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.

Evolution of mechanical properties,localized corrosion resistance and microstructure of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging

The evolution of mechanical properties,localized corrosion resistance of a high purity Al-Zn-Mg-Cu alloy during non-isothermal aging(NIA)was investigated by hardness test,electrical conductivity test,tensile test,intergranular corrosion test,exfoliation corrosion test,slow strain rate tensile test and electrochemical test,and the mechanism has been discussed based on microstructure examination by optical microscopy,electron back scattered diffraction,scanning electron microscopy and scanning transmission electron microscopy.The NIA treatment includes a heating stage from 40℃to 180℃with a rate of 20℃/h and a cooling stage from 180℃to 40℃with a rate of 10℃/h.The results show that the hardness and strength increase rapidly during the heating stage of NIA since the increasing temperature favors the nucleation and the growth of strengthening precipitates and promotes the transformation of Guinier-Preston(GPI)zones toη'phase.During the cooling stage,the sizes ofη'phase increase with a little change in the number density,leading to a further slight increase of the hardness and strength.As NIA proceeds,the corroded morphology in the alloy changes from a layering feature to a wavy feature,the maximum corrosion depth decreases,and the reason has been analyzed based on the microstructural and microchemical feature of precipitates at grain boundaries and subgrain boundaries.

Effect of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy

The effects of interrupted aging on mechanical properties and corrosion resistance of 7A75 aluminum alloy extruded bar were investigated through various analyses,including electrical conductivity,mechanical properties,local corrosion properties,and slow strain rate tensile stress corrosion tests.Microstructure characterization techniques such as metallographic microscopy,scanning electron microscopy(SEM),and transmission electron microscopy(TEM)were also employed.The results indicate that the tensile strength of the alloy produced by T6I6 aging is similar to that produced by T6I4 aging,and it even exceeds 700 MPa.Furthermore,the yield strength increases by 52.7 MPa,reaching 654.8 MPa after T6I6 aging treatment.The maximum depths of intergranular corrosion(IGC)and exfoliation corrosion(EXCO)decrease from 116.3 and 468.5μm to 89.5 and 324.3μm,respectively.The stress corrosion factor also decreases from 2.1%to 1.6%.These findings suggest that the alloy treated with T6I6 aging exhibits both high strength and excellent stress corrosion cracking resistance.Similarly,when the alloy is treated with T6I4,T6I6 and T6I7 aging,the sizes of grain boundary precipitates(GBPs)are found to be 5.2,18.4,and 32.8 nm,respectively.The sizes of matrix precipitates are 4.8,5.7 and 15.7 nm,respectively.The atomic fractions of Zn in GBPs are 9.92 at.%,8.23 at.%and 6.87 at.%,respectively,while the atomic fractions of Mg are 12.66 at.%,8.43 at.%and 7.00 at.%,respectively.Additionally,the atomic fractions of Cu are 1.83 at.%,2.47 at.%and 3.41 at.%,respectively.

Effect of Accelerated Aging Temperature under Artificial Seawater on the Properties of Carbon Fiber/Epoxy Composites and the Erosion Mechanism

In order to explore the effect of artificial accelerated aging temperature on the performance of carbon fiber/epoxy resin composites,we used artificial seawater as the aging medium,designed the aging environment of seawater at different temperatures under normal pressure,and studied the aging behavior of carbon fiber/epoxy composites.The infrared spectroscopy results show that,with the increase of aging temperature,the degree of hydrolysis of the composite is greater.At the same time,after 250 days of aging of artificial seawater at regular temperature,40 and 60 ℃,the moisture absorption rates of composite materials were 0.45%,0.63%,and 1.05%,and the retention rates of interlaminar shear strength were 91%,78%,and 62%,respectively.It is shown that the temperature of the aging environment has a significant impact on the hygroscopic behavior and mechanical properties of the composite,that is,the higher the temperature,the faster the moisture absorption of the composite,and the faster the decay of the mechanical properties of the composite.

Microstructure and mechanical properties stability of pre-hardening treatment in Al-Cu alloys for pre-hardening forming process

The stability of the microstructure and mechanical properties of the pre-hardened sheets during the pre-hardening forming(PHF)process directly determines the quality of the formed components.The microstructure stability of the pre-hardened sheets was in-vestigated by differential scanning calorimetry(DSC),transmission electron microscopy(TEM),and small angle X-ray scattering(SAXS),while the mechanical properties and formability were analyzed through uniaxial tensile tests and formability tests.The results in-dicate that the mechanical properties of the pre-hardened alloys exhibited negligible changes after experiencing 1-month natural aging(NA).The deviations of ultimate tensile strength(UTS),yield strength(YS),and sheet formability(Erichsen value)are all less than 2%.Also,after different NA time(from 48 h to 1 month)is applied to alloys before pre-hardening treatment,the pre-hardened alloys possess stable microstructure and mechanical properties as well.Interestingly,with the extension of NA time before pre-hardening treatment from 48 h to 1 month,the contribution of NA to the pre-hardening treatment is limited.Only a yield strength increment of 20 MPa is achieved,with no loss in elongation.The limited enhancement is mainly attributed to the fact that only a limited number of clusters are transformed into Guinier-Preston(GP)zones at the early stage of pre-hardening treatment,and the formation ofθ''phase inhibits the nucleation and growth of GP zones as the precipitated phase evolves.

