Role of Heat Treatment Temperatures on Mechanical Properties and Corrosion Resistance Properties of Mg-10.16Li-8.14Al-1.46Er alloy

The microstructure and phase evolution of Mg-10.16Li-8.14Al-1.46Er alloy of as-cast,250℃+12 h,300℃+12 h,and 400℃+12 h were studied by optical microscopy,scanning electron microscope,and X-ray diffraction.The mechanical properties of Mg-10.16Li-8.14Al-1.46Er alloy in different states were tested by microhardness tester and tension tester.The corrosion resistance of Mg-10.16Li-8.14Al-1.46Er alloy in different states was measured by electrochemical workstation combined with hydrogen evolution and mass loss tests.The results show that the microstructure of as-cast Mg-10.16Li-8.14Al-1.46Er alloy consists ofα,β,AlLi,Al3Er and MgAlLi_(2)phases.Changes of microstructure are morphology and quantity ofαphase,and second phases of MgAlLi_(2)and AlLi by heat treatments at different temperatures.The best comprehensive tensile properties of Mg-10.16Li-8.14Al-1.46Er at 400℃are attributed to theαphase structure,solution strengthening and second phase strengthening.After heat treatments at different temperatures,the corrosion resistance of Mg-10.16Li-8.14Al-1.46Er was improved compared with as-cast samples.The Mg-10.16Li-8.14Al-1.46Er alloy has the best corrosion resistance at 250℃due to the best homogenization at this temperature.

Review on corrosion resistance properties of Inconel 718 alloy used in the oil and gas industry

This paper summarizes the corrosion behavior of Inconel 718 alloy, which is used in the oil and gas fields, including its uniform corrosion, pitting, intergranular corrosion, galvanic corrosion, stress corrosion, and hydrogen embrittlement. It also analyzes the main reasons for the good corrosion resistance of Inconel 718 alloy. This paper focuses on the effects of the heat-treatment process on corrosive behavior and provides guidelines for reasonable heat treatments in security service environments. Finally, this paper recommends further studies and applications of Inconel 718 in corrosion environments with high-temperature,high-pressure, and wet H2 S.

IMPROVEMENT ON TENSILE PROPERTIES AND CREEP RESISTANCE OF Fe 3Al BASED ALLOYS

Effects of alloying processing on tensile test properties of Fe 3Al based alloys have been studied. Results show that microalloying of cerium is very effective on increasing the room temperature ductility of Fe 3Al based alloys. Surface analysis by XPS demonstrates that cerium addition causes the change in the oxide chemistry and provides rapid passivation of the specimen surface. The high temperature strength and creep resistance of Fe 3Al based alloys can be significantly enhanced by alloying additions of tungsten, niobium or molybdenum, especially when combined additions of tungsten with niobium or molybdenum are used. The additions of tungsten, niobium or molybdenum also result in the significant microstructural refinement and the formation of fine precipitates which are identified as M 6C type carbide in the alloys containing tungsten.

Tungsten-containing high-entropy alloys: a focused review of manufacturing routes, phase selection, mechanical properties, and irradiation resistance properties

Alloying is one of the most effective means to confer superior properties to metal materials.For far too long,conventional W-based alloys were generally improved by the addition of minor elements.The exploitation of conventional W-based alloy is restricted to the corner of multielement phase diagrams with tiny compositional space.High-entropy alloys(HEAs)are a novel kind of alloys consisting of multi-principal alloying elements(usually more than 4)and have attracted increasing attention,since they were first reported in 2004.The emergence of HEAs filled the gap of the unexplored central region of multielement phase diagrams.Among them,tungsten-containing HEAs(TCHEAs)exhibit excellent mechanical properties,especially at extraordinarily elevated temperatures.Moreover,recent studies showed that TCHEAs had outstanding irradiation resistance properties.TCHEAs might serve as a promising candidate for plasma-facing materials in the fusion reactor.Many characteristics of TCHEAs are different from other HEAs due to the addition of tungsten with ultrahigh-melting temperature.Here,this paper aimed to introduce the manufacturing routes of TCHEAs;review the phase selection,mechanical properties,and irradiation resistance properties of TCHEAs;and propose the future prospects of TCHEAs.

