MICROSTRUCTURE AND MECHANICAL PROPERTY DEVELOPMENT IN THE SIMULATED HEAT AFFECTED ZONE OF V TREATED HSLA STEELS

The simulated heat affected zone （HAZ） of the high strength low alloy （HSLA） steels containing 0%, 0.047%, 0.097% and 0.151% vanadium, respectively, were studied with Gleeble-2000 thermomechanical simulator to determine the influence of vanadium addition on the mechanical properties of the HAZ. The HAZ simulation involved reheating the samples to 1350℃, and then cooling to ambient temperature at a cooling rate of 5℃/s ranging from 800 to 500℃ （△8/5=60s）. The mechanical properties including tensile strength and -20℃ impact toughness were conducted. The microstructures of the base steel and the simulated HAZs were investigated using optical microscope, scanning electron microscope （ SEM ） and transmission electron microscope （TEM）. Based on the systemutic examination, the present work confirmed that about 0.05% vanadium addition to low carbon low alloy steels resulted in expected balance of strength and toughness of the HAZ. And more than 0.10% levels addition led to detrimental toughness of the HAZ SEM study showed that the simulated 0.097% and 0.151%V HAZs consisted of more coarse ferrite plates with greater and more M-A constituents along austenite grain and ferrite plate bound- aries. The impact fracture surfaces of the simulated 0.097% and 0.151%V HAZs showed typically brittle mode with predominant cleavages. The size of the facet in the fracture surface increased with increasing vanadium level from 0.097% to 0.151%.As a result, the simulated 0.151% V HAZ has the lowest impact toughness of the four specimens.

Therapeutic Actions of the Chinese Herbal Formulae with Cold and Heat Properties and Their Effects on Ultrastructures of Synoviocytes in Rats of the Collagen-Induced Arthritis

The therapeutic actions of Qing Luo Yin (QLY清络饮) with heat property and Wen Luo Yin (WLY温络饮) with cold property on pain, swelling of the ankle, arthritis index and ultrastructures of synoviocytes were compared in rats of type II collagen-induced arthritis (CIA), with tripterygium glycosidorum (TG) used as control. The results indicated that both QLY and WLY could reduce pain, swelling of the ankle and the arthritis index of CIA, and QLY had better effects in reducing the swelling of the ankle and controlling the secondary pathological lesions as compared with WLY. Investigation on the ultrastructures of synoviocytes indicated that both QLY and WLY could reduce the number of Golgi apparatus, rough surface endoplasmic reticulum, dense bodies, matrix filaments and vacuoles so as to suppress the excessive secretion of synoviocytes in rats of CIA.

Formation Mechanism and Existing Form of Sb in Heat Resistance Mg-Gd-Y-Sb Alloy

The existing form and reaction mechanism of Sb in heat resistane Mg-Gd-Y-Sb rare earth magnesium alloy were investigated by inductive coupled plasma emission spectroscopy(ICP),scanning electron microscopy(SEM),energy dispersive spectroscopy(EDS),and X-ray diffraction(XRD).It is found that Sb tends to form high melting point intermetallics with rare earth elements of Gd and Y.The existing form of Sb is determined to be GdSb and SbY,respectively,which has high melting point(GdSb:2142℃/SbY:1782℃).Meanwhile,the first principle calculation and electronegativity difference calculation were performed to further understand the reaction mechanism.Therefore,the forming heat and binding energy were calculated.The experimental results show that the binding tendency of Sb element to Gd and Y is much stronger than that of it with other elements in this alloy,which results in the formation of high melting point of Gd-Sb and Y-Sb intermetallics,and finally leads to the high temperature resistant further improvement of the Mg-Gd-Y magnesium alloy.

