High Temperature Rheological Performance of Graphene Modified Rubber Asphalt

To elucidate the high temperature rheological capability of graphene modified rubber asphalt,three contents of graphene and crumb rubber were prepared by a combination of mechanical agitation and high speed shearing machine,then used dynamic shear rheological test(DSR)and multiple stress creep recovery(MSCR)tests to evaluate.The hardness and softening point with rotational viscosity of samples raised with the addition of graphene,especially the addition of 0.04%.Dynamic shear rheological test revealedthat the dynamic shear modulus G*,rutting factor G*/Sin δ,and zero shear viscosity(ZSV)of graphene-modified rubber asphalt were greatly influenced along with graphene-increased,on the contrary,phase angle δ which characterize the viscoelastic ratio of asphalt decreased.Multiple stress creep recovery(MSCR)tests showed that the graphene-enhanced rubber asphalt had high-temperature stability through non-recoverable creep compliance(Jnr).Based on these findings,graphene-modified rubber asphalt binders with the addition of 0.04% graphene had good viscoelastic properties as well as high temperature rutting resistance performance.In the meantime,G*/Sin δ,ZSV,and Jnr100,Jnr3200 have good correlation,which can reveal the excellent high-temperature stability performance of asphalt.

Wire arc additive manufacturing of a heat-resistant Al-Cu-Ag-Sc alloy:microstructures and high-temperature mechanical properties

With a high energy efficiency,low geometric limitation,and low cracking susceptivity to cracks,wire arc additive manufacturing(WAAM)has become an ideal substitute for casting in the manufacturing of load-bearing high strength aluminum components in aerospace industry.Recently,in scientific researches,the room temperature mechanical performance of additive manufactured high strength aluminum alloys has been continuously broken through,and proves these alloys can achieve comparable or even higher properties than the forged counterpart.Since the aluminum components for aerospace usage experience high-low temperature cycling due to the absence of atmosphere protection,the high temperature performances of additive manufactured high strength aluminum alloys are also important.However,few research focuses on that.A special 2319Ag Sc with 0.4 wt.%Ag and 0.2 wt.%Sc addition designed for high temperature application is deposited successfully via cold metal transfer(CMT)based on WAAM.The microstructures and high temperature tensile properties are investigated.The results show that the as-deposited 2319Ag Sc alloy presents an alternate distribution of columnar grains and equiaxed grains with no significant textures.Main second phases are Al_(2)Cu and Al3Sc,while co-growth of Al_(2)Cu and bulk Al_(3)Sc is found on the grain boundary.During manufacturing,nanoscale Al_(2)Cu can precipitate out from the matrix.Ag and Mg form nano-scaleΩphase on the Al_(2)Cu precipitates.At 260℃,average yield strengths in the horizontal direction and vertical direction are 87 MPa±2 MPa,87 MPa±4 MPa,while average ultimate tensile strengths are 140 MPa±7 MPa,141 MPa±11 MPa,and average elongations are 11.0%±2.5%,13.5%±3.0%.Anisotropy in different directions is weak.

High-temperature properties and microstructure of Mo microalloyed ultra-high-strength steel

The high-temperature mechanical properties and microstructure of forging billets of C-Si-Mn-Cr and C-Si-Mn-Cr-Mo ultra-high-strength cold-rolled steels（tensile strength≥1000 MPa,elongation≥10%） were studied.Through the comparison of reduction in area and hot deformation resistance at 600-1300°C,the Mo-containing steel was found to possess a higher strength and a better plasticity than the Mo-free one.The equilibrium phase diagram and atom fraction of Mo in different phases at different temperatures were calculated by Thermo-Calc software（TCW）.The results analyzed by using transmission electron microscopy and TCW show that precipitates in the Mo-containing steel are primarily M23C6,which promote pearlite formation.The experimental data also show that a lower ductility point existing in the Mo-free steel at 850°C is eliminated in the Mo-containing one.This is mainly due to the segregation of Mo at grain boundaries investigated by electron probe microanalysis（EPMA）,which improves the strength of grain boundaries.

High-temperature mechanical properties of near-eutectoid steel

The high-temperature mechanical properties of near-eutectoid steel were studied with a Cleeble-1500 simu- lation machine. Zero strength temperature （ZST）, zero ductility temperature （ZDT）, hot ductility curves, and strength curves were measured. Two brittle zones and one plastic zone were found in the temperature range from the melting point to 600℃. Embrittlement in zone I is caused by the existence of liquid film along dendritic interfaces. Ductility loss in zone Ⅲ mainly results from precipitates and inclusions as well as S segregation along grain boundaries. Pearlite transformation also accounts for ductility deterioration in the temperature range of 700-600℃. Moreover, the straightening temperature of the test steel should be higher than 925℃ for avoiding the initiation and propagation of surface cracks in billets.