Synthesis and Characterization of Fluorinated Polyurethane Containing Carborane in the Main Chain: Thermal, Mechanical and Chemical Resistance Properties

In this study, two fluorinated polyurethanes（FPU） containing carborane groups in the main chains were firstly designed and synthesized via the reaction of hexamethylene diisocyanate trimer（HDI trimer） with fluorinated polyesters（CFPETs） having hydroxyl-terminated carborane groups at room temperature. The structures of carborane fluorinated polyesters（CFPETs） and polyurethanes（CFPUs） were characterized by gel permeation chromatography（GPC）, Fourier transform infrared（FTIR） spectroscopy and nuclear magnetic resonance（NMR） measurements. The thermal stability, mechanical properties, Shore A hardness, solvent resistance and acid-alkali resistance of the carborane fluorinated polyurethane films were also studied. Thermogravimetric analysis（TGA） tests manifested that the introduction of carborane groups into the main chain of fluorinated polyurethane endowed the obtained fluorinated polyurethane with excellent thermal stability. The thermal decomposition temperature of carborane fluorinated polyurethane（CFPU） increased by 190 °C compared with that of the carborane-free fluorinated polyurethane（FPU）. Even at 800 °C, CFPU showed the char yield of 66.5%, which was higher than that of FPU（34.3%）. The carborane-containing fluorinated polyurethanes also showed excellent chemical resistance and prominent mechanical property even after the cured films being immersed into Jet aircraft oil or 37% HCl for 168 h or at high temperature（700 °C）. It is found that the structural characteristics of carborane group and the compacted structure of CFPU effectively improve the thermal stability, mechanical property, solvent resistance and acid-alkali resistance of the carborane-free fluorinated polyurethane. These excellent properties make CFPU as the useful raw materials to prepare the high temperature resistant coatings or adhesives for automotive engines, engine or fuel tank of aircraft and other equipment working in high-temperature or high concentrations of acid-alkali environments.

Resistance Switching Properties of Ag/Zn Mn_2O_4/p-Si Fabricated by Magnetron Sputtering for Resistance Random Access Memory

A resistance random access memory（RRAM） with a structure of Ag/ZnMn2O4/p-Si was fabricated by magnetron sputtering method. Reliable and repeated switching of the resistance of ZnMn2O4 fi lms was obtained between two well-defi ned states of high and low resistance with a narrow dispersion and 3V switching voltages. Resistance ratio of the high resistance state and low resistance state was found in the range of around 10^3 orders of magnitude and up to about 10^3 test cycles. The retention time of Ag/ZnMn2O4/p-Si device is longer than 10^6 seconds and the resistance ratio between two states remains higher than 10^3 at room temperature, showing a remarkable reliability performance of the RRAM devices for nonvolatile memory application. The equivalent simulation circuits for HRS（high resistance state） and LRS（low resistance state） were also studied by impedance spectroscopy.

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.

Influence of chemical composition on corrosion resistance of AZ91D magnesium alloy ingots

The influence of chemical composition on corrosion resistance of AZ91D magnesium alloys ingots has been investigated. Mass loss method was applied to evaluate the corrosion resistance of AZ91D alloys and the data were analyzed by multiple regression. The results show that the corrosion resistance of this alloy can be improved by increasing Al, Zn and Mn in a certain degree, and will drop with increasing Si and heavy metals (Fe, Cu, Ni). It is found that ingots received from company F should be listed into unusable materials in terms of the corrosion resistance, while among the five suppliers, the only local company E supplied excellent AZ91D magnesium alloy ingots with the best corrosion resistance.

Effects of ECAE processing temperature on the microstructure, mechanical properties, and corrosion behavior of pure Mg

A two-step equal channel angular extrusion（ECAE） procedure was used to process pure Mg. The effects of ECAE processing temperature on the microstructure, mechanical properties, and corrosion behavior of pure Mg were studied. The results show that the average grain size of pure Mg decreases with decreasing extrusion temperature. After ECAE processing at 473 K, fine and equiaxed grains（~9 μm） are obtained. The sample processed at 473 K exhibits the excellent mechanical properties, whereas the sample processed at 633 K has the lowest corrosion rate. The improved corrosion resistance and mechanical properties of pure Mg by ECAE are ascribed to grain refinement and microstructural modification.

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.

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.