Effect of Heat Treatment on Microstructure and Mechanical Properties of Si Cp/2024 Aluminum Matrix Composite

SiCp/2024 aluminum alloy matrix composite was prepared by powder metallurgy method. Effects of heat treatment on the microstructure and mechanical properties of composite were investigated by SEM, EDS, XRD, HREM, tensile and hardness tests. The experimental results showed that SiC particles distributed uniformly in the matrix and were in good combination with matrix. The tensile strength and hardness were improved significantly after heat treatment. With the increase of solid solution temperature, the alloy phases dissolved in the matrix gradually. When the solid solution temperature arrived at 505 ℃, the alloy phases dissolved thoroughly, and the composite exhibited the highest tensile strength and hardness（σb=360 MPa, HBS=104）. The main strengthening phase was Al2Cu, which was granular and distributed dispersively in the matrix. Effect of T6 was better than that of T4 at the same solid solution temperature.

Effect of Post-weld Heat Treatment on Mechanical Characteristics of AZ31 Magnesium Alloy Welded Joints

Tungsten inert gas（TIG） welding was performed on 2.7 mm thick commercial extruded AZ31 B magnesium alloy plates. We investigated the effect of post-weld heat treatment（PWHT） on the microstructure, mechanical properties and precipitated phase of the weld joints. The results showed that during the annealing treatment（200 ℃-1 h, 250 ℃-1 h, 300 ℃-1 h, 350 ℃-1 h, 400 ℃-1 h, and 450 ℃-1 h）, the average grain size in the weld seam was the minimum after annealing at 400 ℃ for 1 hour, and then abnormally grew up after annealing at 450 ℃ for 1 hour. The mechanical properties enhanced when the joints were processed from 200 ℃-1 h to 400 ℃-1 h but sharply decreased with increasing annealing temperature. In contrast to the annealing treatment, solution treatment（250 ℃-10 h, 300 ℃-10 h, 350 ℃-10 h, 400 ℃-10 h, and 450 ℃-10 h） exhibited a better ductility but a slight deterioration in tensile strength. Especially speaking, no eutectic compounds（such as Mg17 Al12） were observed in the weld seam. The supersaturated Al atoms were precipitated in a coarse spherical shape dispersed in the weld seam. The precipitated Al atoms dissolved in the matrix substances at the condition（400 ℃-1 h） or（250 ℃-10 h）. The solution treatment caused grain coarsening and precipitated Al atoms dissolved in the weld seam substantially, which resulted in a drop in micro-hardness at the weld seam compared to the area of the annealed joints.

Effect of aging temperature on the microstructures and mechanical properties of ZG12Cr9Mo1Co1NiVNbNB ferritic heat-resistant steel

The effect of aging on the mechanical properties and microstructures of a new ZG12Cr9 MolColNiVNbNB ferritic heat resistant steel was investigated in this work to satisfy the high steam parameters of the ultra-supercritical power plant.The results show that the main precipitates during aging are Fe（Cr,Mo）23C6,V（Nb）C,and（Fe2Mo） Laves in the steel.The amounts of the precipitated phases increase during aging,and correspondingly,the morphologies of phases are similar to be round.Fe（Cr,Mo）23C6 appears along boundaries and grows with increasing temperature.In addition,it is revealed that the martensitic laths are coarsened and eventually happen to be polygonization.The hardness and strength decrease gradually,whereas the plasticity of the steel increases.What＇s more,the hardness of this steel after creep is similar to that of other 9%-12%Cr ferritic steels.Thus,ZG12Cr9 MolColNiVNbNB can be used in the project.

Heat Transfer and Acoustic Properties of Open Cell Aluminum Foams

The aluminum open cell foams have been prepared by the conventional precision casting method to investigate the thermal and acoustic properties.A water heating system and silencers were organized as a first step for its applications.The temperature increase between the top and bottom of the foam became larger as the cell size increased in the heat transfer measurement.Sound absorption ratio of the close cell foams was 60%-100%, whereas the open cell aluminum foam showed only 10%-20% of sound absorption at low frequency.When the prototype electric water heater manufactured by combining aluminum open cell foam with a heater was heated to 100-400℃,the highest temperature of water was in the range of 16-46~C.This suggests that there could be potential for this type of heater to be used as a commercial electric water heater.Sound silencer made with the aluminum open cell foam was applied to exit of exhaustion side at air pressure line.Sound silencing effect of open-celled aluminum foam showed that the noise level went down by introducing smaller cell size foam.

