Effects of thermal-oxidative aging on rheological properties of montmorillonite modified bitumen

Organic montmorillonite(OMMT) modified bitumen nanocomposites was prepared by melt blending.The effects of thin-film oven test(TFOT) and pressure ageing vessel(PAV) on rheological properties of pristine bitumen and OMMT modified bitumen were investigated by dynamic shear rheometer(DSR).The results show that complex modulus(G*) increases,phase angle(δ) decreases and rutting factor(G*/sin δ) is enhanced for the pristine bitumen after TFOT,whereas G*,δ and G*/sin δ of OMMT modified bitumen have a little change before and after TFOT.Besides,the pristine bitumen exhibits a large increase of G* and a great decrease of δ after PAV aging.However,the changes in G* and δ of OMMT modified bitumen are small before and after PAV.Compared with the pristine bitumen,OMMT modified bitumen presents a lower fatigue factor(G*sin δ) after PAV.As a consequence,resistance to thermal-oxidative aging of bitumen is remarkably improved due to the introduction of OMMT.

Effect of Solutionizing and Aging on Microstructure and Mechanical Properties of Warm-rolled 7075 Alloy

The effect of solution and aging treatments on microstructure and mechanical properties of warm-rolled 7075 alloy was investigated via optical microscope,electron backscattered diffraction,transmission electron microscopy and tensile tests.The 7075 alloy was subjected to solution treatments at 450℃for 1 h(ST1),490℃ for 1 h(ST2)and 1.5 h(ST3).Three aging routes were carried out on samples from ST2:one-step(A1),two-step(A2),and three-step aging(A3).The experimental results show mainly recrystallized equiaxed grains in ST1 and ST3 state but a combination of elongated and equiaxed grains in ST2 condition.Three aged alloys have similar microstructures of sample ST2 while the recrystallization frequency gets decreased after aging.The least recrystallization fraction occurs in A2 state.Three aged 7075 alloys all possess enhanced strength and plasticity.Precipitates characterization reveals the maximum strength is achieved in A2 sample as the matrix precipitates are composed mainly of smallηand manyη′phases.Aging route A2 appears preferable to other two aging conditions for attaining a pretty excellent combination of strength and plasticity.

Influence of Non-Natural Ageing Temperature on the Microstructural Characteristics and Mechanical Properties of Cast Aluminum 6063 Alloy

This research considered the effect of non-natural aging on the microstructural characteristics and mechanical properties of as-cast aluminum 6063 alloys. The samples were developed through a sand casting process and machined into tensile and impact test samples before carrying out solution heat treatment at 550?C (0.83 Tm) on two parts of the samples while retaining one part as the control. The two parts were further divided into sets denoted A and B and were aged at 180?C (0.27 Tm) and 160?C (0.24 Tm), respectively, for 12 hours. The results showed that sample A has the optimal yield strength and ultimate tensile strength of 192 and 206 MPa, respectively. Likewise, the sample gave the highest impact strength value of about 9.63 J/mm2. The observed results were supported by the optical micrograph, which revealed that the sample has evenly dispersed precipitates in its microstructure. This is deemed responsible for the observed increase in strength of the sample.

Microstructure and Mechanical Properties of Al-11.3Zn-3.2Mg-1.3Cu-0.2Zr-0.1Sr-x Ti Extruded Aluminum Alloy with Different Aging Process

The influences of adding different amount of Ti(0%,0.39%,0.87%)and three kinds of difierent aging processes(T6,T6I6,RRA)on the microstructure and properties of Al-11.3Zn-3.2Mg-1.3Cu-0.2Zr-0.1Sr were investigated.Results show that an appropriate amount of Ti can effectively inhibit grain growth and thus achieve the efiect of grain refinement.The contribution of dislocation density and dislocation strengthening become the biggest when Ti content is 0.39%.At the same time,the intergranular corrosion depth is the lowest when Ti content is 0.39%.Among the three aging processes,the alloys reach the greatest hardness and tensile strength in T6I6.The biggest tensile strength reaches 716.77 MPa.However,when aging at RRA,the alloys obtain the greatest elongation,reaching 7.2%,as well as the good corrosion resistance.