Resistivity and Radio-Frequency Properties of Two-Generation Trap-Rich Silicon-on-Insulator Substrates

Crystal morphologies and resistivity of polysilicon trap-rich layers of two-generation trap-rich silicon-on-insulator（TR-SOI） substrates are studied. It is found that the resistivity of the trap-rich layer of generation 2（TR-G2）is higher than that of generation 1（TR-G1）, although the crystal morphologies of the trap rich layers are the same. In addition, the rf performance of two-generation TR-SOI substrates is investigated by coplanar waveguide lines and inductors. The results show that both the rf loss and the second harmonic distortion of TR-G2 are smaller than those of TR-G1. These results can be attributed to the higher resistivity values of both the trap-rich layer and the high-resistivity silicon（HR-Si） substrate of TR-G2. Moreover, the rf performance of the TR-SOI substrate with thicker buried oxide is slightly better. The second harmonics of various TR-SOI substrates are simulated and evaluated with the harmonic quality factor model as well. It can be predicted that the TR-SOI substrate will see further improvement in rf performance if the resistivities of both the trap-rich layer and HR-Si substrate increase.

Effect of Si_3N_4 on Resistance of Magnesia Based Castable

The magnesia based curable specimens with different Si3N4 contents were casted using sintered magnesite （w（MgO）=95%） as starting material, SiO2 micro-powder as binder, 0.3%, 4% and 5% β-Si3N4 powder replacing the equal addition of magnesia powder respectively. The slag resistance test was carried out at 1550℃ for 3h using Baosteel tundish slag and static crucible method. The result indicates that： introducing Si3N4 could obviously improve the slag resistance of MgO based castable, which increased with increasing Si3N4. Dense SiO2 sintered layer formed on the surface of magnesia based castable because of the oxidation of Si3N4 addition, which can prevent the further slag penetration. In the deep inner of castable, the partial-pressure of oxygen was very low, so Si3N4 can exist stably. Meanwhile in reducing atmosphere, Si3N4 was hard to be sintered, which resulted in the loose interior structure of MgO based castable.

A novel route to enhance high-temperature mechanical property and thermal shock resistance of low-carbon Mgo-C bricks by introducing ZrSiO_(4)

Conventional MgO-C bricks(graphite content>14 wt.%)produce a great deal of greenhouse gas emission,while low-carbon MgO-C bricks have serious thermal shock resistance during high-temperature service.To enhance the high-temperature mechanical property and thermal shock resistance of low-carbon MgO-C bricks,a novel route of introducing ZrSiO_(4) powder into low-carbon MgO-C bricks was reported in such refractories with 2 wt.% flaky graphite.The results indicate that the low-carbon MgO-C brick with 0.5 wt.%ZrSiO_(4) addition has the maximum hot modulus of rupture at 1400℃ and the corresponding specimen fired in the carbon embedded atmosphere has the maximum residual strength ratio(98.6%)after three thermal shock cycles.It is found that some needle-like AlON and plate-like Al_(2)O_(3)-ZrO_(2) composites were in situ formed in the matrices after the low-carbon MgO-C bricks were coked at 1400℃,which can enhance the high-temperature mechanical property and thermal shock resistance due to the effect of fiber toughening and particle toughening.Moreover,CO_(2) emission of the newly developed low-carbon MgO-C bricks is reduced by 58.3% per ton steel after using them as the working lining of a 90 t vacuum oxygen decarburization ladle.

Study on Marine Corrosion and Antifouling Behavior of Copper Alloys Exposed to Sea Areas in China

The relationship of corrosion resistance and antifouling behavior of 19 Cu alloys exposed to seawater of Qingdao ,Xiamen,Yulin sea areas in China for 1,2,4,8 year intervals was studied .The experiments were carried on by analyzing the composition of corrosion films formed on the surface of alloy specimens during the immersion time and by using OM,SEM,EDXA and AES experiment methods.The results verify the view point that it is the cuprous oxide film which played an important role in antifouling property of Cu alloys in seawater and throw a light on the view point in details further.The influence of different sea areas on the antifouling property of Cu alloys is also discussed.

Microstructure and wear behavior of laser cladding Ni-based alloy composite coating reinforced by Ti(C,N) particulates

In this paper, Ni-based alloy composite coating reinforced by Ti （C, N） particles was fabricated on the mild steel through laser cladding technology. The microstrncture of laser cladding layer was analyzed by means of optical microscopy （OM）, X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The wear resistance test of the coating was evaluated using an M-2000 tester. The results showed that the Ni-based composite coating had an ability of rapid solidification to form dendritic crystals microstructure consisting of Ti （ C, N） particulates uniformly distributed in the matrix. It was found that some Ti（ C,N） particles are similar to be round in shape, and the others are irregular. Laser cladding layer reinforced by Ti（ C, N） particulates was found to possess good wear resistance property.