Thermal Characterization of Lauric Acid and Stearic Acid Binary Eutectic Mixture in Latent Heat Thermal Storage Systems with Tube and Fins

In order to obtain the suitable phase change material（PCM） with low phase change temperature and improve its heat transfer rate, experimental investigation was conducted. Firstly, different mass ratios of lauric acid（LA） and stearic acid（SA） eutectic mixtures were prepared and characterized by differential scanning calorimetry（DSC）. Then, the performance of eutectic mixture during charging process under different fin widths in vertical condition, and performance during charging and discharging processes under different inlet temperature heat transfer fluid（HTF） in horizontal condition were investigated, respectively. The results revealed that the LA-SA eutectic mixture had the suitable phase change temperature and desired latent heat for low-temperature water floor heating system. Wide fins and high inlet temperature HTF significantly enhanced the transfer rate and decreased the melting time.

Microstructure and stress-rupture property of an experimental single crystal Ni-base superalloy with different heat treatments

The influence of heat treatment on the microstructure and stress-rupture property at 1,100 °C/140 MPa was investigated in a 5.0 wt% Re containing experimental single crystal Ni-base superalloy. The results indicate that the γmorphology is nearly cuboidal in the dendrite core after conventional heat treatment. The lattice misfit of alloy becomes more negative after modified heat treatment and results in more cuboidal γ precipitates than that after conventional heat treatment. The increased stress-rupture life after modified heat treatment is attributed to higher γ volume fraction, more negative lattice misfit, well-rafted structure, and narrower c channel width.

Theoretical Studies on the Structure and Detonation Properties of a Furazanbased Energetic Macrocycle Compound

Based on the full optimized molecular geometric structure at 6-311＋＋G＊＊ level,the density（ρ）,detonation velocity（D）,and detonation pressure（P） for a new furazan-based energetic macrocycle compound,hexakis[1,2,5]oxadi-azole[3,4-c：3＇,4＇-e;3＇＇,4＇＇-g：3＇＇＇,4＇＇＇-k：3＇＇＇＇,4＇＇＇＇-m：3＇＇＇＇＇,4＇＇＇＇＇-o][1,2,9,10]-tetraazacyclohexadecine,were investigated to verify its capacity as high energy density material（HEDM）. The infrared spectrum was also predicted. The heat of formation（HOF） was calculated using designed isodesmic reaction. The calculation on the bond dissociation energies（BDEs） was done and the pyrolysis mechanism of the compound was studied. The result shows that the N3–O1 bond in the ring may be the weakest one and the ring cleavage is possible to happen in thermal decomposition. The condensed phase HOF and the crystal density were also calculated for the title compound. The detonation data show that it can be considered as a potential HEDM. These results would provide basic information for the molecular design of novel high energy materials.

Enhanced Heat Transfer of Carbon Nanotube Nanofluid Microchannels Applied on Cooling Gallium Arsenide Cell

Carbon nanotube nanofluids have wide application prospects due to their unique structure and excellent properties.In this study,the thermal conductivity properties of carbon nanotube nanofluids and SiO2/water nanofluids were compared and analyzed experimentally using different preparation methods.The physical properties of nanofluids were tested using a Malvern Zetasizer Nano Instrument and a Hot Disk Thermal Constant Analyzer.Combined with field synergy theory analysis of the heat transfer performance of nanofluids,results show that the thermal conductivity of carbon nanotube nanofluids is higher than that of SiO2/water nanofluids,and the thermal conductivity of nanofluid rises with the increase of mass fraction and temperature.Moreover,the synergistic performance of carbon nanotube nanofluids is also superior to that of SiO2/water nanofluids.When the mass fraction of the carbon nanotube nanofluids is 10%and the SiO2/water nanofluids is 8%,their field synergy numbers and heat transfer enhancement factors both reach maximum.From the perspective of the preparation method,the thermal conductivity of nanofluids dispersed by high shear microfluidizer is higher than that by ultrasonic dispersion.This result provides some reference for the selection and use of working substance in a microchannel cooling concentrated photovoltaic and thermal(CPV/T)system.