High Temperature Properties of Discontinuously Reinforced Titanium Matrix Composites:A Review

Further improvement on high temperature durability is one of the most important aims except for high specific strength, high specific stiffness, and excellent wear resistance, to design and fabricate discontinuously reinforced titanium matrix composites （DRTMCs）. Their superior properties render them extensive application potential in aerospace and military industries due to the urgent demand for the materials with characteristics of lightweight, high strength, high stiffness and high temperature durability. With development on fabrication methods and room temperature properties, testing, characterizing, evaluating and further increasing high temperature properties of DRTMCs are becoming more and more important to promote their applications. This review provides insights and comprehensions on the high temperature tensile properties, superplastic tensile properties, creep behaviors, and high temperature oxidation behaviors of DRTMCs,

High temperature thermoelectric properties of highly c-axis oriented Bi_2Sr_2Co_2O_y thin films fabricated by pulsed laser deposition

High-temperature thermoelectric transport property measurements have been performed on the highly c-axis oriented Bi2Sr2Co20v thin films prepared by pulsed laser deposition on LaA1Oa （001）. Both the electric resistivity p and the seebeck coefficient S of the film exhibit an increasing trend with the temperature from 300 K-1000 K and reach up to 4.8 m. cm and 202 V/K at 980 K, resulting in a power factor of 0.85 mW/mK which are comparable to those of the single crystalline samples. A small polaron hopping conduction can be responsible for the conduction mechanism of the film at high temperature. The results demonstrate that the Bi2Sr2Co2Oy thin film has potential application has high temperature thin film thermoelectric devices,

Effect of Lanthanum on Mechanical Properties of ZL702 Alloy at Room and High Temperature Condition

Effects of lanthanum on microstructure and mechanical properties of ZL702 alloy at room and high temperature conditions are studied. The experiment shows that high temperature intermetallics reticularly distributing at grain boundary are formed with La and Al, Si, Fe etc. elements of alloy, which enhances the thermal stability of the alloy. With appropriate content of La (0.10%～ 0.15%), the mechanical properties of the alloy, such as strength, at room temperature and high temperature can be improved.

Mechanical Properties with High Temperature and the Microstructure of Carbon/Phenolic Ablative Composites

Carbon fiber reinforced phenolic based composites were prepared by laminating molding. The variation in mechanical characteristics of composites was evaluated with heating temperature and procedure. The microstructures of composites at different temperatures were observed by optical microscope and scanning electron microscope, respectively. The results showed that the main weight loss range of carbon/phenolic is from 300 to 800 ℃, before 700 ℃ the weight loss was resulted from pyrolysis and after that the weight loss was mainly by oxidation in the fiber phase; with the heat treatment temperature rising, the bonding at the interface of carbon fibers and resin matrix weakened; in the pyrolysis temperature range, the interlaminar shear strength（ILSS） of carbon/phenolic showed a rapid drop with temperature rising, and then decrease in the rate of ILSS became relatively slower; the fiber oxidation had little influence on the ILSS.

High temperature mechanical properties of low carbon silicon-bearing steel by twin-roll strip casting

The tensile equipment of the advanced confocal scanning laser microscope （CSLM） was used to research the high temperature mechanical properties of low carbon silicon-bearing steel by twin-roll strip casting. The results show that, at the strain rate of 0. 000 5 s ^-1, the strip clearly shows signs of brittleness at around 600 ℃ and its plasticity falls considerably between 750 ℃ and 600 ℃. This is because during the transformation from austenite to ferrite, the low strength ferrite at the austenite grain boundaries greatly reduces the steel＇ s high temperature plasticity. The subsequent strip coiling process should be controlled at less than the brittle temperature of approximately 600 ℃, so cracks at the coiling stage can be prevented.

Studies of electrical properties of rocks under high temperature and pressure

Studies of the rocks′ electrical properties under high temperature and pressure have found favors in the geophysicist′s eyes, because those studies are becoming to be the important methods to understand the earth′s interior materials, their migration and evolution. This article introduces the development and significant of those studies from the measurements, instruments and affections, etc .