Comparative Study on Optical Properties and Scratch Resistance of Nanocomposite Coatings Incorporated with Flame Spray Pyrolyzed Silica Modified via in-situ Route and ex-situ Route

A new type of transparent scratch resistant coatings including in-situ modified SiO2 （g-SiO2） in flame spray pyrolysis （FSP） process was prepared. The maximum content of g-SiO2 in the coating was 15 wt%, which is higher than that of SiO2 modified by traditional wet chemical route （I-SiO2, only 10 wt%）. The results of transmission electron microscopy have demonstrated that in-situ surface modified g-SiO2 particles dispersed well with smaller agglomerates in the final coating, which was much better than the particles modified via wet chemical route. Visible light transmittance and haze tests were introduced to characterize the optical quality of the films. All coatings were highly transparent with the visible light transmittance of above 80%, especially for coatings containing g-SiO2, which exhibited slightly higher visible light transmittance than l-SiO2 embedded one. The haze value of coatings incorporated with 15 wt% g-SiO2 was 1.85%, even lower than the coating with 5 wt% I-SiO2 （haze value of 2.09%）, indicating much better clarity of g-SiO2. The excellent optical property of g-SiO2 filled coatings was attributed to the good dispersion and distribution of particles. Nano-indention and nano-scratch tests were con- ducted to investigate the scratch resistance of coatings on nano-scale. The surface hardness of the coatings rose by 18% and 14%, and the average friction coefficient decreased by 15% and 11%, respectively, compared to the neat coat due to the addition of 10 wt% g-SiO2 and I-SiO2. The pencil hardness of the coating with 15 wt% g-SiO2 increased from 2B for the neat coating to 2H. However, the pencil hardness of coating with 10 wt% I-SiO2 was only H. The results showed that the g-SiO2 embedded coatings exhibited higher scratch resistance and better optical properties.

Evolution of Microstructure,Mechanical Properties and Corrosion Resistance of Ultrasonic Assisted Welded-Brazed Mg/Ti Joint

Ultrasonic vibration with different powers from 0 k W to 1.6 k W was applied during the tungsten inert gas welding-brazing of Mg/Ti.The microstructures,mechanical properties and corrosion resistance of the ultrasonic assisted tungsten inert gas（U-TIG） welded-brazed Mg/Ti joint were characterized.The results showed that,without being subjected to ultrasonic vibration,coarse columnar α-Mg grains occurred in the fusion zone of Mg/Ti joint.However,with ultrasonic power of 1.2 k W,the average grain size of columnar α-Mg grains was refined from 200 μm to about 50 μm and the tensile strength of joints increased^18% up to 228 MPa.Besides,high fraction of grain boundaries was introduced by grain refinement,contributing to improve the corrosion resistance in two ways：（i） accelerating the formation of Mg（OH）2protective layer and（ii） reducing the mismatch and disorder between Mg（OH）2 protective layer and Mg alloy surface.

Influence of Rare Earth(Ce and La) Addition on the Performance of Al-3.0 wt%Mg Alloy

The influences of rare earth elements（cerium and lanthanum） on the microstructure and phases of Al-3.0 wt%Mg alloys used for electromagnetic shielding wire were characterized by scanning electron microscopy（SEM）, energy-dispersive spectroscopy（EDS）, X-ray diffraction（XRD） and differential scanning calorimetry（DSC）. The mechanical properties and electrical resistivity were also investigated. The results indicated that a certain content of rare earth could improve the purification of the aluminum molten, enhance the strength, and reduce the electrical resistivity of Al-3.0 wt%Mg alloys. The strength reached the top value when RE content was 0.3 wt% while the alloy with 0.2 wt% RE addition had the smallest electrical resistivity. The elongation varied little when RE addition was no more than 0.2 wt%. But the excessive addition of rare earth would be harmful to the microstructure and properties of Al-3.0 wt%Mg alloys.

Resistive Switching Behavior of Ag/Mg0.2Zn0.8O/ZnMn2O4/p^+-Si Heterostructure Devices for Nonvolatile Memory Applications

The Ag/Mg0.2Zn0.8O/ZnMn2O4/p^＋-Si heterostructure devices were fabricated by sol-gel spin coating technique and the resistive switching behavior,conduction mechanism,endurance characteristic,and retention properties were investigated.A distinct bipolar resistive switching behavior of the devices was observed at room temperature.The resistance ratio R_（HRS）/RLRS of high resistance state and low resistance state is as large as four orders of magnitude with a readout voltage of 2.0 V.The dominant conduction mechanism of the device is trap-controlled space charge limited current（SCLC）.The devices exhibit good durability under 1×10^3cycles and the degradation is invisible for more than 10^6 s.