Acceleration of aging behavior and improvement of mechanical properties of extruded AZ80 alloy through(10–12) twinning

The effects of pre-existing {10–12} extension twins on the precipitation behavior of an extruded AZ80 material during aging and on its mechanical properties after peak aging are investigated. The material containing {10–12} twins-which are formed by compression before aging(twinned material)-has a finer grain size and higher dislocation density than the extruded material. Although the peak hardnesses of the twinned and extruded materials are almost the same, the time to reach the peak hardness is considerably shorter in the former material than in the latter(4 h and 24 h, respectively). In the twinned material, the high dislocation density of the {10–12} twins promotes continuous precipitation, which results in the formation of numerous fine Mg17Al12precipitates within the twins in the early stage of aging.The formation of these continuous precipitates reduces the driving force for discontinuous precipitation, which consequently suppresses the formation and growth of coarse Mg17Al12precipitates at the grain boundaries. Despite its shorter peak-aging time, the 4 h-peak-aged twinned material shows higher tensile strength and elongation than the 24 h-peak-aged extruded material. These higher mechanical properties of the former material are attributed primarily to the presence of more abundant fine continuous precipitates, which are effective in strengthening the material, and less abundant coarse discontinuous precipitates, which can act as crack initiation sites. These results demonstrate that the introduction of {10–12} twins into wrought Mg–Al-based alloys can accelerate the Mg17Al12precipitation kinetics considerably and improve the strength and ductility of the peak-aged alloys simultaneously.

Effect of secondary aging on microstructure and properties of cast Al-Cu-Mg alloy

To obtain better comprehensive properties of cast Al-Cu-Mg alloys,the secondary aging(T6I6)process(including initial aging,interrupted aging and re-aging stages)was optimized by an orthogonal method.The microstructures of the optimized Al-Cu-Mg alloy were observed by means of scanning electron microscopy and transmission electron microscopy,and the properties were investigated by hardness measurements,tensile tests,exfoliation corrosion tests,and intergranular corrosion tests.Results show that the S phase andθ’phase simultaneously exist in the T6I6 treated alloy.Appropriately increasing the temperature of the interrupted aging in the T6I6 process can improve the mechanical properties and corrosion resistance of Al-Cu-Mg alloy.The optimal comprehensive properties(tensile strength of 443.6 MPa,hardness of 161.6 HV)of the alloy are obtained by initial aging at 180℃for 2 h,interrupted aging at 90℃for 30 min,and re-aging at 170℃for 4 h.

The aging behavior,microstructure and mechanical properties of AlN/AZ91 composite

Microstructure evolution and mechanical properties of the aging treated AlN/AZ91 composites were systematically investigated by optical microscopy(OM),high resolution scanning electron microscopy(HRSEM)with an energy dispersive spectrum(EDS),and high-angle annular dark field scanning transmission electron microscopy(HAADF-STEM).The results show that the higher fracture elongation(14±1%)and ultimate tensile strength(275±6 MPa)were simultaneously obtained in the peak-aged AlN/AZ91 composites.Comparied with AZ91 matrix alloy,the strength was increased by about 44%and the elongation was approximately five times higher,which mainly attributed to the precipitation of nano-sizedγ-Mg_(17)Al_(12)phase and the activation of non-basal slip systems induced by in-situ AlN particles at room temperature.However,the in-situ formation of AlN reinforcements consumed part of Al element in the matrix alloy,which resulted into the volume fraction decreasing ofγ-Mg_(17)Al_(12)precipitates,and then the age hardening and strengthening efficiency were reduced in the AlN/AZ91 composites.On the other hand,the mismatch of thermal expansion coefficient between AlN particles and AZ91 matrix generated high density dislocations around AlN particles,which promoted the precipitation ofγ-Mg_(17)Al_(12)phase,and then the peak aging time and temperature were decreased.

