional constitutive correlation and turbulence model, a two-fluid model(TFM) was established to study the flow dynamics of the core shooting process. Two-fluid model(TFM) simulations were then performed and a areasonable agreement was achieved between the simulation and experimental results. Based on the experimental and simulation results, the effects of turbulence, sand density, sand diameter and binder ratio were analyzed in terms of filling process, sand volume fraction(αs) and sand velocity(Vs).

Evolution of microstructure and mechanical properties of A356 aluminium alloy processed by hot spinning process

The evolution of microstructure and mechanical properties of A356 aluminum alloy subjected to hot spinning process has been investigated. The results indicated that the deformation process homogenized microstructure and improved mechanical properties of the A356 aluminum alloy. During the hot spinning process, eutectic Si particles and Fe-rich phases were fragmented, and porosities were eliminated. In addition, recrystallization of Al matrix and precipitation of Al Si Ti phases occurred. The mechanical property testing results indicated that there was a significant increase of ductility and a decrease of average microhardness in deformed alloy over die-cast alloy. This is attributed to uniform distribution of finer spherical eutectic Si particles, the elimination of casting defects and to the recrystallized finer grain structure.

Effect of Rolling Process on Comprehensive Properties of Corrosion Resistant Steel for Bottom Plate of Cargo Oil Tanks

A new kind of corrosion resistant steelfor cargo oiltanks（COT）was developed.The influences of finalrolling temperature,cooling rate,and finalcooling temperature on microstructure were investigated.The proper rolling process parameters were obtained through multi-pass thermalsimulation test.The finalrolling temperature is about 820 ℃,the finalcooling temperature is about 600 ℃,and the cooling rate should be controlled between 10 ℃/s and 20 ℃/s.Based on the above analysis of the results,three groups of rolling samples by thermo mechanicalcontrolprocess are prepared.The tensile strength,yield strength,and toughness of the corrosion resistant steelare measured,which meet the requirements of DH36 steel,it can instruct the actualrolling production.The corrosion behaviour is also researched by weight loss and electrochemicalimpedance spectroscopic method,and it is found that the steelhas good corrosion resistance performance,the best one is No.3 steel,the corrosion rate of which is about 1/4 of the accepted criterion.

Comparative Study on Processing Property Between CWW CO_2 Gas Shielded Welding and SAW

Cable welding wire（CWW）CO2gas shielded welding is an innovative process arc welding with high efficiency,high quality and low consumption,in which cable wire is used as consumable electrode.CWW CO2gas shielded welding and submerged arc welding（SAW）are used for contrast studies on processing property of high strength steel A36used in ship structure.The results show that the shapes of weld seam,using CWW CO2gas shielded welding and SAW,are good and no weld defect such as air hole,flaw,slag inclusion,incomplete fusion,lack of penetration and so on are found in the weld seam.Because the rotating of arc during CWW CO2gas shielded welding process has a strong stirring effect on molten pool,the grain in the heat affected zone（HAZ）of the joints,using CWW CO2 gas shielded welding,is small.Tensile failure positions of joints by CWW CO2gas shielded welding and SAW are all in the base metal,but tensile strength of CWW CO2gas shielded welding joint is higher than that of SAW joint by an average of 2.3%.The average impact energy of HAZ,using CWW CO2gas shielded welding and SAW,is almost equal,but the average impact energy of the weld seam using CWW CO2gas shielded welding is increased by 6%,and the average impact energy of the fusion line is increased by 7%.The 180°bending tests for the joints of CWW CO2 gas shielded welding and SAW are all qualified,and the joints hardness is all less than HV 355,but hardness of CWW CO2gas shielded welding wire welding joint near the fusion line is obviously lower.It can be concluded that the properties of CWW CO2gas shielded welding are better than those of the SAW joint,and CWW CO2gas shielded welding is suitable for welding high strength steel A36used in ship structure.