High-temperature performance prediction of iron ore fines and the ore-blending programming problem in sintering

The high-temperature performance of iron ore fmes is an important factor in optimizing ore blending in sintering. However, the application of linear regression analysis and the linear combination method in most other studies always leads to a large deviation from the desired results. In this study, the fuzzy membership functions of the assimilation ability temperature and the liquid fluidity were proposed based on the fuzzy mathematics theory to construct a model for predicting the high-temperature performance of mixed iron ore. Comparisons of the prediction model and experimental results were presented. The results illustrate that the prediction model is more accurate and effective than previously developed models. In addition, fuzzy constraints for the high-temperature performance of iron ore in this research make the results of ore blending more comparable. A solution for the quantitative calculation as well as the programming of fuzzy constraints is also introduced.

Elevated temperature endurance and creep properties of extruded 2D70 Al alloy rods

The elevated temperature performances of 2D70 Al alloy hot extrusion rods after two-stage homogenization and intensive deformation were studied by measuring the elevated temperature enduring strength and the creep ultimate strength. The fracture morphology of some selected samples after testing at different elevated temperatures was observed by scanning electron microscopy （SEM）. The results indicate that, as the test temperature increases, the elevated temperature enduring strength of 2D70 Al alloy decreases gradually. In a comparison between 150 C and 240 C, the notch enduring strength drops from 375 to 185 MPa and the smooth enduring strength drops from 337 to 130 MPa. Enduring strength is not sensitive to the notch. The notch sensitivity ratio （NSR） coefficient is in the range of 1.119 to 1.423 from 150 C to 240 C. The creep test results show that, as the test temperature increases from 150 C to 240 C, the creep ultimate strength of 2D70 Al alloy rods drops gradually from 312 to 117 MPa.

High-temperature frictional wear behavior of MCrAlY-based coatings deposited by atmosphere plasma spraying

Al2O3-r2O03/NiCoCrAIYTa coatings were prepared via atmosphere plasma spraying （APS）. The microstructure and phase com- position of the coatings were analyzed by X-ray diffraction （XRD）, scanning electron microscopy （SEM）, laser confocal scanning microsco- py （LSCM）, and transmission electron microscopy （TEM）. The dry frictional wear behavior of the coatings at 500℃ in static air was inves- tigated and compared with that of 0Cr25Ni20 steel. The results show that the coatings comprise the slatted layers of oxide phases, unmelted particles, and pores. The hot abrasive resistance of the coatings is enhanced compared to that of 0Cr25Ni20, and their mass loss is approxi- mately one-fifteenth that of 0Cr25Ni20 steel. The main wear failure mechanisms of the coatings are abrasive wear, fatigue wear, and adhe- sive wear.

High temperature mechanical behavior of low-pressure sand-cast Mg-Gd-Y-Zr magnesium alloy

The aim of this work is firstly to optimize T6 heat-treatment of low-pressure sand-cast Mg-10Gd-3Y-0.5Zr alloy,and then systematically investigate the mechanical behavior of the T6-treated alloy from room temperature to 300℃.It turned out that the optimum T6 heat-treatments for the tested alloy are 525℃×12 h+225℃×14 h and 525℃×12 h+250℃×12 h which integrated age-hardening and tensile properties into account,respectively.The strength of the T6-treated alloy indicates obvious anomalous temperature dependence from room temperature to 300℃,namely both ultimate tensile strength and yield strength of the tested alloy firstly increase with tensile temperature,and then decrease as temperature increases further.Elongation increased with temperature monotonously.The tensile fracture mode of the tested alloy changes from transgranular fracture to intergranular fracture with the increasing of test temperature.

High temperature mechanical behaviour of Mg-6Zn-1Y alloy with 1 wt.% calcium addition:Reinforcing effect due to I-(Mg3Zn6Yi)and Mg6Zn3Ca2 phases

The infiuence of small calcium additions on the high-temperature mechanical behaviour in an extruded Mg-6Zn-l Y(wt.%)alloy reinforced by the I-phase has been investigated.Calcium promotes the formation of the intermetallic Mg6Zn3Ca2 phase instead of 1-phase,which results in a noticeable improvement of the yield strength and ultimate tensile strength of the alloy above 100℃.The strength of the alloys was analysed taking into account the contribution due to the grain size,the crystallographic texture and the volume fraction and nature of second phase particles.In situ synchrotron radiation diffraction experiments have been used to evaluate the load partitioning between the magnesium matrix and the second phase particles(1-and MgeZgCa?phases)in both alloys.The load transfer from the magnesium matrix towards the MgeZihCa?phase is markedly more effective than that for the I-phase over the entire temperature range,especially at 200°C,temperature at which the reinforcement effect of the I-phase is null.