Effect of Organophilic Montmorillonite on Thermal-oxidative Aging Behavior of SBS Modified Bitumen Crack Filling Material

Styrene-butadiene-styrene （SBS） modified bitumen crack filling material with organophilic montmorillonite （OCFM） was prepared by melt blending. X-ray diffraction analysis shows that the interlayer spacing of organophilic montmorillonite （OMMT） in OCFM is widened and an exfoliated structure may be formed. Thermal-oxidative aging behavior of OCFM and SBS modified bitumen crack filling material （SCFM） was investigated. The experimental results indicate that the rate of thermal-oxidative aging of OCFM is much slower than that of SCFM, which can be attributed to barrier of exfoliated structure of OCFM to oxygen.

Ag元素和时效时间对T6态Al-5Cu-0.8Mg-0.15Zr-0.2Sc合金拉伸性能的影响

为了明确Ag元素的添加对Al-Cu-Mg系铝合金拉伸性能的影响,针对T6态(固溶+时效处理)的热挤压Al-5Cu-0.8Mg-0.15Zr-0.2Sc(-0.5Ag)合金进行了室温和高温拉伸实验。结果表明,添加0.5%Ag元素可显著提高T6态Al-5Cu-0.8Mg-0.15Zr-0.2Sc合金的室温抗拉强度、屈服强度、峰时效态及该合金在150~300℃范围的抗拉强度和屈服强度,但会降低该合金的室温和高温塑性。断口形貌的扫描电子显微镜观察与分析结果表明,在室温及高温拉伸加载条件下,T6态Al-5Cu-0.8Mg-0.15Zr-0.2Sc(-0.5Ag)合金的拉伸断口上大部分存在韧窝和撕裂棱,表现出明显的韧性断裂特点。

Ag(Ⅰ)与氯苯基苯并咪唑配合物的合成、圆二色性和荧光性质

本文合成了Ag(Ⅰ)与2-(o-氯苯基)苯并咪唑(OCBM)的配合物,采用元素分析、质谱、UV、IR、摩尔电导率等手段进行了表征。圆二色性研究发现,配合物在199nm处呈正科顿效应,而在208nm和247nm处呈负科顿效应。荧光性质研究表明,配合物的特征荧光发射峰出现在601nm和613nm处,荧光寿命τ601和τ613分别为0.40ns和0.35ns。Ag(Ⅰ)配合物可发射橙色荧光和红色荧光,是良好的荧光材料。

Microstructure and Properties of Cu-Cr-Zr Alloy after Rapidly Solidified Aging and Solid Solution Aging

The structure and properties of Cu-Cr-Zr alloy were studied after rapidly solidified aging and solid solution aging.At the early stage of aging （500℃ for 15 rain）, the hardness and the conductivity of the alloy rapidly solidified are 143 HV and 72% IACS, respectively. Under the same aging condition, the hardness and electrical conductivity of the alloy solid solution treated can reach 86 HV and 47% IACS, respectively. The microstructure was analyzed, and the grain size after rapid solidification is much smaller than that after solid solution treatment. By rapidly solidified aging the fine precipitates distribute inside the grains and along the grain boundary, while by solid solution aging there are large Cr particles along the grain boundary.

Effects of aging treatment and heat input on the microstructures and mechanical properties of TIG-welded 6061-T6 alloy joints

Aging treatment and various heat input conditions and mechanical properties of TIG welded 606I-T6 alloy joints were adopted to investigate the microstructural evolution by microstructural observations, microhardness tests, and tensile tests. With an increase in heat input, the width of the heat-affected zone （HAZ） increases and grains in the fusion zone （FZ） coarsen. Moreover, the hardness of the HAZ decreases, whereas that of the FZ decreases initially and then increases with an increase in heat input. Low heat input results in the low ultimate tensile strength of the welded joints due to the presence of partial penetrations and pores in the welded joints. After a simple artificial aging treatment at 175℃ for 8 h, the microstructure of the welded joints changes slightly. The mechanical properties of the welded joints enhance significantly after the aging process as few precipitates distribute in the welded seam.