Effect of friction stir processed microstructure on tensile properties of an Al-Zn-Mg-Sc alloy upon subsequent aging heat treatment

An as-cast Al-Zn-Mg-Sc alloy was friction stir processed varying tool related parameters, yielding microstructures with different grain sizes （0.68, 1.8 and 5.5 μm）. Significant increases in room temperature ductility were obtained in these materials with reasonable enhancement in strength. It is demonstrated that the type of microstructure produced by friction stir processing （FSP） has a significant influence on the choice of post-FSP heat treatment design for achieving improved tensile properties. It is also found that the ultrafine grained FSP material could not achieve the desired high strength during the post-FSP heat treatment without grain coarsening, whereas the micro-grained FSP materials could reach such strength levels （〉560 MPa） under conventional age hardening heat treatment conditions.

Effects of Heat Treatment on Surface Recrystallization and Stress Rupture Properties of a Fourth-Generation Single-Crystal Superalloy after Grit Blasting

The specimens of a fourth-generation single-crystal superalloy were grit-blasted and heat-treated in vacuum at 1100, 1150, 1200, 1250 and 1300 °C for 4 h, respectively. Then, the microstructure and the stress rupture properties of the recrystallized alloy were investigated at 1150 °C/120 MPa. The results showed that a cellular recrystallization occurred in the surface layer after heating at 1100, 1150 and 1200 °C for 4 h. An equiaxed recrystallization formed as the specimen was heat-treated at 1300 °C for 4 h, while a mixed recrystallization occurred in the specimen heat-treated at 1250 °C for 4 h. The recrystallized depth clearly increased with a rise of the heat treatment temperature. The stress rupture life continuously decreased with a rise of the heat treatment temperature up to 1250 °C. Although the overall stress rupture life reduced to different degrees, the stress rupture life of specimen after heat treatment at 1300 °C was relatively high and intermediate between those of specimens treated at 1150 and 1200 °C. The fact that the stress rupture life reduced to different degrees after heat treatment can be attributed to the recrystallization of the surface layer and to the microstructure evolution of the interior of the specimen. The small γ’ phase precipitated again after heat treatment at 1300 °C for 4 h. So,the stress rupture life was relatively longer than that after heat treatment at 1200 or 1250 °C although the equiaxed recrystallization formed in the surface layer.

Effects of Cr Content on the Microstructure and Properties of 26Cr–3.5Mo–2Ni and 29Cr–3.5Mo–2Ni Super Ferritic Stainless Steels

By using scanning electron microscopy, energy-dispersive spectrometry, X-ray diffraction, strength and hardness measurements, the microstructure, precipitation, mechanical properties, and corrosion resis- tance have been investigated for two super ferritic stainless steels, 26Cr-3.SMo-2Ni and 29Cr-3.5Mo- 2Ni, with the aim to consider the effect of Cr content. The results showed that with the addition of Cr content, the recrystallization temperature was increased; the precipitation of Laves and Sigma （o） phases was promoted and the mechanical properties of super ferritic stainless steel were modified. Further- more, the pitting corrosion resistance and corrosion resistance to H2SO4 of the two super ferritic stainless steels were improved. In addition, suitable annealing processing is a key factor to maintain integrated performance by optimizing microstructure and removing detrimental precipitation phases.

Effects of substitution of Nd in a sand-cast Mg-2.5Nd-0.6Zn-0.5Zr alloy with x wt.% Sm(x=2.5, 4, and 6)

The microstructures and mechanical properties of a series of sand-cast Mg-Sm-Zn-Zr alloys under ascast, solution-treated and peak-aged states were thoroughly investigated. The OM, XRD, SEM and HRTEM were employed to characterize the microstructural evolution. The results indicate that substitution Nd in the conventional Mg-2.5 Nd-0.6 Zn-0.5 Zr alloy with different contents of Sm has comparative grain refinement effect and will fully change the dominant intermetallic phase. In addition, the substituted alloys perform clearly higher strength with comparative ductility at both as-cast and peakaged conditions and much greater aging hardening response than the referential alloy. It is obvious that the strength increments of this alloy are attributed to the changes of the eutectic intermetallic particles on grain boundaries.