Effect of the precipitation state on high temperature tensile and creep behaviors of Mg-15Gd alloy

Due to the effective precipitation strengthening effect of the β phase, Mg-Gd alloys exhibit excellent room temperature mechanical behaviors. However, when served at high temperatures, the metastable β phase will transform to other phases, resulting in severe performance degradation. In this study, we investigated the effect of precipitation state achieved by different heat treatments on high temperature tensile and creep behaviors of the Mg-15Gd alloy by comparing the properties of the as-cast, solid-solutioned(T4) and peak-aged(T6) alloys. The results showed that the tensile mechanical properties of the T6 alloy were always highest from room temperature to 300 ℃, in spite of an abnormal strength increase with temperature existed in the T4 alloy. For tensile creep properties, the T6 alloy exhibited the lowest steady creep rate below 235 ℃ while the T4 alloy possessed the best properties above 260 ℃. Microstructure characterization revealed that the transition was caused by the stress-promoted precipitation of β phase in the T4 alloy and rapid phase transformation in the T6 alloy at high temperatures. At 260 ℃, the calculated stress exponent n was 3.1 and 2.8 for the T4 and T6 alloys, respectively, suggesting the creep deformation mechanism was dislocation slip, which was further confirmed by the microstructure after creeping. Our findings can provide new insights into the heat treatment process of Mg-Gd alloys served at high temperatures.

Sensitivity to Stress Concentration of Steel at High Temperature

A new experimental method was developed to simulate the generation of the surface transversal crack on the continuous casting slab with a discontinuous sample. A high temperature property of steel named"the sensitivity to the stress concentration of steel at high temperature"was defined to evaluate the effect of stress concentration on thermal plasticity of steel. "The sensitivity parameter to the stress concentration of steel at high temperature"was available to determine the temperature range in which steel is sensitive to the stress concentration.

Microstructural characterization and mechanical properties of self-reinforced Si_3S_4 ceramics containing high oxynitride glass

Self-reinforced Si_3N_4 ceramics containing high oxynitride glass have been fabricated by the control of microstructure evolution and β-Si_3N_4 grain growth. The effects of the size distribution of the elongated β-SiaN_4 grains, and the β-Si_3N_4 grain growth as well as the oxynitride glass chemical characteristic on the microstructure and mechanical properties were investigated. The experimental results show that the β-Si_3N_4 grains in high oxynitride glass grow to elongated rod-like crystals and form the stereo-network structure. Under the sintering conditions of 1800℃ and 60 min, a quite uniform microstructure with an average aspect ratio of 6.5 and an average of 1 μm can be obtained. A large amount of oxynitride glass phase with high nitrogen content enhances the elevated temperature fracture toughness because of its high softening temperature and high viscosity. In the present material, the crack deflection and pullout of the elongated rod-like β-Si_3N_4 grains are the primary toughening mechanisms.

High Temperature Tensile Property and Fracture Behavior of Directionally Solidified Fe-Al-Ta Eutectic Composites

Fe-Al-Ta eutectic composites with solidification rates of 6,20,30,80 and 200μm/s were obtained by a modified Bridgman directional solidification technique and alloying.Moreover,tensile property and fracture behavior of Fe-Al-Ta eutectic composites were studied at 600℃.The relationship between mechanical property and microstructure at high temperature was studied.Microstructure of Fe-Al-Ta eutectic is composed of Fe_(2)Ta(Al)Laves phase and Fe(Al,Ta)matrix phase.In addition,the tensile strength at high temperatures is higher than that at room temperature.The tensile strength is increased with the increase of solidification rate.Moreover,fracture morphology transforms from cleavage fracture to dimple fracture as the solidification rate is increased at high temperatures.

Effect of Y_(2)O_(3) on microstructure and properties of CoCrFeNiTiNb high entropy alloy coating on Ti-6Al-4V surface by laser cladding

The effects of Y_(2)O_(3) on the microstructure, microhardness, wear resistance, high-temperature oxidation resistance, hot corrosion resistance, and electrochemical corrosion behaviour of CoCrFeNiTiNb high entropy alloy coatings formed on Ti-6Al-4V alloy surfaces were studied. The results show that the addition of Y_(2)O_(3) changes the proportion of the phase but does not change its type. The average grain size is only 1/4.7 of that of the high entropy alloy(HEA) coating, and the fine-grained strengthening leads to increases in the microhardness and wear resistance of 21.8% and 26.9%, respectively. The addition of Y_(2)O_(3) enhances the denseness and bonding properties of the oxide and corrosion product layers, reducing the oxidation and hot corrosion rates by 60.3% and 40.3%, respectively. The addition of Y_(2)O_(3) doubles the corrosion resistance which is attributed to the refinement of the grains, the increased proportion of HCP and TiN, and the weakening of galvanic coupling corrosion.