Effects of aging on the microstructures and mechanical properties of extruded AM50+xCa magnesium alloys

The effects of aging treatment on the microstructures and mechanical properties of extruded AM50 ＋ xCa alloys （x=0, 1, 2 wt.%） were studied. The results indicated the secondary phase Mgl7Al12 precipitated from the saturated α-Mg solid solution while Al2Ca changed slightly when the aging time was increased. The hardness of extruded AM50 ＋ xCa al- loys increased initially to its peak, and then dropped to reach its original hardness with the increase in aging time. With the increase in aging temperature, the hardness of the AM50 ＋ 2Ca ahoy decreased, whereas the hardness of AM50 and AM50 ＋ 1Ca alloys decreased in the initial stages of aging treatment and increased in the later stages of aging treatment. The tensile strengths of AM50 and AM50 ＋ 1Ca alloys increased after aging treatment for the precipitation of Mg17Al12 phase, which increases the resistance against dislocation movement at the grain boundary; with increase in aging temperature, their tensile strengths increased. For AM50 ＋ 2Ca alloy, the tensile strength declined after aging at 150℃ and 175℃, while it increased slightly at 200℃. The ductility of AM50 ＋ xCa alloys （x = 0, 1, 2 wt.%） declined after aging treatment.

Effect of natural aging on microstructure and mechanical properties of friction stir welded 7050-T7451 joints

The microstructure and mechanical properties of friction stir welded 2. 5 mm 7050-T7451 aluminum alloy natural aging 72 h and 17 520 h were investigated, respectively. The uniaxial tensile test showed that yield strength, tensile strength and elongation of the joints 17 520 h natural aging were about 20%, 12% and 24% higher than those joints natural aging 72 h. Hardness profile of natural aging 17 520 h joint witnessed significant enhancement in nugget zone, compared with 72 h natural aging. Differential scanning calorimetry （ DSC ） and transmission electron microscopy （TEM） test revealed that more Guinier-Preston zone, η＇ and 71 phase emerged in nugget zone as natural aging duration increased, high density of dislocation located within grain boundary in nugget zone of joints natural aging 72 h. It is concluded that natural aging was feasible to enhalwe strength and plasticity of FSW joints simultaneously.

Effect of pre-deformation on microstructure and mechanical properties of WE43 magnesium alloy II: Aging at 250 and 300℃

In this work,the microstructural evolution and mechanical properties of a pre-deformed WE43 magnesium alloy when aged at 250 and 300℃ were further investigated.It is found that the abundant deformation twins introduced by pre-deformation were maintained within the alloy during the aging treatment.Second particles formed at the twin boundaries and coarsened with aging time,especially at 300℃.When peak-aged at 250℃,the fine metastable β'''and β' precipitates formed in the un-deformed alloy have been transformed into relatively large β1 and β precipitates by the pre-deformation.While peak-aged at 300℃,the pre-deformation obviously refined the β precipitates.Mechanical properties indicate that pre-deformation can increase the yield strength by 19MPa and 54MPa for the peak-aged alloy at 250℃ and 300℃,respectively,and will not obviously deteriorate the tensile elongations.

Effect of Ultraviolet Aging on the Bonding and Tensile Properties of Polymer-Cement Composite

In this paper,the specimens of polymer-cement composites after 1 d,7 d,15 d,and 30 d aging without aging and UV aging are subjected to fixed extension test and tensile test.By observing the mode of the composite in the fixed-elongation test,and measuring the elastic recovery rate,tensile strength,elongation at break,peak tensile strain,tensile toughness and pre-peak tensile toughness of the composite,the effects of UV aging on the bonding and the tensile properties of the composite were studied.And combining with scanning electron microscopy experiments,the micro-mechanism of the effect of ultraviolet aging on the properties of composite was analyzed.The results showed that the composite had a good bonding property,and no damage was observed after UV aging for 30 days.The UV aging increased the elastic recovery rate and peak tensile within a certain range.The elastic recovery rate and peak tensile strain of the composite increased by 6.60%and 23.55%respectively after UV aging for 15 days.Therefore,the UV aging could enhance the tensile property and the tensile energy consumption performance of the composite.The tensile strength of the composite increased by 65.36%after UV aging for 30 days.The tensile toughness and pre-peak tensile toughness of the composite were increased by 43.29%and 101.83%respectively after UV aging for 15 days.The elongation at break of composite decreased continuously after UV aging due to the photo-oxygen reaction,as well as secondary hydration reaction and cross-linking curing reaction of cement.