Prediction and experimental measurement of the electromagnetic thrust generated by a microwave thruster system

A microwave thruster system that can convert microwave power directly to thrust without a gas propellant is devel-oped. In the system, a cylindrical tapered resonance cavity and a magnetron microwave source are used respectively as the thruster cavity and the energy source to generate the electromagnetic wave. The wave is radiated into and then reflected from the cavity to form a pure standing wave with non-uniform electromagnetic pressure distribution. Consequently, a net electromagnetic thrust exerted on the axis of the thruster cavity appears, which is demonstrated through theoretical calcula- tion based on the electromagnetic theory. The net electromagnetic thrust is also experimentally measured in the range from 70 mN to 720 mN when the microwave output power is from 80 W to 2500 W.

Effect of M/P and Borax on the Hydration Properties of Magnesium Potassium Phosphate Cement Blended with Large Volume of Fly Ash

The effect of the borax content and magnesia to phosphate ratio（M/P） on the hydration properties of the magnesium potassium phosphate cement（MKPC） with large volume of fly ash was investigated, and a five-hydration-stage for MKPCs was proposed. The results show that MKPC sets rapidly with less than 8% of borax, which is unfavorable to the application of MKPC on construction. Adding more than 8%（including 8%） of borax results in a secondary hydration peak for MKPC, in which the process of hydration can be divided into five stages, namely, pre-induction period, induction period, acceleration period, deceleration period and stable period. M/P ratios could not change the multi-step reactive stages but higher M/P ratios could accelerate the hydration. Borax tends to impact the formation of Mg-containing hydrated products.

Cost-effective integrated strategy for the fabrication of hard-magnet barium hexaferrite powders from low-grade barite ore

Ultrafine barium hexaferrite（BaFe12O19） powders were synthesized from the metallurgical extracts of low-grade Egyptian barite ore via a co-precipitation route. Hydrometallurgical treatment of barite ore was systematically studied to achieve the maximum dissolution efficiency of Fe（～99.7%） under the optimum conditions. The hexaferrite precursors were obtained by the co-precipitation of BaS produced by the reduction of barite ore with carbon at 1273 K and then dissolved in diluted HCl and FeCl3 solution at pH 10 using NaOH as a base; the product was then annealed at 1273 K in an open atmosphere. The effect of Fe^3＋/Ba^2＋ molar ratio and the addition of hydrogen peroxide（H2O2） on the phase structure, crystallite size, morphology, and magnetic properties were investigated by X-ray diffraction, scanning electron microscopy, and vibrating sample magnetometry. Single-phase BaFe（12）O（19） powder was obtained at an Fe^3＋/Ba^2＋ molar ratio of 8.00. The formed powders exhibited a hexagonal platelet-like structure. Good maximum magnetization（48.3 A×m^2×kg^–1） was achieved in the material prepared at an Fe^3＋/Ba^2＋ molar ratio of 8.0 in the presence of 5% H2O2 as an oxidizer and at 1273 K because of the formation of a uniform, hexagonal-shaped structure.

Collaborative optimization design of process parameter and structural topology for laser additive manufacturing

High-resolution laser additive manufacturing(LAM)significantly releases design free-dom,promoting the development of topology optimization(TO)and advancing structural design methods.In order to fully take advantage of voxelated forming methods and establish the quantitative relationship between the mechanical properties of printing components and multiple process factors(laser-and process-parameters),the concurrent optimization design method based on LAM should cover the process-performance relationship.This study proposes a novel artificial intelligence-facilitated TO method for LAM to concurrently design microscale material property and macroscale structural topology of 3D components by adopting heuristic and gradient-based algorithms.The process–structure–property relationship of selective laser sintering is established by the back propagation neural network,and it is integrated into the TO algorithm for providing a systematic design scheme of structural topology and process parameter.Compared with the classical optimization method,numerical examples show that this method is able to improve the mechanical performance of the macrostructure significantly.In addition,the collaborative design method is able to be widely applied for complex functional part design and optimization,as well as case studies on artificial intelligence-facilitated product evaluation.

Effects of doping Fe and Al on microstructure and electrochemical characteristics of Mg-based hydrogen storage alloys

The Mg-based hydrogen storage alloys Mg2Ni, Mg2Ni0.7Fe0.3 and Mgl.7Alo.3Ni were successfully synthesized by a two-step process （sintering and ball milling）. The crystal structure and microstructure were examined by X-ray diffraction, Scanning Electron Microscope and Malvern particle size analyzer. New phase appears in the tripe alloys doped with A1 and Fe, and the particle size ranges from 3μm to 5 μm. The electrochemical performance studies indicate that the partial substitution of AI for Mg, and Fe for Ni significantly improve the cycle life, reversibility of hydrogen absorption and desorption. The diffusion process is the control step in the electrode reaction of hydrogen storage alloys.