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.

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.

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.

Effects of the two-step ageing treatment on the microstructure and properties of 7B04 alloy pre-stretched thick plates

The effects of the two-step ageing parameters （temperature and time） on the mechanical properties and electrical conductivity of 7B04 （A1-Zn-Mg-Cu） pre-stretched thick plates were studied. The results reveal that the initial T1 ageing contributes a major increase of the tensile strength, and the 0.2% proof stress value reaches 482 MPa after ageing for 7 h at 115℃. Behavioral differences in the tensile properties of the alloy after the two-step ageing treatment were less with the first-step ageing at 115~C for different time periods （7, 14, and 21 h）. The effects of the second ageing parameters on the properties and microstructure of the 7B04 alloy were remarkable. TEM analysis of the samples aged at Temper I （7 h at 115℃ ＋ 12 h at 160℃） and Temper II （7 h at 115℃ ＋ 16 h at 165℃） indicates that two kinds of phases, i.e. 11＇ and 11 phases, precipitate from the matrix and efficiently improve the tensile strength of the alloy, and the grain boundary precipitates are coarse and discrete. There are obvious precipitate free zones （PFZs） along the grain boundary in the microstructure of the alloy after the two-step ageing treatment.

Effect of ageing on fatigue properties of asphalt

The fatigue properties of asphalts were investigated after various laboratory simulation ageing tests and outdoor natural exposure ultraviolet radiation ageing,by dynamic shear rheometer(DSR) time sweep fatigue test in constant strain model and a new type of specimen which was introduced to avoid the problem of adhesion failure between rotor and asphalt binder.The results show that outdoor natural exposure ageing(NEA) causes the decrease of retained fatigue life distinctly,and photodegradation caused by outdoor NEA of 1 250 μm thin films asphalt for three months,is found to be severer than pressure ageing vessel(PAV) with respects to retained fatigue life.The effect of photodegradation increases as the time of outdoor NEA increases.DSR time sweep fatigue test in constant strain indicates that the aged styrene-butadiene-styrene(SBS) modified asphalt still displays better fatigue properties than the corresponding base asphalt after ageing.

Effects of interrupted ageing and asymmetric rolling on microstructures, mechanical properties, and intergranular corrosion behavior of Al-Mg-Si-Zn alloy

Effects of interrupted ageing(T6I6) and asymmetric rolling on microstructures, mechanical properties, and intergranular corrosion(IGC) behaviors of Al-Mg-Si-Zn alloy were investigated. Results showed that the T6 alloy has the lowest strength and the worst IGC resistance, while the T6I6 alloy has higher strength and better IGC resistance.What’ s more, the alloy treated by pre-rolling deformation has higher strength and better IGC resistance;and the alloy treated by the pre-asymmetry rolling achieves the highest strength, the best IGC resistance and lower elongation. The mechanical properties depend on microstructures such as the grain size, texture, dislocation density and precipitation, the grain boundary misorientation and grain boundary microstructure are responsible for the IGC resistance.

Rheological Properties of Conductive Asphalt Binders Containing Graphite and Carbon Fiber Before and After Ageing

Modified asphalt binders were prepared by adding conductive materials, graphite and carbon fiber. The rotation thin film oven test （RTFOT） and pressure age vessel test （PAV） were conducted to simulate the binder aging in the field. Rheological properties of graphite and carbon fiber modified asphalt binder were investigated by the empirically rheological properties （penetration and softening point） and the dynamic shear rheometer （DSR） test. Results show that physical properties of asphalt binder change with conductive material mixed. DSR tests present that the values of complex modulus increase while phase angles decrease under a proper amount of graphite and carbon fiber. Rutting parameters point out that graphite can improve the rutting resistance of asphalts. Rheological parameters can be used to assess aging.