Synthesis and characterization of NaA zeolite particle as intumescent fiame retardant in chloroprene rubber system

NaA zeolite with average particle size of 1 μm was successfully synthesized by microwave heating. Influences of pre-crystallization time, microwave power and microwave heating time on the synthesis of NaA zeolite were investigated. The as-synthesized sample was characterized by X-ray diffraction （XRD）, scanning electron microscopy （SEM） and particle size distribution （PSD）. Thermal and flame retardant properties as intumescent flame retardant （IFR） in chloroprene rubber （CR） system, such as thermogravimetry （TG）, limiting oxygen index （LOI）, burning rate （BR） and specific extinction area （SEA） were further investigated by adding NaA zeolite particles to CR. Experimental results show that the thermal stability and LO1 value increased while BR and SEA decreased by adding 5 phr NaA zeolite into the 40 phr IFR filled CR system.

On the nanoparticulate flow

Nanoparticulate flows occur in a wide range of natural and engineering applications hence have received much attention. The purpose of the present paper is to provide a brief review on the research on the nanoparticulate flow in some aspects which consist of the method of moment for solving the particle population balance equation, penetration efficiency, pressure drop and heat transfer in the turbulent nanoparticulate pipe flow, fluctuating-lattice Boltzrnann model for Brownian motion of nanoparticles.

Thermal conductivity of micro/nano-porous polymers: Prediction models and applications

Micro/nano-porous polymeric material is considered a unique industrial material due to its extremelylow thermal conductivity, low density, and high surface area. Therefore, it is necessary to establishan accurate thermal conductivity prediction model suiting their applicable conditions and provide atheoretical basis for expanding their applications. In this work, the development of the calculationmodel of equivalent thermal conductivity of micro/nano-porous polymeric materials in recent yearsis summarized. Firstly, it reviews the process of establishing the overall equivalent thermal conductivity calculation model for micro/nanoporous polymers. Then, the predicted calculation models ofthermal conductivity are introduced separately according to the conductive and radiative thermalconductivity models. In addition, the thermal conduction part is divided into the gaseous thermalconductivity model, solid thermal conductivity model and gas-solid coupling model. Finally, it isconcluded that, compared with other porous materials, there are few studies on heat transfer of micro/nanoporous polymers, especially on the particular heat transfer mechanisms such as scale effectsat the micro/nanoscale. In particular, the following aspects of porous polymers still need to be furtherstudied: micro scaled thermal radiation, heat transfer characteristics of particular morphologies at thenanoscales, heat transfer mechanism and impact factors of micro/nanoporous polymers. Such studieswould provide a more accurate prediction of thermal conductivity and a broader application in energyconversion and storage systems.

Synthesis of a novel naphthyl-based self-catalyzed phthalonitrile polymer

A novel naphthyl-based self-catalyzed phthalonitrile monomer was prepared via nucleophilic displacement reaction. The structure was characterized by Fourier infrared spectrum （FT-IR） and nuclear magnetic resonance （^1H NMR）. The polymerization mechanism was explored. Thermal properties were characterized by differential scanning calorimetry （DSC） and thermogravimetric analysis （TGA）, which demonstrated self-promoted behavior and excellent heat resistance.

Applications of low temperature calorimetry in material research

Low temperature calorimetry is an experimental method of heat capacity measurements, and heatcapacity is one of the most important and fundamental thermodynamic properties of substances. Theheat capacity can provide an average evaluation of the thermal property of a sample since it is a bull（property of substances. In the other hand, the condensed states of substances could be mainly controlledby the molecular motions, intermolecular interactions, and interplay among molecular structures. Thephysical property reflected in a material may be closely related to the energy changes in these threefactors, which can be directly observed in a heat capacity curve. Therefore, low temperature calorimetryhas been used not only to obtain heat capacity, entropy, enthalpy and Gibbs free energy, but also toinvestigate and understand lattice vibrations, metals, superconductivity, electronic and nuclearmagnetism, dilute magnetic systems and structural transitions. In this review, we have presented theconcept of low temperature calorimetry and its applications in the related field of material researches,such as nano-materials, magnetic materials, ferroelectric materials, phase change materials and othermaterials.