Microstructure and Performance Analysis of Organic Coating under High Temperature and High CO_2 Partial Pressure

To evaluate the property of the organic coatings in oil and gas plants, the aging process was studied in high temperature and high CO_2 partial pressure environment. Correlations were developed between the macroscopic properties and microstructure of the organic coatings. The surface appearance, mechanical properties, and permeability of the organic coatings were measured. Furthermore, the crystal structure of the organic coatings was investigated through synchrotron radiation grazing incidence X-ray diffraction（GIXRD） on the BL14B1 beam line in Shanghai Synchrotron Radiation Facility. Combined with the Fourier transform infrared spectroscopy, the molecular structure of the organic coatings was investigated. The experimental results indicate that the thickness variation and weight loss of the organic coatings increase with the immersion time, and the penetration resistance of the coating obviously decreases as the temperature rises. Moreover, the degradation of the organic coatings with immersion time in high temperature and high CO_2 partial pressure environment is caused by the amorphization of the organic coatings as the groups and bonds of the organic coatings were not damaged.

Synthesis and Characterization of Cubic Zinc Titanate Doped with Lithium

Cubic （Zn,Li）TiO3 powders were synthesized through a modified sol-gel route including the Pechini process via a three-step heat treatment.The as-synthesized （Zn,Li）TiO3 could be stable up to 1000 °C.The dielectric constant and dielectric loss tangent of all the synthesized （Zn,Li）TiO3 samples at different measurement frequencies showed the similar tendency.At the same frequency,the dielectric constant and the dielectric loss tangent of （Zn,Li）TiO3 samples decreased and increased,respectively,with the lithium doping content increase.The as-prepared （Zn,Li）TiO3 showed improved microwave dielectric properties,and its maximum value of quality factor could reach 34000 GHz.

Electrical and dielectric characterization of Au/ZnO/n-Si device depending frequency and voltage

Au/Zn O/n-type Si device is obtained using atomic layer deposition（ALD） for Zn O layer, and some main electrical parameters are investigated, such as surface/interface state（Nss）, barrier height（Φb）, series resistance（Rs）, donor concentration（Nd）, and dielectric characterization depending on frequency or voltage. These parameters are acquired by use of impedance spectroscopy measurements at frequencies ranging from 10 k Hz to 1 MHz and the direct current（DC） bias voltages in a range from-2 V to ＋2 V at room temperature are used. The main electrical parameters and dielectric parameters,such as dielectric constant（ε＂）, dielectric loss（ε＂）, loss tangent（tan δ）, the real and imaginary parts of electric modulus（M and M）, and alternating current（AC） electrical conductivity（σ） are affected by changing voltage and frequency. The characterizations show that some main electrical parameters usually decrease with increasing frequency because charge carriers at surface states have not enough time to fallow an external AC signal at high frequencies, and all dielectric parameters strongly depend on the voltage and frequency especially in the depletion and accumulation regions. Consequently, it can be concluded that interfacial polarization and interface charges can easily follow AC signal at low frequencies.

Rare Earth Dragons

The invention covers the process for preparing an oxide complex that can absorb and release oxygen. The covered procedures include:preparation of CeO2, ZrO2 and HfO2 as raw material; preparation of the complex oxide with the raw material by employing heating and deoxidation method;and the process for re-heating and oxidizing the deoxidized complex oxide.