Effect of ageing process on microstructure, corrosion behaviors and mechanical properties of Al-5.6Zn-1.6Mg-0.05Zr alloy

The influence of different ageing processes on the microstructure, corrosion behaviors and mechanical properties of extruded Al-5.6Zn-1.6Mg-0.05Zr(wt.%) alloy was studied in this work. The changes of morphology, size and distribution of MgZn_(2)precipitate with ageing temperature and time were revealed by optical and electron microscopy. Intergranular corrosion(IGC) and exfoliation corrosion(EXCO) tests were carried out to assess the changes in corrosion susceptibility of the tempered alloy, and some white spots on the surface of the sample aged for longer time were found to be precursors of pits. Electrochemical cyclic polarization test depicted the corrosion behavior under different tempers. Ageing influences on the mechanical behaviors of the alloy were revealed by evaluating its microhardness and tensile strength. The microscopic features of the strengthening phases determined by the ageing procedure directly affect the corrosion resistance and mechanical properties of the alloy.

Effect of Li addition on mechanical properties and ageing precipitation behavior of extruded Al-3.0 Mg-0.5 Si alloy

The effect of Li(2.0 wt%)addition on mechanical properties and ageing precipitation behavior of Al-3.0 Mg 0.5 Si was investigated by tensile test,dynamic elasticity modulus test,scanning electron microscopy(SEM),transmission electron microscopy(TEM)and high-resolution transmission electron microscopy(HRTEM)images.The results show that the tensile strength of the Li-containing alloy can be significantly improved;however,the ductility is sharply decreased and the fracture mechanism changes from ductile fracture to intergranular fracture.The elasticity modulus of the Li-containing alloy increases by 11.6%compared with the base alloy.The microstructure observation shows that the Li addition can absolutely change the precipitation behavior of the base alloy,andδ′-Al_(3)Li phase becomes the main precipitates.Besides,β′′-Mg_(2)Si andδ′-Al_(3)Li dual phases precipitation can be visibly observed at 170℃ ageing for 100 h,although the quantity ofδ′-Al_(3)Li phase is more thanβ′′-Mg_(2)Si phase.The width of the precipitate-free zone(PFZ)of the Li-containing alloy is much wider at the over-ageing state than the base alloy,which has a negative impact on the ductile and results in the decrease of elongation.

MICROSTRUCTURES AND PROPERTIES OF DZ40M Co-BASED SUPERALLOY AFTER LONG-TERM AGEING AT 850℃

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Evaluating the Influence of Ageing Temperature on the Mechanical Properties of Al-Mg-Si Alloy

The effect of ageing temperature on the mechanical properties of Al-Mg-Si alloy has been studied. The material was machined into different shapes of the tests to be carried out: tensile, impact and hardness. The test specimens were divided into two and, some sets were solution treated at 500℃ for one hour and peak aged at 160℃ for eight hours while the other sets were solution treated at 500℃ for one hour and peak aged at 180℃ for eight hours. The abovementioned tests were carried out on the specimens. The results show that at low ageing temperature of 160℃, the ductility and impact were high while at 180℃, the ultimate tensile strength and hardness are higher compared to the value obtained at 160℃.

The Effect of Ageing Time on Some Mechanical Properties of Aluminum/0.5% Glass Reinforced Particulate Composite

A particulate-hardened composite usually known as cermets with aluminum matrix and reinforced with ceramic particles from broken bottles was used to investigate the effect of ageing time on hardness and tensile strength. The samples used for the work were produced using stir-cast method and the samples were cast in metal moulds to improve on the surface finish and to obtain good cooling rate. The composite composition used was Al/0.5% glass particles. The samples were treated at 500?C and quenched in water at 65?C. They were then aged at various temperatures ranging from 150?C - 210?C. The result of the hardness test showed that within the range of the ageing time selected the hardness increased with the ageing for all the ageing temperatures used. Variations were observed but this is normal in ageing, particularly when coherent and incoherent precipitates are formed at a point in time, or when over-ageing occurs. The plot of the tensile strength tests and the hardness tests, with ageing time showed the trend as observed. The highest hardness value of 37.3 HRB occurred after 5 hours of ageing likewise the highest tensile strength value of 398.36 N/mm2 occurred after 5 hours of ageing at the same ageing temperature of 190?C. The aged composite showed improved hardness and tensile strength when compared to as-cast value of 23.7 HRB for hardness and 253.12 N/mm2 for tensile strength respectively.

Influence of aging on microstructure and mechanical properties of AZ80 and ZK60 magnesium alloys

The effect of aging on the microstructure and mechanical properties of AZ80 and ZK60 wrought magnesium alloys was studied with optical microscope and mechanical testers. The results demonstrate that both the tensile strength and elongation of AZ80 alloy increase firstly and then decrease as the aging temperature rises, the peak values appear when the aging temperature is 170 ℃ The hardness of ZK60 alloy increases firstly and then decreases as the aging temperature rises, and the hardness reaches its peak value at 170 ℃. However, the toughness of the alloy is just the opposite. Moreover, ZK60 alloy has good performances in both impact toughness and other mechanical properties at the aging temperature from 140 ℃ to 200 ℃.