Effect of Hydration Aging and Water Binder Ratio on Microstructure and Mechanical Properties of Sprayed Concrete

In order to study the durability of sprayed concrete （shotcrete）, effects of different hydration aging and water-binder ratio （w/b） on the microstructure of cement paste and basic mechanical properties of test specimens were investigated. The phase composition, mass percentage of ettringite and portland in hydration production and microstructure were characterized by X-ray diffraction （XRD）, thermo gravimetry-differential scanning calorimetry （TG-DSC） and scanning electron microscopy （SEM）, respectively. The experimental results showed that changes in phase composition was more significant than those of water-binder ratio. With hydration aging and water-binder ratio increased, the mass percentage of ettringite and portland was decreased from 4.42%, 1.49% to 3.31%, 1.35%, respectively and the microstructure of paste was significantly compacted. Likewise, the mechanical properties including cubic compressive strength and splitting tensile strength were rised obviously.

STUDY ON REDUCING THE CORE LOSS OF GRAIN ORIENTED SILICON STEEL AND IMPROVING ITS AGING PROPERTY BY LASER NITRIDING TECHNIQUE IN ATMOSPHERIC AMBIENT

CW-CO2 laser nitriding technique was applied to improve the properties （such as aging property and the core loss） of grain oriented silicon steel. The samples were nitrided with regular space. Laser power density and scanning speed were chosen as 7.8×10^5W·cm^-2 and 100mm·min^-1. By some laser irradiation, Fe4N and Fe3N were formed in the nitrided zone. The nitrided samples were annealed at the temperatures ranged from 100 to 90℃. The core loss of some interested samples was tested. The results show that the core loss of the nitrided samples with different thickness of 0.23 and 0.30mm decreased by 14.9% and 9.4% respectively, and the aging property were improved up to 800℃. The mechanism of laser nitriding to improve the properties of grain oriented silicon steel is discussed.

Effects of postweld aging on the microstructure and properties of bobbin tool friction stir-welded 6082-T6 aluminum alloy

Samples of 6082-T6 aluminum alloy were subjected to bobbin tool friction stir welding (BT-FSW), and the joints were treated by postweld natural aging (PWNA) and postweld artificial aging (PWAA). The microstructure, microhardness, and tensile properties of the aged and as-welded specimens were investigated. Transmission electron microscopy (TEM) observations revealed that a large number of Guinier–Preston (GP) zones precipitated in the form of a network on the stir zone (SZ) after PWNA for 60 d, and a large number of β'' phases precipitated in the matrix for after PWAA for 6 h. As the aging time increased, the microhardness of the SZ and the thermomechanically affected zone (TMAZ) increased significantly, and the hardness of the SZ after PWAA for 6 h was close to that of the base metal (BM). With increasing PWNA time, the strength and strain increased slightly. When the PWAA time increased, the strength clearly increased, with a maximum value of 279.9 MPa after 6 h, while the strain decreased.

MICROSTRUCTURE AND MECHANICAL PROPERTIES OF Fe-Ni-Co-BASE SUPERALLOY AFTER LONGTERM AGING AT 650℃

The microstructure and mechanical properties of a Ni-Fe-Co base superalloy with low thermal expansion coefficient after aging at 650℃ for 200,500,1000 and 2000 h have been investigated.It was found that they are stable at 650℃.This alloy is believed to.fill the re- quirements for long time service to aircraft engine.