NbB_(2)Modified Al-Cu Alloys Fabricated by Freeze-Ablation Casting under High Cooling Rate Solidification

At present,improving the properties of aluminum alloys is generally achieved by increasing the cooling rate of the melt and adding micro-nano particles.Controlling the cooling rate of the melt to improve the refining effect of grain refiner is still a difficult problem in the aluminum alloy casting industry.An innovative and environmentally friendly casting process,known as freeze ablation,was introduced during the preparation of an Al–NbB_(2) intermediate alloy.This process significantly enhanced the cooling rate of the melt.The results indicated that the Al–NbB_(2) intermediate alloy produced under high cooling rates had a noticeable refining effect on Al–Cu alloys,with smaller NbB2 particles demonstrating superior refining performance.The average grain size of the refined Al–Cu alloy decreased from 154 to 69μm,the tensile strength increased by 12%,the fluidity increased by 18.4%,and the hot tearing index decreased from 144 to 12.The matching degree between NbB_(2) andα-Al was calculated using high-resolution transmission electron microscopy and the edge-to-edge model.It was found that the atomic interplanar spacing and the interatomic spacing mismatch between NbB_(2)’s<1120>plane and Al were both less than 10%,which further proved that NbB2 could serve as an effective nucleation site forα-Al grains to achieve grain refinement.

Photocatalytic properties of hierarchical BiOXs obtained via an ethanol-assisted solvothermal process

In this study, bismuth oxyhalide（Bi OXs（X_Cl, Br, I）） semiconductors were prepared by a simple solvothermal method, with ethanol serving as solvent and a series of tetrabutylammonium halide surfactants as halogen sources. Under identical synthetic conditions, Bi OBr was more readily constructed into regular flower-like hierarchical architectures. The photocatalytic properties of the materials were studied by monitoring the degradation of rhodamine B（Rh B）,with visible light absorption, and colorless salicylic acid（SA）. It was found that both Rh B and SA were rapidly degraded on the surface of Bi OBr. Bi OCl was rather active for the degradation of Rh B,but ineffective toward the degradation of SA. However, neither Rh B nor SA could be degraded effectively in the case of Bi OI. Further experiments such as UV–visible spectroscopy and detection of U OH and O2 Uradicals suggest that the electronic structure of the Bi OX photocatalysts is responsible for the difference in their activities.

Optimal design of hot rolling process for C-Mn steel by combining industrial data-driven model and multi-objective optimization algorithm

A successful mechanical property data-driven prediction model is the core of the optimal design of hot rolling process for hot-rolled strips. However, the original industrial data, usually unbalanced, are inevitably mixed with fluctuant and abnormal values. Models established on the basis of the data without data processing can cause misleading results, which cannot be used for the optimal design of hot rolling process. Thus, a method of industrial data processing of C-Mn steel was proposed based on the data analysis. The Bayesian neural network was employed to establish the reliable mechanical property prediction models for the optimal design of hot rolling process. By using the multi-objective optimization algorithm and considering the individual requirements of costumers and the constraints of the equipment, the optimal design of hot rolling process was successfully applied to the rolling process design for Q345B steel with 0.017% Nb and 0.046% Ti content removed. The optimal process design results were in good agreement with the industrial trials results, which verify the effectiveness of the optimal design of hot rolling process.

Friction-stir welding and processing of Ti-6Al-4V titanium alloy:A review

In this work, the current understanding and development of fliction-stir welding and processing of Ti- 6Al-4V alloy are briefly reviewed. The critical issues of these processes are addressed, including welding tool materials and design, tool wea,, processing temperature, material flow, processing window and residual stresses. A particular emphasis is given to microstructural aspects and microstructure-properties relationship. Potential engineering applications are highlighted.

Effect of Different Aging Processes on the Microstructure and Mechanical Properties of a Novel Al–Cu–Li Alloy

The effects of different aging processes on the microstructure and mechanical properties of a novel Al-Cu-Li alloy have been investigated by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. It is found that the tensile properties of a novel Al-Cu-Li alloy are sensitive to aging processes, which correspond to different microstructures. σ（Al_5Cu_6Mg_2） and T_1（Al_2CuLi） phases are the major precipitates for the alloy in T6 aging condition（165 ℃/60 h）. After duplex aging condition（150 ℃/24 h ＋ 180 ℃/12 h）, σ, θ＇（Al_2Cu） and T_1 phases are detected. Only the T_1 phases can be found in the T8 state alloy（6% pre-strain＋135 ℃/60 h）. The failure modes of alloy in T6 and duplex aging conditions are dimple-intergranular fracture, while typical quasi-cleavage fracture in T8 condition.

Semisolid-rolling and annealing process of woven carbon fibers reinforced Al-matrix composites

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.